Final report for US Green Building Council

Final report for US Green Building Council Project number: 332 Title: Development and implementation of a new protocol for testing the air quality implications of green building materials Prepared for project officer: Thomas Dietsche, Director Research Programs US Green Building Council Prepared by Principal investigator: Glenn Morrison Associate Professor of Civil, Architectural and Environmental Engineering 221 Butler Carlton Hall Missouri University of Science and Technology Rolla, MO 65409 (573) 341‐7192 [email protected] Co‐Principal Investigator: Richard L. Corsi, Ph.D., P.E. ECH Bantel Professor for Professional Practice Department of Civil, Architectural and Environmental Engineering The University of Texas at Austin [email protected] University of Texas, Austin Contributors: Clément Cros The University of Texas, at Austin Erin Darling The University of Texas at Austin Elliott Gall The University of Texas at Austin Seth Lamble Missouri University of Science and Technology 1
Contents Table of Figures ............................................................................................................................... 6 Executive Summary ......................................................................................................................... 9 1 2 Introduction ........................................................................................................................... 13 1.1 Research need ............................................................................................................... 16 1.2 Project study objectives ................................................................................................ 16 1.3 Outcomes ...................................................................................................................... 17 1.4 Tasks and milestones ..................................................................................................... 17 Project approach, materials and methods ............................................................................ 19 2.1 Study design .................................................................................................................. 19 2.2 Experimental overview .................................................................................................. 22 2.3 Material selection .......................................................................................................... 25 2.3.1 Material selection criteria ..................................................................................... 25 2.4 Task 1: Preparation, calibration and validation of preliminary chamber and analyses protocols .................................................................................................................................... 27 2.4.1 10 L S&T chamber protocol development ............................................................. 27 2.4.2 10 L S&T chamber and sampling protocol ............................................................. 29 2.4.3 S&T measurement of ozone, ozone deposition velocity and reaction probability 32 2.4.4 S&T primary and secondary emission rates, and product yield ............................ 33 2.4.5 48 L UT chamber and protocol .............................................................................. 36 2.4.6 UT measurement of ozone and ozone deposition velocity in 48 L chamber ........ 38 2.4.7 UT primary and secondary emission rates, and product yield .............................. 39 2.5 Task 2: Protocol Variations ............................................................................................ 41 2.6 Task 4: Materials preparation and testing in S&T 10 L chamber .................................. 42 2.6.1 General testing methods ....................................................................................... 42 2.6.2 General material preparation ................................................................................ 42 2.6.3 Material specific preparation ................................................................................ 42 2.7 Task 3a: Parallel lab validation ...................................................................................... 45 2.8 Task 3b: Field exposure and aging of selected materials .............................................. 46 2
2.8.1 Materials ................................................................................................................ 46 2.8.2 Field study ............................................................................................................. 46 2.9 2.9.1 Environmental Chamber ........................................................................................ 48 2.9.2 Materials ................................................................................................................ 51 2.9.3 Ozone Generation and Injection ........................................................................... 51 2.9.4 Ozone Measurement ............................................................................................. 51 2.9.5 By‐Product Sampling ............................................................................................. 51 2.9.6 By‐Product Analysis ............................................................................................... 52 2.9.7 Data Analysis ......................................................................................................... 52 2.10 Test House – Small Bedroom ................................................................................. 58 2.10.2 Ozone Measurements ........................................................................................... 60 2.10.3 By‐Product Sampling ............................................................................................. 61 2.10.4 By‐Product Analysis ............................................................................................... 61 2.10.5 Data Analysis ......................................................................................................... 61 Task 6: Grade development........................................................................................... 64 2.11.1 Primary emissions .................................................................................................. 65 2.11.2 Ozone removal potential ....................................................................................... 65 Project results and discussion ............................................................................................... 67 3.1 Task 1: Preliminary chamber protocol reproducibility .................................................. 67 3.1.1 S&T 10 L chamber .................................................................................................. 67 3.1.2 UT 48 L chamber .................................................................................................... 72 3.2 Task 2: Protocol variations ............................................................................................ 74 3.2.1 Carpet FC‐1 ............................................................................................................ 74 3.2.2 Clay plaster WCP‐1 ................................................................................................ 75 3.3 Task 4: Materials testing in S&T 10 L chamber ............................................................. 77 3.3.1 Results by material ................................................................................................ 77 3.3.2 Summary of results from19 materials in S&T 10 L chamber ................................. 97 3.4 Task 7: Field house measurements ............................................................................... 58 2.10.1 2.11 3 Task 5: Large chamber assessment of materials ........................................................... 48 Task 3a: Parallel lab comparison ................................................................................... 99 3
3.5 3.5.1 OZONE SCAVENGING ........................................................................................... 101 3.5.2 BY‐PRODUCT EMISSIONS ..................................................................................... 104 3.5.3 ASSOCIATION WITH ENVIRONMENTAL PARAMETERS ........................................ 108 3.6 Task 5: Large chamber assessment of materials ......................................................... 110 3.7 Large Chamber Experiments: Results .......................................................................... 110 3.7.1 Ozone deposition................................................................................................. 110 3.7.2 Primary Emissions ................................................................................................ 112 3.7.3 Secondary Emissions ........................................................................................... 116 3.7.4 Molar Yields ......................................................................................................... 119 3.8 Ozone deposition velocities ................................................................................ 122 3.8.2 Emissions ............................................................................................................. 124 3.8.3 Molar Yields ......................................................................................................... 127 Criteria for possible LEED credit and test method (Grade development) ................... 129 3.9.1 Impact on specific building .................................................................................. 129 3.9.2 Application of a specified limit concentration: ozone ......................................... 129 3.9.3 Application of a specified limit concentration: ozone reaction products ........... 131 3.9.4 Grading single materials: ozone .......................................................................... 134 3.9.5 Grading single matrials: ORPs .............................................................................. 135 3.9.6 Overview of parameters and metrics .................................................................. 137 3.9.7 Application of parameters and metrics to materials tested ............................... 138 Conclusions and recommendations .................................................................................... 140 4.1 Conclusions .................................................................................................................. 140 4.1.1 Materials tested .................................................................................................. 140 4.1.2 Test method and rating metrics .......................................................................... 141 4.2 Task 7: Field house experiments ................................................................................. 122 3.8.1 3.9 4 Task 3b Field Exposure and aging of selected materials ............................................. 101 Recommendations ....................................................................................................... 141 4.2.1 Target building materials for testing ................................................................... 141 4.2.2 Test methods and extrapolation ......................................................................... 141 4.2.3 LEED point(s) and metrics .................................................................................... 142 4
5 References ........................................................................................................................... 143 6 Appendices .......................................................................................................................... 146 6.1 Building material details .............................................................................................. 146 6.1.1 FC‐1 Carpet .......................................................................................................... 146 6.1.2 FC‐2 Carpet .......................................................................................................... 146 6.1.3 FRf‐1 Linoleum‐style tile resilient flooring .......................................................... 146 6.1.4 FRf‐2 Rubber puzzle‐locking tile resilient flooring ............................................... 146 6.1.5 FRf‐3 Bio‐based tiles, resilient flooring ............................................................... 147 6.1.6 FCf‐1 Porcelain floor tile ...................................................................................... 147 6.1.7 FWf‐1 Renewable wood flooring ......................................................................... 147 6.1.8 FWf‐2 Renewable wood flooring ......................................................................... 148 6.1.9 WC‐1 Cork wall tiles ............................................................................................. 148 6.1.10 WC‐2 Acoustical Wall Panels ............................................................................... 148 6.1.11 WC‐3 Fabric wall covering ................................................................................... 149 6.1.12 WP‐1 Latex paint and primer............................................................................... 149 6.1.13 WP‐2 Clay paint ................................................................................................... 149 6.1.14 WP‐3 Collagen paint ........................................................................................... 149 6.1.15 WCP‐1 Clay plaster .............................................................................................. 150 6.1.16 WD‐1 Recycled content drywall .......................................................................... 150 6.1.17 CP‐1 Ceiling tile .................................................................................................... 150 6.1.18 CP‐2 Ceiling tile .................................................................................................... 150 6.1.19 CP‐3 Ceiling tile .................................................................................................... 151 6.1.20 Latex drywall primer ............................................................................................ 151 6.2 S&T method for analyzing dinitrophenylhydrazine derivatives of carbonyls ............. 151 6.3 S&T method for analyzing thermally desorbed carbonyls from Tenax tubes ............. 153 6.4 Test house, detailed results ......................................................................................... 154 5
Table of Figures Figure 1‐1. Diagramatic representation of objectives and outcomes of this research ................. 16 Figure 2‐1. Depiction of ozone removal (R) and byproduct formation (P), where 1 refers to/from typical materials and 2 refers to to/from passive reactive panels. .............................................. 19 Figure 2‐2. Reduction of indoor ozone levels (C/Co) using PRMs. Removal terms correspond to those in Equation 2‐1. ................................................................................................................... 21 Figure 2‐3. 68 m3 stainless steel chamber for evaluating building materials under controlled, but natural conditions. Humidity, temperature and ventilation are controlled. ............................... 23 Figure 2‐4. Instrumented UTest house and floor plan. ................................................................. 24 Figure 2‐5 Diagram of 10 L experimental chamber system at Missouri S&T ................................ 30 Figure 2‐6 Image of 10 L chamber system. To the left are valves and mass flow meters that operate automatic DNPH and Tenax sample collection. To the right is the chamber with solenoid valves (i.e. bypass system) visible above the lid. .......................................................................... 30 Figure 2‐7 Operational timing for ozone activation, bypass and sampling. .................................. 32 Figure 2‐8: Experimental system used to test materials for inter‐laboratory validation and for assessment of materials exposed in field sites. ............................................................................ 37 Figure 2‐9. Organic gaseous compounds passive sampler ............................................................ 47 Figure 2‐10. Schematic of large environmental chamber for materials testing. .......................... 49 Figure 2‐11. Diagram of bedroom in UTest House that was used for experiments. ..................... 59 Figure 3‐1. Deposition velocity for every material and individual experiment derived from the 10 L chamber at Missouri S&T. ........................................................................................................... 67 Figure 3‐2. Fractional standard error as a function of the average deposition velocity. .............. 69 Figure 3‐3. Reaction probability for every material and individual experiment derived from the 10 L chamber at Missouri S&T. ...................................................................................................... 69 Figure 3‐4. Fractional standard error as a function of the average reaction probability. ............. 70 Figure 3‐5. Total yields for every material and individual experiment derived from the 10 L chamber at Missouri S&T. For clarity, these are not shown as speciated yields. ......................... 71 Figure 3‐6. Deposition velocity for every material and individual experiment derived from the UT 48 L chamber. ................................................................................................................................ 72 Figure 3‐7. Speciated yield for every material and individual experiment derived from the UT 48 L chamber. ..................................................................................................................................... 73 Figure 3‐8. The influence of chamber ozone concentration on deposition velocity and reaction probability for carpet FC‐1 ............................................................................................................ 74 Figure 3‐9. The influence of relative humidity, temperature and chamber ozone concentration on yield for carpet FC‐1. ................................................................................................................ 75 Figure 3‐10. WCP‐1 deposition velocity (left) and reaction probability (right) as a function of chamber ozone concentration. ..................................................................................................... 75 6
Figure 3‐11. WCP‐1 deposition velocity (left) and reaction probability (right) as a function of integrated ozone uptake. .............................................................................................................. 76 Figure 3‐12. Primary and secondary emission rates (left) and yields (right) for FC‐1, averaged over all replicates. ......................................................................................................................... 78 Figure 3‐13. Primary and secondary emission rates (left) and yields (right) for WP‐1, averaged over all replicates. ......................................................................................................................... 89 Figure 3‐14. Primary and secondary emission rates (left) and yields (right) for CP‐2, averaged over all replicates. ......................................................................................................................... 95 Figure 3‐15 All green building materials ranked by overall average deposition velocities. .......... 98 Figure 3‐16. Comparison of deposition velocities as measured on multiple pieces of carpet, ceiling tile and painted wallboard in two different laboratory chambers. ................................... 99 Figure 3‐17. Comparison of aldehyde yields from carpet, ceiling tile and painted wallboard for UT and S&T reactors. ................................................................................................................... 100 Figure 3‐18. Ozone deposition velocity on test material samples averaged over time. ............. 102 Figure 3‐19. Ozone deposition velocity on material samples averaged over all locations. ........ 103 Figure 3‐20. Ozone deposition velocities for ceiling tile. ............................................................ 104 Figure 3‐21. By‐product emissions averaged over all locations for all four test materials. ........ 105 Figure 3‐22. By‐product emissions for samples from the Kitchen location. ............................... 108 Figure 3‐23. Association graph for carpet by‐product emissions versus field air TVOC abundance.
..................................................................................................................................................... 109 Figure 3‐24. Ozone deposition velocity to background chamber and experimental materials. “Low” refers to low mixing condition and “High” refers to high mixing condition. Error bars are larger of propagated instrument error or standard error of the ozone decay regression summed with the background error. Raw data are presented in Appendix LC1. ...................................... 111 Figure 3‐25. Primary emissions of light aldehydes from background chamber surfaces and test materials. “Low” refers to low mixing condition and “High” refers to high mixing condition. Raw data and uncertainties associated with these measurements are presented in Appendices LC1 and LC2, respectively. .................................................................................................................. 114 Figure 3‐26. Primary emissions of heavy aldehydes from background chamber surfaces and test materials. “Low” refers to low mixing condition and “High” refers to high mixing condition. Raw data and uncertainties associated with these measurements are presented in Appendices LC1 and LC2, respectively. .................................................................................................................. 115 Figure 3‐27. Secondary emissions of light aldehydes from background chamber surfaces and test materials. “Low” refers to low mixing condition and “High” refers to high mixing condition. Raw data and uncertainties associated with these measurements are presented in Appendices LC1 and LC2, respectively. .................................................................................................................. 118 Figure 3‐28. Secondary emissions of heavy aldehydes from background chamber surfaces and experimental materials. “Low” refers to low mixing condition and “High” refers to high mixing condition. Raw data and uncertainties associated with these measurements are presented in Appendices LC1 and LC2, respectively. ....................................................................................... 118 7
Figure 3‐29. Molar yields of light carbonyls for background chamber surfaces and test materials. “Low” refers to low mixing condition and “High” refers to high mixing condition. Raw data are presented in Appendix LC1. ......................................................................................................... 119 Figure 3‐30. Molar yields of light carbonyls for background chamber surfaces and test materials. “Low” refers to low mixing condition and “High” refers to high mixing condition. Raw data are presented in Appendix LC1. ......................................................................................................... 120 Figure 3‐31. Molar yields of heavy aldehydes for background chamber surfaces and test materials. “Low” refers to low mixing condition and “High” refers to high mixing condition. Raw data are presented in Appendix LC1. .......................................................................................... 121 Figure 3‐32. Ozone deposition velocity to bedroom surfaces with and without ceiling tile and with no fan and fan in operation. SS refers to steady‐state conditions. .................................... 123 Figure 3‐33. Light aldehyde emission rates in bedroom with and without ceiling tile. BG refers to background (without ceiling tile) and CT refers to room conditions after ceiling tile was added.
..................................................................................................................................................... 125 Figure 3‐34. Heavy aldehyde emission rates in room with and without ceiling tile. BG refers to background (without ceiling tile) and CT refers to room conditions after ceiling tile was added.
..................................................................................................................................................... 126 Figure 3‐35. Light aldehyde molar yields for background room surfaces and to the room after ceiling tile was installed. .............................................................................................................. 128 Figure 3‐36. Heavy aldehyde molar yields for background room surfaces and to the room after ceiling tile was installed. .............................................................................................................. 128 Figure 3‐37. Odor and nasal pungency thresholds, reproduced from (Cometto‐Muñiz et al., 1998) ............................................................................................................................................ 133 Figure 3‐38. Graphical representation of how tested building materials compare against metrics for meeting proposed ozone control and byproduct prevention criteria. .................................. 139 8
Executive Summary The objectives of this project were to (1) develop measurement methods to evaluate green building materials for their ability to reduce ozone in buildings without a significant increase in ozone reaction products, and (2) to test those methods on a range of green building materials. The impact of real‐world environments and the relationships between results derived from different size chambers and a test house were also evaluated. Method development, assessment and application. Based on the recent laboratory investigations of ozone reactions with building materials and furnishings, chamber‐based methods were developed and tested. The resulting methods and protocols are a balance between obtaining high precision measurements (of deposition velocity, reaction probability, emission rates and byproduct yields) and limitations of existing analytical measurement methods. An inter‐laboratory comparison demonstrated that materials tested in different chambers (Missouri University of Science and Technology (S&T) and at the University of Texas, Austin (UT) generate qualitatively similar results for ozone uptake parameters. For materials that consume ozone readily (more desirable), the difference amongst chambers will primarily be due to mixing conditions. If these conditions are well characterized for a specific laboratory, it may be possible for different laboratories to report a uniform deposition velocity value for the same material. Secondary emissions and yield were not readily comparable between the two chambers. Differences in air exchange rate, analytical quantification limits and lab‐specific background contamination may account for some of these differences. Parameter variations on two materials did not show any significant change in tested parameters over the tested temperature or humidity ranges. However, a significant reduction in byproduct yield was observed in the UT large chamber at high relative humidity for one carpet. The measured deposition velocity and reaction probability tend to diminish as the chamber concentration of ozone increases. Based on the combination of small, medium and large chamber experiments, we conclude that chambers of at least 10 L in volume, operated at 25 C and 50% RH with an internal ozone concentration in the 50‐100 ppb range should adequately generate reliable ozone uptake (deposition velocity, reaction probability) values that can be extrapolated to real‐world settings. Larger chambers may be better and may allow for more precise measurements and more appropriate air exchange rates. Materials testing. Nineteen green building materials were tested using a 10 L chamber. Several materials exhibited very high ozone removal rates (deposition velocities > 3 m h‐1): carpets, 9
acoustical wall panels, a clay‐based paint, a clay plaster, bare drywall and 2 ceiling tiles. Of these, the carpets, clay‐based paint, wall panels and ceiling tiles appear to provide organic reaction sites that result in secondary emissions of carbonyl compounds. The others appear to remove ozone by an inorganic reaction, perhaps catalytic. Recycled rubber floor tiles, a fabric wall covering and a perlite ceiling tile exhibited moderate ozone uptake rates (deposition velocity ~ 1‐3 m h‐1). The rest of the materials tested exhibited low ozone removal rates (deposition velocity <1 m h‐1). The low rates were associated with glazed porcelain tile, finished wood and two paints. Most of these materials have little intrinsic surface area, at least as evidenced by a smooth appearance. Field testing. A subset of the materials (one carpet, one type of ceiling tile and one type of latex painted wall‐board) were placed in various field settings (kitchen, office, bedroom, etc.) and periodically tested for deposition velocity and byproduct emission rates. A key finding was that the tested materials generally sustain their ability to remove ozone over at least six months. Some materials can lose their ability to consume ozone however. Carpet exhibited the most significant reduction in ozone removal rates (parameterized by deposition velocity) over six months. Averaged over all locations, the deposition velocity dropped from 3.3 m h‐1 to 2.3 m h‐1. For other materials, the reduction was very small, suggesting that initial chamber measurements may be adequate to describe long‐term behavior. Ceiling tile appears to be the best of the three materials in terms of exhibiting a large ozone deposition velocity and low by‐product emissions; it surpasses carpet in terms of reactivity during the study. Placement of materials near or in a kitchen affects secondary emissions from the material itself. Based on other studies, this is likely due to soiling of the materials with cleaners and cooking oils. Even highly ranked materials may become sources of secondary emissions unless they are placed away from likely sources of contamination in buildings. Ambient concentrations of volatile organic compounds in building air can affect primary and secondary emissions from materials, again suggesting a form of on‐
site modification of the surfaces that must be considered in future research. Large (room‐sized) chamber testing. A subset of the materials (one carpet, one type of ceiling tile and one type of latex painted wall‐board) tested in the 10 L chambers were tested at full‐
scale in a well controlled 68 m3 chamber at UT. In this chamber, materials were subjected to three different relative humidity conditions and two different mixing conditions. Under each condition, the ozone removal rate (parameterized by the deposition velocity) and ozone reaction product yields were measured. We observed high ozone deposition velocity to carpet (5.5 to 7.4 m h‐1), moderate for ceiling tile (1.9 – 2.6 m h‐1), and low for painted drywall (0.20 – 0.65 m h‐1) and chamber surfaces (0.01 ‐ 0.33 m h‐1) . These deposition velocities are similar in scale to those derived from the 10 L chambers at Missouri S&T (4.9, 2.1 and 0.74 m h‐1 for carpet, ceiling tile and painted drywall respectively), but deviate somewhat from those derived from the 48 L chamber (carpet is a bit lower at 3.3 m h‐1, ceiling tile is about the same at 2.6 m h‐1, and paint is a bit higher at 1.3 m h‐
10
1
). Carpet generated moderate primary and secondary emissions, with the majority in the form of aldehydes, especially nonanal. We observed low to insignificant primary and secondary emissions from chamber walls, ceiling tile, and paint (with one outlier for paint). Higher mixing intensity resulted in higher ozone removal (and higher deposition velocities) to carpet, but inconsistent results for other materials. The relative humidity had little effect on ozone deposition velocities but appeared to affect primary and secondary emissions (of heavy aldehydes) from carpet. In this case, high relative humidity (RH = 75% ) resulted in lower emissions. This observation suggests that chamber RH conditions are important for a standardized test method. Field house (UTest house). The field testing above was intended to quantify the impact of real indoor environments on the performance of the materials themselves. A second set of experiments (in a well instrumented, fully operational test house on the research campus of the University of Texas) was intended to measure the impact of a highly ranked material on the indoor environment itself, specifically its ability to reduce indoor ozone concentrations and byproduct emission rates. A ceiling tile composed of perlite had been identified as promising and was used to measure the impact of an intentionally reactive panel. Our results were promising but somewhat inconclusive. Ozone removal rates did not appear to be significantly increased with the addition of perlite‐based ceiling tiles. This is likely due to the relatively high background reactivity of the room that was used in the UTest House. Thus, covering a highly reactive material with another will not significantly improve ozone concentrations. However, the ceiling tiles did appear to reduce the secondary emission rates of carbonyl compounds in some cases, likely by reducing the total ozone flux to other surfaces. Based on later measurements in 10 L chambers we learned that other materials, such as clay plaster, may have performed better. Metrics for rating and ranking materials. The installed materials should improve indoor air quality, specifically reducing indoor concentrations of outdoor derived ozone and indoor derived reaction byproducts. There are no promulgated indoor ozone concentration standards in North America. But applying standards under consideration and also by developing minimum byproduct emission rate limits based on odor threshold analysis, we developed numerical limits for ranking both individual materials and “as installed” in buildings. This analysis included the basic framework/model for indoor air concentrations of reactive pollutants. A minimum of two parameters are necessary to promote ozone removal and prevent byproduct emissions. We suggest that, for commercial buildings, the chamber‐measured deposition velocity (vd) multiplied by the typical area‐to‐volume ratio of the installed material (A/V = area of material divided by volume of indoor space) should be in the range of >2‐3 h‐1, but can be more precisely defined for material type (floor, ceiling, walls). Multiplying the above parameter by the total byproduct (molar) yield (y) generates a new parameter that limits carbonyl emissions indoors. We suggest that vd(A/V)y < 0.1 h‐1 or if measurement sensitivity is not sufficient, < 0.3. 11
Of the materials tested, only a few met the recommended criteria. Clay wall plaster easily met all criteria with substantial ozone removal rates and zero byproduct emissions. Unpainted drywall and two ceiling tiles were close, but exhibited a small amount of byproduct emissions. Most others either were insufficiently reactive (low ozone removal rates) or produced copious amounts of undesirable reaction byproducts. Given that the test method is likely to be somewhat more expensive and time consuming than existing emission testing methods, manufacturers may want to be selective in the materials that they want rated by this method. Porous inorganic materials, such as brick, clay, stucco, concrete and other mineral based or refractory materials, are more likely to pass the criteria for high ozone removal rates and low byproduct (secondary) emission rates.
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1 Introduction A key requirement of green buildings is to provide occupants with a healthy, productive space. Indoor air quality is vital to health and productivity as recognized by the Indoor Environmental Quality component of Leadership in Energy and Environmental Design (LEED). To ensure a healthy environment, buildings are designed, maintained and operated to minimize pollution sources while providing sufficient ventilation to remove contaminants and meet or exceed standards for fresh air, such as ASHRAE standard 62.1. A conceptual diagram of this philosophy is shown in Figure 1. Sources of pollution, such as volatile organic compound (VOC) emissions from carpet and cleaners, increase levels of pollutants in buildings while sinks (e.g. ventilation) act to decrease levels. Sources and sinks can also be categorized as passive (requiring little or no on‐site energy input) or active (requiring on‐site energy). Within the context of indoor air quality, green buildings should reduce sources and maximize sinks, and do so while minimizing energy use. sources
s
m
o
g
sinks
VOCs: Carpet,
Cleaners, Adhesives
Composite wood
Building materials
Smog: Natural
ventilation
Natural ventilation
passive
Mechanical
ventilation
Smog: Mechanical
ventilation
Filtration
active
FIGURE 1. Control of indoor air pollution through reduction of sources, and application of sinks, such as ventilation, filtration and building surfaces. While ventilation acts to remove internally generated pollutants (a sink), it also draws in outdoor air pollution (a source). Outdoor pollutants are difficult to control in buildings because a minimum amount of “fresh” outdoor air is required (LEED EQ prerequisite 1); indoor smog levels are particularly problematic during the work day when photochemical smog levels are highest and when commercial buildings are at high occupancy, requiring high ventilation rates. Ozone, a key outdoor smog component responsible for thousands of deaths each year (Bell et al., 2006), can be controlled by installing activated carbon filtration in mechanically ventilated buildings. But this has been used sparingly due to increased replacement costs, the slow acceptance of new technologies and the energy penalty associated with increased filtration. Other than 13
natural ventilation (which acts as both a source and sink of smog), there are no passive, low‐
energy, air pollution sinks recognized by any Green Building criteria. Yet, all buildings incorporate passive pollution sinks, even if architects, owners, and occupants do not recognize them as such. All interior building surfaces consume and remove some ozone (and other pollutants). For example, glass and vinyl flooring are relatively poor ozone sinks while carpet and other fleecy surfaces consume ozone readily. For a typical carpeted room of 150 ft2 (15 m2), carpet removes ozone at a rate equivalent to activated carbon filtration at 14 cfm (23 m3 h‐1); this is nearly the recommended fresh air delivery rate of ~20 cfm per person. Carpet is reasonably effective, but other materials can exhibit even greater removal rates per unit area. Considering walls, ceilings and floors, the potential for passive pollutant removal is large, estimated at 230 cfm (400 m3 h‐1) of filtered air for a single room. Therefore, existing building materials and furnishings are an incredibly valuable untapped resources for removing pollutants, and do not require additional energy for filtration. Yet high ozone consumption comes with a price. Ozone reactions with some surfaces generate carcinogens (formaldehyde, acrolein), irritants (carbonyls, dicarbonyls, acids), free radicals, and other oxidation products of concern (see review in Weschler, (2004)). The volatile ozone reaction products (ORPs) have been coined “secondary emissions”, and the resulting concentrations of chemical reaction products are large enough to have health and comfort consequences at typical indoor ozone levels. Weschler et al. (2006) suggests that mortality and morbidity correlations reported by Bell et al. (2006) may, in large part, be due to indoor exposure to ozone and its reaction products. Existing test methods fail on several accounts to protect occupants from chemically generated pollutants. Ozone reacts with materials, typically generating a wide range of aldehydes and other oxygenated chemicals. LEED EQ credit 4.1 considers aldehyde emissions, with a concentration limit of 0.1 mg m‐3. Most modern carpets can pass this criterion, but when installed, ozone reacts with oils on the surface (Morrison and Nazaroff, 2002), chemically generating aldehydes. Some carpets (e.g. CP3 in Morrison and Nazaroff, 2002) will generate summed aldehyde emission rates in excess of the EQ credit 4.1 test limit, but only after it is installed and exposed to typical indoor levels of ozone. Other carpets (e.g. CP1 in Morrison and Nazaroff, 2002) may not exceed this limit. A further problem with chemically generated secondary emissions is that they can be released for extended periods of time: years to decades. Traditional airing out periods will not suffice to remove this source of pollution. Preventative ozonation of materials before installation is also not recommended because oxidized compound emissions persist and are released long after ozone has been removed.
Thus, building materials that remove ozone (or other pollutants) without generating objectionable byproducts are highly desirable for Green Buildings. This passive approach to 14
contaminant removal is particularly compelling given the fact that at least a third of US buildings do not have central forced‐air heating or cooling systems (Census, 2005). Residences that do have such systems often operate them on a thermostat with typical duty cycles of 10 – 20 minutes per hour or less, suggesting that ozone filtration in the central system may have no effect during most of the day. The focus of this research is a zero‐energy approach that will be particularly attractive in the design of new commercial buildings that rely on passive ventilation for part of the year. The principal investigators focused on ozone in this research because it is toxic, its source is effectively uncontrollable (outdoor smog), it is otherwise difficult to remove without additional mechanical filtration and its reactions with building materials generate VOC emissions that can cause an acceptable green material to become unacceptable by existing standards. Other pollutants, such as formaldehyde, may be suitable targets for future passive control methods. At present, no test method has been developed for the purposes of allowing architects and others to choose materials for their ability to clean the air of ozone without generating substantial byproduct emissions. A handful of building surfaces (such as carpet, glass, concrete, painted and unpainted wallboard, HVAC components) have been evaluated at the bench scale for their ozone reactivity (Bekö et al., 2006; Grøntoft and Raychaudhuri, 2004; Hyttinen et al., 2006; Kleno et al., 2001; Morrison et al., 1998; Poppendieck et al., 2007) and even fewer have been tested for ORP generation (Morrison and Nazaroff, 2002; Morrison et al., 1998; Poppendieck et al., 2007; Reiss et al., 1995). This research results in a readily applied test method and recommends several possible metrics for promoting materials to architects, and for promoting Green Buildings to owners and occupants. 15
1.1 Research need Interior building surfaces impact air quality, positively and negatively, in ways not accounted for by existing test protocols or certification criteria. Many green buildings may already passively clean the air; others may unintentionally engender poor air quality. Ozone is specifically targeted in ASHRAE standard 6.2.1.3 (2007 draft) stating that “air cleaning devices for ozone shall be provided…”. Outdoor air filtration is specifically recommended, but architects, engineers and designers should also have clear guidance on what materials can be used to passively reduce indoor smog levels without generating unwanted, irritating VOCs. At present, there is no test method or grading scale to allow for this determination. This research project has direct relevance to item 4.1 Indoor Environmental Quality (IEQ): Pollutants and Stressors as described in Chapter 4 of the USGBC Research Committee’s A National Green Building Research Agenda. Specifically, the project addresses two of the stated general research topics: (1) “Clarify the chemistry, biology and mechanics of indoor environmental quality (IEQ) to inform improvement strategies,” and (2) “Develop metrics and tools to quantify indoor conditions and simplify the processes of understanding, assessing and improving IEQ.” More specifically, it directly addresses Priority topic 3 to “Develop more effective standards and protocols for product emissions testing.” 1.2 Project study objectives smog
This project develops
methods to rank green
building materials for
their ability to passively
remove smog from
interior spaces
Figure 1‐1. Diagramatic representation of objectives and outcomes of this research The primary goal of this project is to provide professionals in the green building industry with novel criteria for the selection of materials that are low‐emitting, and that also reduce indoor 16
levels of ozone. Figure 1‐1 shows, in a single drawing, the primary objective and outcomes of this project. The specific objectives of this project are to: 1. Develop a novel test protocol and grading scale that characterizes green materials for their primary emissions, ozone removal capacity, and secondary emissions related to material‐
ozone reactions. 2. Perform a series of tests on a wide variety of green building materials, and employ the new grading scale to evaluate these materials. 1.3 Outcomes This research provides clear metrics for choosing materials to significantly improve building air quality (influence building practices and/or performance) without increasing the energy required for mechanical filtration or ventilation (advance sustainability of buildings). Ozone and its reaction products are a serious health hazard in urban areas; buildings that passively control for these pollutants not only protect the occupant but may even reduce premature death associated with ozone exposure (economic, energy, environmental, and social benefit). A clear grading scale provides designers with unambiguous criteria for choosing materials, marketing designs to clients and meeting future LEED criteria (influence practice). 1.4 Tasks and milestones Specific tasks (from the original proposal), and milestones associated with the task, are outlined below. Modifications to the original tasks or milestones are indicated in bold. Task 1. Preparation, calibration and validation of preliminary chamber protocol. In both the Missosuri S&T labs and UT labs, the initial chamber protocol will be prepared. Specifically, we will assess negative and positive controls, reproducibility, analyte collection efficiency, calibration of instrumentation, etc. Milestone: preliminary chamber protocol able to reproducibly quantify ozone reaction probability and C1 through C12 aldehyde yields for two green building materials. Task 2. Protocol variations. Based on lessons learned from initial protocol preparation, protocol variations will be assessed in Missouri S&T chambers. These are anticipated to include length and conditions of air‐out period, ozone concentration, humidity, temperature, length of exposure, and soiling but may include other factors as they become apparent. These tests on a subset (~3‐4) of materials are intended to refine the test protocol and evaluate the potential uncertainty associated with variable conditions in buildings. Milestones: quantification of the impact of protocol variables and a refined protocol. The variables tested in this research were ozone concentration, humidity, length of exposure (in primary protocol variations in small 17
chambers). The impact of air mixing, and real‐world soiling were tested in the large UT chamber and in field tests. Task 3.Simulated field exposure and parallel lab validation of protocol. Task 2 is designed to assess protocol parameters. In Task 3, UT will test several materials in parallel with MS&T in their small chambers to compare results. It is also important to evaluate the impact of diurnal ozone concentrations and long exposures times on materials. Due to limited chamber availability, a single UT chamber will be dedicated to long‐term (e.g. months) exposure of several materials. The results will be compared against the shorter term protocol evaluation. Milestone: results from simulated field exposure, and parallel protocol tests, are shown to be consistent with MS&T short‐term, small‐chamber measurements. Instead of using a chamber for “simulated” exposure, we chose to put more materials into multiple field sites for a 6‐
month real‐world exposure assessment. Task 4. Materials testing. The small Missouri S&T chambers will be used to test and grade as many materials as possible, with a target of 20 materials delivered directly from the manufacturer. The total number will depend on the time required to apply the refined protocol to each material. Milestone: Up to 20 green building materials will be tested for ozone removal potential and secondary emissions. A total of 19 materials were tested in the S&T small chamber. Task 5. Large chamber assessment of single and mixed materials. The 70 m3 chamber at UT will be used to assess the impact of several individual and combined materials, under full‐scale, but controlled conditions. Milestone: Indoor air quality model predictions from small chamber protocol assessment are consistent with full‐scale chamber results. Combined materials were not tested due to limited resources. Task 6. Grade development. Based on on‐going experiments and input from stakeholders and the USGBC, we will develop a practical grading scale for green building materials. Milestone: grading scale finalized and applied to materials tested. Task 7. Field house measurements. Highly ranked materials will be installed in one or more rooms of the UT test house and their impact on ozone and secondary oxidation products will be assessed. Milestone: a significant reduction in the ratio of indoor to outdoor ozone concentrations, without significant increases in aldehyde levels, after installation of materials. This milestone was not met due to high background reactivity in the UT test house. The experiments did show improvements in ozone uptake with a “highly ranked” material, but the effect was difficult to discern against background reactivity. Task 8 and milestone: Final Technical Report. 18
2 Project approach, materials and methods 2.1 Study design Conceptual Framework. It is instructive to describe the conceptual engineering framework that is used to model indoor levels of ozone and ORPs. For simplicity this analysis is based on the assumptions of a well‐mixed home under steady‐state conditions with natural ventilation; for commercial buildings, the analysis is similar but may include individually ventilated compartments. Green materials intentionally designed into a building for the removal of ozone or other pollutants are coined Passive Reactive Materials (PRMs). C
Co
Q
Cp
Cp
C
R2
R1
Q
P2
P1
Figure 2‐1. Depiction of ozone removal (R) and byproduct formation (P), where 1 refers to/from typical materials and 2 refers to to/from passive reactive panels. A simplified depiction of ozone removal and byproduct formation in a home is shown in Figure 2‐1. Outdoor ozone enters the building by infiltration, as depicted by the outdoor ozone concentration (Co) and volumetric flow rate of outdoor air into the home (Q). Within the home ozone is removed by reactions with interior materials (R1), producing oxidized byproducts (P1). These reactions lead to a lower indoor ozone concentration C relative to the outdoor concentration (C/Co < 1), as well as increasing the indoor concentration (Cp) of these products. The inclusion of PRMs leads to additional ozone removal (R2) and, if chosen properly, only negligible amounts of additional byproducts (P2). The positive effects of PRMs are twofold. First, they lead to a reduction in the indoor ozone concentration and, hence, occupant exposures to ozone. Second, a lowering of indoor ozone via reactions at PRMs (R2) leads to less ozone available for reactions with other materials (R1), and a corresponding reduction in byproduct formation (P1) and concentration (Cp). 19
The following equation describes the ratio of indoor and outdoor ozone concentrations, based on a steady‐state ozone molar (or mass) balance on the home in Figure 2‐1: C
=
Co
1
⎫
1⎧
1 + ⎨∑ vd ,i Ai + vdr ,PRM APRM ⎬
Q⎩ i
⎭
Term 1 Term 2 2‐1 where, C and Co are the indoor and outdoor ozone concentrations, respectively (ppb), Q is the volumetric air flow rate (infiltration rate) through the occupied portion of the home (m3 hr‐1), vd,i is the ozone deposition velocity for material i (m hr‐1), Ai is the area of material i (m2), vdr,PRM is the ozone deposition velocity for a PRM (m hr‐1), APRM is the area of the PRM (m2). Terms 1 and 2 are volumetric removal rate terms associated with ozone removal at existing surfaces and at the PRM surfaces. Note that buildings are never at true “steady‐state”; equation (2‐1) is instead illustrative of the relative impact of each parameter on time‐averaged indoor concentrations (Riley et al, 2002). An increase in Term 2 can be achieved by increasing either the ozone deposition velocity or area of the passive reactive material. The deposition velocity is a “mass transfer coefficient” that is related to the rate that ozone can transport to and react with the surface of a building material. Insight into the role of physical and chemical processes on deposition velocity can be gleaned by noting that the overall resistance to ozone removal to a material is the inverse of deposition velocity, and is composed of terms that reflect resistances due to transport to the surface (fluid mechanics) and reactions at the surface (surface chemistry) as shown by Equation 2‐2. Ω=
1
1
4
= +
v d vt
vb γ
2‐2 where, Ω is the overall resistance to ozone removal to a material (hr/m), vd is the deposition velocity for a material (m/hr), vt is the transport‐limited deposition velocity to a material (m/hr), <vb> is the Boltzmann velocity for ozone (m/hr), and γ is the reaction probability (number of reactions per number of collisions with material) for ozone and a specific material (dimensionless). Thus, the overall resistance to ozone removal at a passive reaction panel can be decreased, or conversely deposition velocity increased, through enhanced transport to the material (fluid mechanics), i.e., increased vt, and the use of materials that are highly reactive with ozone, i.e., increased γ. Shown in Figure 2‐2 is an example of the anticipated reduction in 20
C/Co due to replacing half the wall/ceiling surfaces with PRMs in a typical home. We use typical values of Q, vt, A, γ for carpet, walls, and other surfaces, and γ = 5 × 10‐5 for what we would consider an “effective” PRM. Also shown are the relative removal terms (Terms 1 and 2 in equation (1)), in units of m3 h‐1 for each surface. Note that replacing some walls with panels results in a small reduction in the wall removal term, but a very large enhancement in removal due to the PRM removal capacity. Thus, it is possible to substantially reduce indoor levels of ozone with only partial replacement of well‐chosen wall materials. C/Co
0.2
0.1
indoor levels reduced by > 50%
1200
Figure 3. Reduction of indoor ozone levels (C/Co) using PRMs. Removal terms correspond to those in Eq. 1. 0.0
700 cfm
3
-1
removal term (m h )
1000
PRM
800
600
walls, ceiling
400
other
carpet
200
Q, infiltration
0
typical building
with PRM
Figure 2‐2. Reduction of indoor ozone levels (C/Co) using PRMs. Removal terms correspond to those in Equation 2‐
1. The net increase in ozone reaction product (ORP) concentrations, ΔCp, above levels due to other sources, is given by Equation 2‐3: ΔC p =
⎫
1⎧
⎨∑ yi vd ,i Ai + yrp vd , rp Arp ⎬C Q⎩ i
⎭
Term 1 2‐3 Term 2 where yi is the byproduct molar yield associated with ozone reactions with indoor materials other than PRMs, and yrp is the byproduct molar yield for ozone reactions with PRMs. Term 1 corresponds to P1 in Figure 2‐1 and Term 2 to P2. Use of PRMs will tend to reduce Term 1, relative to an uncontrolled building, by replacing existing surfaces. For example, the carpet in Figure 3 could be replaced with glazed floor tile to reduce ORP generation and more PRM materials included on walls and ceiling to balance the reduced ozone consumption associated with the floor tile. Note that the indoor byproduct concentration could also be reduced by 21
increasing the volumetric flow rate (Q) through the building. However, this leads to higher indoor ozone concentrations and, thus, to greater ozone exposure. Two key parameters associated with building surfaces emerge from this analysis: the ozone‐
surface reaction probability, γ, and the byproduct yield, y. It is these two parameters that will be the primary subject of test protocols. From these, grading scales can be developed that use terms more familiar and useful to those specifying materials in buildings. 2.2 Experimental overview Experimental. Eight tasks and milestones are outlined in section 1.4. Here we briefly explain experimental details and refer to specific tasks as appropriate. The lead university is shown in parentheses (MS&T = Missouri University of Science & Technology; UT = University of Texas at Austin). Small chamber studies (MS&T). Green building materials were evaluated at MS&T in 10 liter stainless steel chambers. The specific research objective was to reproducibly determine the steady‐state reaction probability and product yields (imbedded in equations 2‐2 and 2‐3) for 10 to 20 materials. We selected materials that generally compose large surface areas in either or both residential and commercial buildings, particularly floor, wall, and ceiling materials. We drew on materials from lists available for low‐emitting materials, such as the Collaborative for High Performance Schools Low Emitting Materials Table. We also included materials that were no yet be listed, but that are anticipated to be particularly ozone reactive including bamboo flooring, inorganic perlite‐based ceiling materials, cork wall coverings, and renewable bio‐based materials such as collagen paint. See section Error! Reference source not found. for a detailed list of materials chosen. Small chamber protocols were based on experience and well‐established protocols in peer‐
reviewed literature (Morrison and Nazaroff, 2002; Morrison et al., 1998; Wang and Morrison, 2006). Details are found in section 2.4.1. Tasks 1, 2 and 4 are all related to the experimental work done in small chambers at S&T. Small chamber studies (UT). Several materials (3 minimum) were sent to UT as an interlaboratory study for test‐protocol comparison and validation in 48 liter chambers. (Task 3) Field tests. To assess the long term effects of “real world” conditions on these materials, UT undertook long‐term testing for a group of materials. The materials were placed in homes and offices and allowed to age and soil for 6 months. Before, during and after this exposure episode, small‐chamber protocol measurements of deposition velocity, primary and secondary emissions and yield were measured.
Large chamber experiments (UT). For a subset of materials identified through MS&T small chamber experiments, full‐scale assessment were completed in a state‐of‐the‐art 68 m3 climate‐
22
controlled stainless steel chamber that can be used to simulate large room‐sized environments. The chamber is well instrumented with 16 omni‐directional and five three‐dimensional hot‐wire anemometers for velocity and turbulence intensity measurements, and 120 precision temperature and 10 relative humidity sensors. Supply and exhaust ducts for the chamber are equipped with flow sensors, as well as sampling ports for ozone analyzers. The chamber air exchange rate can be precisely controlled from 0.5 to 15 air changes per hour (ACH). UT researchers used pulse injection of ozone and measured its decay to determine the removal rates of installed materials (instead of steady‐state analysis typical of the small chambers). This allowed for determination of an ozone decay rate, and the area‐specific ozone removal rate for reactive materials by subtraction of the decay rate for experiments with panels from those without. The ozone decay rate is then used to determine the spatial extent of reaction panels necessary per volume of interior space in order to achieve a desired fractional reduction in indoor ozone. Experiments were completed at three RH conditions (20%, 50%, 80%) and under low and high mixing conditions. Figure 2‐3. 68 m3 stainless steel chamber for evaluating building materials under controlled, but natural conditions. Humidity, temperature and ventilation are controlled. 23
Test house experiments (UT). A unique test house facility (Figure 2‐4) was used to examine the impact of these materials in a real building. The UTest House is a fully‐instrumented 3 bedroom/2 bath 115 m2 manufactured home with two independent HVAC systems and with remotely controlled seven port CO2 injection and monitoring systems for continuous air exchange measurement, two outdoor weather stations, and several pressure, temperature, and RH measurement stations throughout the house and HAC systems. In these experiments, ozone and byproduct concentrations (and also deposition rates and emission rates) were measured with and without PRM material installed. Figure 2‐4. Instrumented UTest house and floor plan. 24
2.3 Material selection 2.3.1 Material selection criteria We originally proposed to select materials that generally comprise large surface areas in either or both residential and commercial buildings, particularly floor, wall, and ceiling materials. To ensure that we had a suitable cross‐section of materials, we generated an initial list of materials that 1. consume ozone at high or low rates, and/or are likely to release secondary byproducts at high or low rates, and 2. are typically installed in buildings such that they cover a large surface area and are exposed to occupied spaces (these materials cover walls, ceilings or floors and are most likely to be advantageous in removing pollutants by passive mass‐transfer since the rate of removal is directly proportional to surface area, all else being equal), and 3. are specifically listed in the Collaborative for High Performance Schools Low Emitting Materials Table, or are reported by the manufacturer to meet a certified test method for low‐emitting materials and may be used for LEED credits, and 4. are made by both large and small manufacturers, and 5. include materials with recycled content and/or renewable content We enlisted the Technical Review Team to help us refine the initial list (Table 2‐1) through emails and a teleconference. Based on this process we generated the following list of materials, their reported or assumed “green” characteristics, etc. 25
Table 2‐1. List of building materials tested in S&T 10L chamber. Details in Appendix 7.1 ID FC‐1 FC‐2 Manufacturer Interface flooring Shaw Surface
Flooring
recycled backing carpet
fabric backed carpet
FRf‐1 Forbo FRf‐2 FRf‐3 FCf‐1 FWf‐1 FWf‐2 WC‐1 WC‐2 Rubber Products Armstrong American Olean EcoTimber Smith & Fong unknown (Portugal) Golterman & Sabo WC‐3 WP‐1 WP‐2 Carnegie Fabrics Benjamin Moore Bioshield Marmoleum resilient tile puzzle‐locking tiles
bio‐based resilient tiles
porcelain clay tile
finished hardwood floor
finished bamboo floor
Walls
cork wall tiles
fabric acoustical wall panel fabric wall covering
latex paint and primer
clay based paint
WP‐3 EcoTrend collagen based paint
Composition
Green Attribute1
Intended Usage
response2
nylon, glasbac backing
nylon, softbac platinum backing linoleum substitute
recycled, CHPSLEM
recycled, CHPSLEM
commercial
commercial
+ +
+ +
renewable, CHPSLEM
commercial
+ +
recycled rubber
no information
sealed porcelain clay
hardwood composite
Bamboo composite
recycled
renewable, CHPSLEM
likely low‐emitting
renewable
renewable
commercial
commercial
commercial
dual
dual
+ +
+ +
+ - - -
cork
fiberglass, fabric
renewable
renewable
commercial
commercial
+ +
+ +
xorel fabric, paper acrylic latex
Clay, pigments, cellulose, binders amino acrylic resin with collagen binder Clay, pigment
gypsum
renewable
Low VOC, Greenguard
likely low emitting
commercial
dual
dual
+ +
- + -
Low VOC Greenguard
dual
+ +
WCP‐1 American Clay clay plaster wall coating
Likely Low Emitting
dual
WD‐1 USG drywall
Recycled
dual
Ceilings
CP‐1 Armstrong mineral fiber ceiling tile
mineral fiber, binders
CHPSLEM
residential
CP‐2 Chicago Metallic perlite ceiling tile
perlite
Likely Low Emitting
commercial
CP‐3 Certainteed fiberglass ceiling tile
Fiberglass, binders
CHPSLEM
commercial
1
(CHPSLEM) Collaborative for High Performance Schools Low Emitting Materials Table
2
originally anticipated material response: high ozone removal or byproduct emissions (+), low removal or emissions (-); optimum is [+ -]
26
+ + - + - -
2.4 Task 1: Preparation, calibration and validation of preliminary chamber and analyses protocols 2.4.1 10 L S&T chamber protocol development Each laboratory chamber used for ozone uptake and primary and secondary emissions testing should meet several overarching criteria: •
•
•
Reproducibility and precision in desired metrics Low or insignificant chamber related effects on outcomes (e.g. reactive chamber surfaces) Commercial laboratories should be able to apply the methods developed. The 10 L S&T chamber has been used for studying ozone reactions on building materials for many years. Based on this experience, and lessons learned by other laboratories studying similar phenomena, a basic design for experimental conditions, timing and measurements has been established. At its core, a 10 L cylindrical stainless steel chamber houses a material to be tested. The chamber has two ports: inlet and outlet. Pure air at a constant relative humidity flows through the chamber. Primary emission rates of target carbonyl compounds are measured by drawing a sample from the outlet of the chamber in the absence of ozone. After analysis of that sample, the mass of each carbonyl compound collected is divided by the cross‐section (or projected) area of the building material sample and the time over which the sample was collected, resulting in a primary emission rate in units of μg m‐2 h‐1. Secondary emission rates are measured in a similar fashion but in the presence of ozone. Secondary emission rates are simply the emission rate measured in the presence of ozone minus the primary emission rate. Ozone uptake is measured in several ways (see section 2.4.3 for details), but broadly the difference between inlet and outlet ozone concentrations can be related to two key parameters of interest: the deposition velocity and the reaction probability. Designing chamber dimensions, system flow rates and measurement parameters and methods requires a balance of competing requirements. For example, low flow rates tend to increase the primary carbonyl concentrations at the exhaust which can improve sensitivity for primary emission rates. Low flow rates can also reduce the outlet ozone concentration relative to that at the inlet, improving sensitivity for ozone uptake parameters. Given the small size of the chamber, simulating the air exchange rate typical of buildings, also suggests that the flow rate should be low. However, analyses of ozone and carbonyl compounds require a minimum flow rate. Standard methods for ozone measurement (~1.0 L min‐1) and carbonyl measurement (~ 0.6 L min‐1) suggest that the chamber should be operated at a minimum of 1.6 L min‐1. To ensure that samples included only chamber outlet air (and no incidental laboratory or dilution air), we 27
chose to operate the chamber at 2.0 L min‐1. This results in a chamber air exchange rate (12 h‐1) that is much higher than that in buildings, but is necessary for operation of the system. Measurement timing is sometimes important when studying the reactivity of building surfaces. The reactivity of some materials is stable and insensitive to time exposed to a reactant such as ozone. However, many materials “age” or change their reactivity over time. Ideally, a test method would be able to measure all parameters, instantaneously, for a very long period of time (even years) to ensure that the material has been thoroughly tested over the time frame of anticipated use. Of course, no test lab will have the resources to devote one or more chambers to a single material for years at a time. Furthermore, no manufacturer would be willing to wait that long. Therefore, a “reasonable” time frame should be chosen that coincides with the typical time frame for commercial test labs (up to one week). For the S&T preliminary chamber protocol, intended to be applied to many materials in “rapid” turn‐around mode, we chose 24 hours as a reasonable time period, but also collect a 2 hour set of samples. Some materials exhibit a significant aging effect over a 24 h period (Morrison and Nazaroff, 2002), which is consistent with qualitative aging phenomena observed in field studies (Wang and Morrison, 2006). The choice of ozone concentration delivered to the chamber, and present within the chamber, is a balance of providing a “realistic” concentration (typical of indoor environments), and challenging the material to ozone for what is certainly a very short period relative to its intended use (24 hours vs 10 years). Realistic indoor ozone concentrations range from zero (during night‐
time low ambient ozone periods) up to the upper decades, but almost always less than 100 ppb. However, subjecting the materials to higher ozone concentrations has several advantages: •
•
•
Higher inlet ozone concentrations result in a larger absolute difference between the inlet and out ozone concentrations. Up to a limit, this improves the sensitivity of ozone uptake parameter measurements (deposition velocity and reaction probability). The limit is the precision of the ozone monitor itself. A typical UV photometric ozone monitor is limited to ~1ppb at concentrations below 100 ppb, and 1% above 100 ppb. This suggests that the outlet concentration should be held at 100ppb or more (the inlet would naturally be higher). Higher ozone concentrations increase the rate of aging. This, theoretically, has the effect of stretching out the laboratory test period. For example, if the physical and chemical mechanisms of deposition and reaction are “first order” in nature, doubling the ozone concentration will double the rate of aging. Higher ozone concentrations result in higher rates of secondary emissions. This results in higher concentrations of carbonyl compounds which can improve secondary emission rate detection limits (i.e. secondary emission rates might be below detectable limits if the in‐chamber ozone concentration is to low). This also improves the measurement of yields. 28
Ideally, the ozone concentration within the chamber would be controlled at a precise value for consistency across all measurements, and inter‐lab consistency. Morrison and Nazaroff (2002) applied feed‐back control system to adjust the inlet ozone delivery rate such that the internal chamber concentration of ozone was 100 ppb throughout the experiment, regardless of the reactivity of the material or any aging phenomena. However, if ozone uptake and product yields are “first order”, the ozone concentration used will not influence measurement of deposition velocity or reaction probability. Including a feed‐back control system is more costly and more difficult to maintain. For these reasons, we designed our chamber for constant inlet concentration, a method more easily applied in commercial testing labs. 2.4.2
10 L S&T chamber and sampling protocol 2.4.2.1 Description of chamber system The S&T chamber exposure system is sketched in Figure 2‐5 and pictured in Figure 2‐6. The core of the system is a cylindrical 10 L electropolished stainless steel chamber (Eagle Stainless) that is top‐loading. The lid is penetrated with two ports (inlet and outlet) and seals to the chamber with a Viton gasket and three compression locks. The chamber is ventilated with a mixture of purified air, ozone and water (relative humidity). These parameters are controlled using mass flow controllers (MKS, inc), a water “bubbler” (Ace Glass) and an ozone generator. Compressed air is purified using an oil trap and an activated carbon (organic vapor specific) trap. The ozone generator was constructed in‐house, is fed pure oxygen and operates on the principal of arc‐
discharge formation of ozone from dry oxygen. At chamber exhaust, a pump draws exhaust air through sample tubes (controlled by mass flow controllers or meters), and an ozone analyzer (1008‐PC Dasibi) measures the ozone concentration. The ozone analyzer was calibrated, prior to the beginning of the project, using an ozone calibration source (model 306, 2B Technologies). A total of 8 electromechanical solenoid valves are used to control the direction of sample streams and to initiate and finish sampling. These valves allow for redirecting ozone to and from the main flow, and also direct the main flow to the chamber inlet or to a bypass. This allows both the inlet and outlet concentrations to be measured. All tubing is stainless steel with two short Teflon lengths after ozone generation and the water trap. The entire chamber system shown in Figure 2‐6 was situated within a walk‐in temperature controlled chamber, operated at 25 °C for the entire set of experiments except for temperature parameter variation experiments. Data was acquired and valves were controlled by an in‐house data acquisition system (LabView). 29
Mass Flow
Controller
Ozone Generator
Mass Flow
Meter
Solenoid Valves
Ozone Capacitor
(1 L)
Samples Tubes
(Tenax)
Chamber (10 L)
Metering Valve
High Purity Oxygen
Tank
Solenoid
Valve
Oil Trap
Ozone Traps
Mass Flow Controllers
Mass Flow
Controller
Material
Sample Tubes
(DNPH)
Activated Carbon
Trap
Bubbler
(1 L)
Water Trap
(1 L)
Pump
Ozone Analyzer
Exhaust
Air
Exhaust
Waste Gas
with
Activated Carbon
Figure 2‐5 Diagram of 10 L experimental chamber system at Missouri S&T Figure 2‐6 Image of 10 L chamber system. To the left are valves and mass flow meters that operate automatic DNPH and Tenax sample collection. To the right is the chamber with solenoid valves (i.e. bypass system) visible above the lid. 2.4.2.2 Chamber operation Before each experiment, the chamber was cleaned by rinsing with methanol, without touching the inner surface. The chamber was then exposed to >> 1000 ppb ozone for 2 h to quench reactive sites remaining on the chamber inner surface and then purged for 1 h with ozone free air. At this point, the material was installed on the bottom of the chamber, face up. During operation, three gas streams combined for a nominal total flow of 2.050 standard L min‐1, defined at 0 °C. At the 25 °C operating temperature of the system, the total actual flowrate was 2.238 L min‐1. The first stream was set to 1.0 L min‐1 and passed through a bubbler 30
to generate an air stream at ~100% relative humidity (RH). This stream was then mixed with the second 1.0 L min‐1 of dry air, for a combined stream with a relative humidity equal to 50%. These flows were adjusted for other relative humidity requirements. The relative humidity was checked once every two weeks using a hand‐held humidity sensor that was placed inside the chamber and allowed to come to equilibrium for one hour. A third stream of high purity oxygen was delivered through the ozone generator at 50 sccm. The ozone generator was operated to maintain the bypass concentration of ozone within a range of 150 to 200 ppb (except for parameter variation experiments). The main flow could be directed away from the chamber (to an activated carbon trap) during preparation or shut‐down periods to prevent over‐pressuring the chamber. During normal operation, the main flow was directed either to the chamber inlet through an solenoid stainless‐steel valve, or to bypass. Three solenoid valves were used to ensure that the flow did not re‐entrain into the chamber during bypass as shown in Figure 2‐5. The exhaust (or bypass) stream was continuously sampled by the ozone analyzer. The stream was periodically sampled by the DNPH and/or Tenax tube sampling train. The standard chamber test protocol, the timings of solenoid valve (bypass or to chamber) and sample valves are shown in Figure 2‐7. At time zero, the main flow was directed to the chamber. Initially, the material is exposed to ozone free gas for three hours. At 1 h, a two hour sample period was initiated for collection of “Primary Emission Rate (PES)” samples on two each of a DNPH and Tenax tube. Sample collection on one DNPH and one Tenax tube lasted for one hour, and was followed by another hour of replicate samples. The flowrates through the DNPH and Tenax sample tubes were set to 500 and 30 sccm, for a sample size of 30 L and 1.8 L respectively. The flow through the sample tubes was confirmed using a mass flow controller for the DNPH tubes (Aalborg USA) and a mass flow meter (Aalborg USA) combined with a needle valve for the TENAX tubes. At this time (3h), the ozone generator was activated and the main stream was directed to bypass the reactor. This allowed the ozone concentration to stabilize at the desired concentration. At this time (5 h) the main stream was directed to the chamber and the material inside the chamber was exposed to the ozone continuously until 17 h when the stream was bypassed for 0.5 h to measure the inlet ozone concentration. At 17:30, the stream was again directed to the chamber until 31h when the main stream was again bypassed for 0.5 h to check the bypass ozone concentration. At 7‐9 h and 29‐31 h, replicate DNPH and Tenax tube samples were collected that represent the 2 h and 24 h secondary emission rate samples. In summary, during a standard experimental protocol, the building material was exposed to flow, with or without ozone, for a total 28 hours. Exhaust ozone was measured continuously except for measurements of bypass ozone concentration at the beginning, middle and end of the experiment. Primary emission samples were measured in replicate before ozone was directed to the material. Two secondary emission samples were collected at 2 and 24 hours after initiation of ozone exposure. 31
2 Hr DNPH/Tenax
Samples
PES DNPH/Tenax
Samples
Samples
Elapsed Time (hours)
0
2
1
Chamber Conditions
·to chamber
·ozone off
3
5
7
bypass ozone
concentration
confirmation
B
A
B
A
24 Hr DNPH/Tenax
Samples
9
8
·to bypass ·to chamber
·ozone on ·ozone on
17
A
29
17:30
·to bypass ·to chamber
·ozone on ·ozone on
B
bypass ozone
concentration
confirmation
30 31
31:30
·to bypass ·system off
·ozone on
Figure 2‐7 Operational timing for ozone activation, bypass and sampling. 2.4.3
S&T measurement of ozone, ozone deposition velocity and reaction probability 2.4.3.1 Ozone concentration The ozone concentration was measured on bypass (inlet, Cin) and from the chamber (outlet or exhaust, Ce) with timing described in section 2.4.2.2. The following calculations were based on average concentrations at inlet (4‐5h, 17:15‐17:30h, 31:15‐31:30h) and exhaust (6‐7h, {16‐17 or 17:30‐18:30}h, 30‐31h), resulting in three values per experiment. Uncertainty in the ozone concentration is based on 2 times the standard deviation of the concentration measured over those periods (always higher than the instrumental uncertainty). 2.4.3.2 Deposition velocity To discern the deposition velocity due to the building material, the ozone removal characteristics of the chamber itself is necessary. To find the deposition velocity associated with the chamber walls, vd,w,, we apply equation 2‐1 to a chamber with a single ozone and redefine variables, Ce
=
C in
1
1
1 + v d , w Aw
Q
⇔ vd ,w =
⎞
⎜⎜
− 1⎟⎟ Aw ⎝ C e
⎠
λV ⎛ C in
2‐4
where V is the chamber volume, λ is the chamber air exchange rate (Q/V) and Aw is the inner surface area of the chamber. When the material is installed, it occludes a substantial fraction of the inner surface of the chamber and this must be accounted for when calculating the deposition velocity of the material itself, vd. vd =
λV ⎛ Cin
⎞
⎛A
⎞
⎜⎜
− 1⎟⎟ − vd , w ⎜ w − 1⎟
A ⎝ Ce
⎝ A
⎠ ⎠
2‐5
where A is the projected area of the sample material. 32
Uncertainties in deposition velocity were determined by propagation of errors of parameters in equations 2‐4 and 2‐5. Propagated uncertainty was due primarily to concentrations and area. 2.4.3.3 Reaction probability The measurement (calculation) of the reaction probability is based on the concepts outlined in section 2.1. The deposition velocity is a function of a “transport limited” deposition velocity, vt , and the reaction probability, γ. Rearranging elements of equation 2‐2, 4
γ =
vb
⎛ 1
1⎞
⎜⎜
− ⎟⎟
⎝ v d vt ⎠
−1
2‐6 The transport limited deposition velocity is determined by coating each material with a saturated KI solution (Morrison and Nazaroff, 2002) which, when dry, have been shown to be a near‐perfect sink for ozone. By subjecting this material to a standard (but shortened) chamber protocol, the deposition velocity that results is vt. Uncertainty is based on error propagation. 2.4.4
S&T primary and secondary emission rates, and product yield 2.4.4.1 Determination of C1­C5 aldehydes and acetone Gas samples for analysis of C1‐ C5 aldehydes and acetone were collected on glass tubes containing silica gel coated with dinitrophenylhydrazine (DNPH) (Aldrich/Supelco). Carbonyl compounds react with DNPH to form conjugate hydrazones which are more easily detected using UV spectroscopic methods. Gas was collected for 1 hour at 500 sccm. Tubes were broken to remove the silica gel and were extracted in 4 ml of acetonitrile. The solution was placed in a sonicator for 5 min to ensure complete extraction and then withdrawn and forced through a 0.45 µm syringe filter (EasyDisc) to remove any large solids that can clog the Waters High Performance Liquid Chromatograph (HPLC). The filtered solution was divided between a 1 mL HPLC sample vial, and a 7 mL storage vial. C1 thru C5 aldehydes and acetone were specifically quantified with this method. The HPLC method is based on EPA TO‐11A (U.S.E.P.A., 1999) and can be found in Appendix 6.2. This method was applied to all S&T and UT DNPH samples. Ozone traps (LpDNPH, Aldrich/Supelco) were placed upstream of the DNPH tubes to remove ozone and prevent reactions with carbonyls on the DNPH that can reduce recovery. (Refer to the ozone traps here and why they are used: reference (Calogirou et al., 1996; Clausen and Wolkoff, 1997; Kleindienst et al., 1998; Pellizzari and Demian, 1984). Ozone traps can accumulate carbonyls which contaminate later samples. They were cleaned after each experiment. The traps were placed inside a drying oven (60 °C), each purged with 40 sccm of pure nitrogen flow for 24 hours. This method was based on a method developed by UT (Poppendieck et al., 2007). 33
2.4.4.2 Determination of C6­C12 aldehydes Gas samples for the analysis of individual aldehydes from C6 through C12 were collected on TENAX‐TA thermal desorption tubes (Markes Intl.) at a target flow rate of 0.030 L min‐1 for one hour each. These were analyzed by thermal desorption (Markes, Intl.) into a gas chromotagraphy/ flame ionization detector (GC/FID) (Agilent), using cyclooctane as an internal standard. Internal standard was created using a Dynacalibrator. Cyclooctane was chosen as the internal standard because it is stable, separable from the target aldehydes, has a retention time similar to the target aldehydes and primary emission compound did not appear to interfere at that retention time. The internal standard is used to confirm that analysis was not compromised and also to normalize the peaks for consistency amongst samples. A sample of cyclooctane was placed inside a diffusion tube, the total mass of the diffusion tube and cyclooctane was then measured using a digital balance. The diffusion tube was then placed inside the heating chamber of the Dynacalibrator. The sample was allowed to equilibrate for more than a week before samples were taken for internal standard use. To take a sample for the internal standard the exhaust for the dynacalibrator was capped. The flow rate out of the sample tube was then tested via a digital mass flow meter, the flow was set to 80 sccm, to ensure enough of a sample was taken to be used as an internal standard. Applying a gas tight syringe to the end of the sample tube, a 10 mL sample was drawn over a 30 second time interval. This sample was injected over a 10 second period onto the Tenax tube while the tube was purged with a 0.040 L min‐1 stream of dry nitrogen. For GD/FID analysis, an aldehyde method was developed that is similar to that used by the EPA but was shortened to conserve both time and carrier gas. See Appendix 6.3 for details of the GC/FID conditions and method. To calibrate the thermal desorption tube method, we injected a sequence of increasing volumes of stock solutions of C6‐C12 aldehydes onto Tenax tubes and analyzed. Stock solutions were created for each of the seven upper aldehydes (C6‐C12) that were being quantified. Initial solutions of each of the individual pure solutions (Sigma‐Aldrich) were created using 25 ml vials, in each case 50 µl of the pure solution was added to 25 ml of methanol. From the initial stock solutions combined stock solutions with all seven aldehydes were created, four total combined stock solutions were created, with 10 µL and 5 µl being injected into 25 ml vials to create the new solutions. These resulted in a combined stock solution with an average concentration of 7.8 ng µl‐1 and a second solution with a concentration of 0.78 ng µl‐1. Volumes of 5 µl, 10 µl, 25 µl, 50 µl, 100 µl and 250 µl were injected to create a mass calibration curve up to 150 ng. After injection the tubes were placed in line with a nitrogen stream flowing at 40 sccm for 2 min, to purge methanol from the Tenax. After purging, the internal standard was added as described above. Once the calibration Tenax tubes had been prepared they were processed using the same TD/GC/FID method used to quantify the emissions and yields from the material samples. 34
A calibration curve was generated based on the known mass of aldehyde injected and the resulting peak areas, each of the calibration curves had R2 values of 0.98 or higher. Emission rates were determined based on the mass of each carbonyl collected. Analysis of laboratory blanks, inlet and empty chamber exhaust samples indicated that a background level of carbonyl compounds was present that was non‐insignificant relative to emission rates of some materials. Inlet air was found to be clean, but the chamber gasket appeared to be a low‐
level constant source for some of these compounds (not influenced by ozone). To account for background levels, primary emission rate for species k, ek,w, was calculated as follows ek ,w =
λV
As
(Ck ,e − Ck ,b )
2‐7 where Ck,e is the measured exhaust concentration of species k, and Ck,b is the background concentration of species k. The secondary emission rate, ek,s, (in the presence of ozone) was calculated as in equation 2‐7, while accounting for any chamber generated carbonyls (negligible). Molar yields were determined by dividing the molar secondary emission rates of each compound by the molar ozone flux to the material. yk =
ek ,w
C e vd
2‐8
2.4.4.3 Instrumental limit of detection Instrumental limit of detection was estimated using the lowest reproducible mass injected (multiplied by 3). This resulted in the following limits of detection (instrumental and gas concentration). 35
Table 2‐2. Instrumental limits of detection, LOD, for mass injected (ng) and resulting gas concentration (ppb) for DNPH (C1‐C5 aldehydes and acetone) and Tenax (C6‐C12 aldehydes) . C1 C2 C3 C4 C5 C6 C7 C8 C9 C10 C11 C12 acetone LOD (ng) 15.6 63.2 102.6 75.7 101.8 12.5 11.2 4.9 7.9 6.0 11.1 5.6 97.4 Instrumental LOD (ppb)
1.3 3.5 4.3 2.6 2.9 5.1 4.0 1.6 2.3 1.6 2.6 1.2 4.1 Analysis of laboratory blanks, inlet and empty chamber exhaust samples indicated that a background level of carbonyl compounds was present and could not be reduced further. 2.4.5
48 L UT chamber and protocol The UT 48 L chamber system has the same fundamental basis as the S&T chamber system, but provides for side‐by‐side testing of materials and an empty chamber. A key difference is that the air exchange rate for the UT chamber is 2 h‐1, near‐surface air velocities are lower and the transport limited deposition velocity is lower and may be closer to typical values for building surfaces than the S&T chamber. A diagram of the experimental system used to test materials in the UT laboratory is provided in Figure 2‐8. Three identical 48‐L electro‐polished stainless steel chambers (dimensions: 25 cm x 38 cm x 50 cm) were used in parallel. The chambers were cleaned with deionized water and a heat gun before the beginning of each experiment in order to remove particles and chemicals that could have deposited or adsorbed to chamber walls. 36
Figure 2‐8: Experimental system used to test materials for inter‐laboratory validation and for assessment of materials exposed in field sites. Room air was dehumidified by passing through a column containing 8 mesh Indicating Drierite (Drierite Company, USA) and cleaned by passing through an activated carbon filter. The air flow was then split into two paths, one of which was fed to a UV‐based ozone generator (modified zero air generator, Perma Pure LLC) to introduce ozone to the air stream (except during primary emissions assessment). A split stream of air was then passed through a bubbler to achieve a desired relative humidity (RH) before being introduced into the chambers. Relative humidity was measured at the inlet of the chambers using an RH probe (TSI, Inc., Q‐Trak 8551). Mass flow controllers (Aalborg, USA) were used to maintain a constant volumetric flow rate entering each chamber. The air entered and exhausted from the chamber through perforated stainless steel tubes extending across the interior length of each chamber. Sampling ports for ozone and by‐product measurements were placed on the inlet and outlets of the chambers. Laboratory tests were completed under the following experimental conditions: 50 ± 2 % RH, 147 ± 10 ppb inlet ozone concentration, two air exchanges per hour. This air exchange rate was chosen to provide enough air flow for sampling of by‐products and ozone (as described in section 2.4.1). The airflow rate through the chambers was measured using a bubble flow meter (Gilibrator 2, Gilian, Sensidyne, LP) to confirm the air exchange rate. The mean (± 1 37
standard deviation) steady‐state ozone concentration (across the entire experimental program) in chambers that contained materials ranged from 59 ± 9 ppb for carpet to 89 ± 8 ppb for painted gypsum wallboard. 2.4.6 UT measurement of ozone and ozone deposition velocity in 48 L chamber Ozone concentrations in the inlet and exhaust streams were measured using a single UV‐cell ozone monitor (model 202, 2B Technologies). The inlet ozone concentration was kept constant for the duration of the experiment. Tests were run for over two hours, allowing steady‐state ozone concentrations to be achieved in the chambers. The ozone monitor was recalibrated every three months during the experimental period. An ozone calibration source (model 306, 2B Technologies) was used. Four‐point calibration curves were used and resulted in R2 values above 0.99. Chamber tests were run for sufficient time that a steady‐state condition with respect to ozone concentration was reached in the chamber. For every other set of experiments, one of the three chambers was left empty to allow calculation of the deposition velocity of ozone to the chamber walls derived for a well‐mixed flow through chamber at steady‐state: 0 = λcin − λce − v d , w
Aw
Ce
V
⇔ vd ,w =
λV ⎛ C in
⎞
⎜⎜
− 1⎟⎟ Aw ⎝ C e
⎠
2‐9 where λ is the air exchange rate of the chamber (h‐1), V the volume of the chamber (m3), Aw is the total area of the chamber walls (m2), Cin is the inlet ozone concentration (ppb), ce is the ozone concentration in an empty chamber (ppb), vd,w is the ozone deposition velocity on the chamber walls (m h‐1). A steady‐state mass balance on a well‐mixed chamber containing a sample allows calculation of the deposition velocity of ozone on the material tested: 0 = λcin − λc − v d , w
A
Aw − As
c − vd s c ⇔
V
V
vd =
λV ⎛ C in
⎞
⎛A
⎞
⎜⎜
− 1⎟⎟ − v d , w ⎜ w − 1⎟ 2‐10 A ⎝ Ce
⎝ A
⎠
⎠
where As is the horizontal projected area of the material sample (m2), c is the ozone concentration in a chamber containing a material sample (ppb), vd is the ozone deposition velocity on the material sample (m h‐1) and all other variables are as previously described. Note that these equations are identical to those used to calculate deposition velocities in the 10L S&T chamber. 38
Uncertainties in the measured deposition velocities were calculated with an error propagation analysis using the maximum of instrument error, ±2% for the ozone analyzer, ±1% for the bubble flow meter and an error on area measurements that was estimated to be less than 10%. 2.4.7 UT primary and secondary emission rates, and product yield Heavy aldehydes (C5‐C10 n‐aldehydes, benzaldehyde, tolualdehyde) in chamber air were collected using Tenax®‐TA (Supelco, Inc. 80/100 mesh) adsorbent packed in glass liners (SISS, Open liners, tapered, frit, 3 mm I.D). Fiberglass wool was inserted on either side of the adsorbent throughout the experimental program. Prior to sampling the Tenax®‐TA tubes were conditioned at 330 ºC for 2 hours in a gas chromatograph oven (Hewlett‐Packard 5890) with a 200 mL min‐1 purge of ultra‐high purity nitrogen gas (Airgas, Inc). When not in use, Tenax®‐TA tubes were placed in stainless steel holders sealed with stainless steel Swagelok® unions, caps, and PTFE ferrules (Swagelok, Inc.). These assemblies were then placed in a hermetically sealed glass jar filled with a 5 cm depth of granular activated carbon to adsorb any contaminants in jar air. Sampling pumps (Model VSS‐1, A.P. Buck, Inc.) were used to draw inlet and outlet chamber air through adsorbent tubes. Low‐flow valves were utilized to achieve a target flow rate of 42 mL min‐1. Flow rates were set and verified for each pump prior to each experiment utilizing a bubble flow calibrator (Model Gilibrator 2, Gilian, Sensidyne, LP). Sample times of one hour were used throughout the experimental program. Light aldehydes (C1 – C5) were collected utilizing sampling pumps (Model VSS‐1, A.P. Buck, Inc.) to draw inlet and outlet chamber air through pre‐packed DNPH adsorbent tubes (SKC, Inc., P/N 226‐119). Prior to each experiment, a target flow rate of 400 mL min‐1 was set utilizing internal pump calibration settings. Flow rates were verified for each pump prior to each experiment utilizing a bubble flow calibrator (Model Gilibrator 2, Gilian, Sensidyne, LP). Ozone scrubbers (Supelco, LpDNPH ozone scrubbers, 505285) were used when sampling occurred on ozonated air to avoid interferences that might occur because of ozone reacting with sorbent materials. Ozone scrubbers were placed about 4 cm upstream of the sampling tube and attached via 0.3175 diameter PTFE tubing. Ozone scrubbers were cleaned between experiments according to a previously established method (Poppendieck et al., 2007). By‐products were sampled on the chambers before and after ozone injection. Primary emissions were measured after the materials had been in their chamber for 1.5 hours with non‐ozonated conditioned air introduced in the chambers. Secondary emissions were measured after the materials had been in their chamber for about 3 hours with ozonated conditioned air introduced into the chambers. Sampling events lasted one hour. One chamber in the system was left empty every other set of experiments to evaluate the by‐
product emission rates of chamber walls. The emission rate of the chamber walls for each compound was calculated using the following equation derived for a well‐mixed flow through chamber at steady‐state: 39
ek ,w =
λV
Aw
(C k ,e − C k ,in ) 2‐11 where Ck,in is the inlet concentration of compound k (μg.m‐3), Ck,e is the concentration of compound k in an empty chamber (μg.m‐3), ek,w is the area normalized emission rate of compound k from the chamber walls (μg.m‐2.h‐1) and all other variables are as previously described. Emissions from chamber walls were always negligible relative to those from materials. Emissions of each compound from test specimens were calculated based on a mass balance on a well‐mixed flow‐through chamber at steady‐state, accounting for emissions from chamber walls: ⎛
0 = λcin − λc + ew ( Aw − As ) + e s As
⇔ es =
λV (c − cin ) − λV (ce − cin )⎜⎜1 −
⎝
As
As ⎞
⎟
Aw ⎟⎠
2‐12 where ck is the concentration of compound k in a chamber containing a material sample (μg m‐3), ek,s is the emission rate of compound k from the material sample (μg m‐2 h‐1) and all other variables are as previously described. Uncertainties in the measured by‐product emission rates were calculated with an error propagation analysis using instrument error of ±1% for the bubble flow meters used to calibrate sampling pumps and measure the airflow rate through the chambers, ±10% for the GC/FID and an error on area measurements that was estimated to be less than 10%. Molar yield of reaction products was calculated as in equation 2‐8. 40
2.5 Task 2: Protocol Variations In the S&T 10L chamber, we evaluated the impact of conditions on the resulting deposition velocities and byproduct yields. Due to limited time and resources, we tested only two materials, carpet FC‐1 and clay plaster WCP‐1. The standard protocol was followed, changing only one parameter at a time: Temperature (15 to 31 C), relative humidity (25‐75%), ozone (40‐
>300 ppb). For the clay plaster, we also considered exposure time and tested the material after 7 days of exposure to ozone in the chamber. 41
2.6 Task 4: Materials preparation and testing in S&T 10 L chamber 2.6.1 General testing methods See section 2.4.2 for chamber test methods 2.6.2 General material preparation A hydrated solution of sodium silicate (NaSiO4) (Aldrich) was used to seal the back and edge of all of the samples prior to testing. Sodium silicate is considered to be unreactive with ozone. The sodium silicate was applied to the material using a piece of unreactive foam, a fresh piece for each sample. It was applied from a beaker containing initially 20 mL of sodium silicate, with additional added depending on the material. Ceiling tiles and several other porous materials needed more sodium silicate solution then other materials. The samples were then allowed to dry for 24 hours before being sealed in Teflon sheeting prior to testing. 2.6.3
Material specific preparation 2.6.3.1 Carpets FC­1 and FC­2, resilient flooring FRf­1 Materials were cut into nine inch diameter circles using scissors, cleaned with methanol prior to cutting. They were then prepared as described in 2.6.2. 2.6.3.2 FRf­2 Rubber puzzle­locking tile resilient flooring Using a standard wood keyhole saw nine inch diameter circles were cut from the raw rubber tiles. They were then prepared as described in 2.6.2. 2.6.3.3 FRf­3 Bio­based tiles, resilient flooring Due to the brittle nature of the Armstrong Floor Tile each tile was shaped, via scoring and snapping off the excess, into shapes that approximated the nine inch diameter circle. They were then prepared as described in 2.6.2. 2.6.3.4 FCf­1 Porcelain floor tile After appraisal it was determined that any attempt to shape these tiles (e.g. by cutting with a ceramic cut‐off saw) would result in contamination. We decided to test the tiles as is (they were small enough to fit directly into the reactor). This resulted in a smaller cross‐sectional area compared with the standard protocol. This was accounted for in the calculations. As with all other materials, they were prepared as described in 2.6.2. 2.6.3.5 FWf­1 and FWf­2 Renewable wood flooring The samples were cut using a standard wood keyhole saw (pre‐cleaned). Machine saws were not used because of the likelihood of contamination of the sample. The samples were cut into two trapezoidal pieces as a best fit to the nine inch diameter circle of a standard sample. The 42
difference in cross‐sectional area relative to standard sample shapes was accounted for in calculations. They were then prepared as described in 2.6.2. 2.6.3.6 WC­1 Cork wall tiles The manufacturer supplied Natural Cork Subfloor Primer was applied to the USG Drywall, which had been cut to nine inch diameter circles. After allowed to dry for 24 hours the manufacturer supplied adhesive was applied and cork wall tile, cut into nine inch diameter circles using pre‐
cleaned scissors, was then applied. They were then prepared as described in 2.6.2. 2.6.3.7 WC­2 Acoustical Wall Panels The acoustical wall panels had been constructed to our specifications (8.5” circles) and needed no further preparation other than that described in 2.6.2. 2.6.3.8 WC­3 Fabric wall covering WC‐3 wall fabric was cut into nine inch diameter circles using scissors pre‐cleaned with methanol. Using standard wallpaper paste, as recommended by the Xorel website instructions section, the wall fabric was adhered to standard USG drywall. The material was allowed to dry for 24 hours and then excess fabric and drywall were trimmed. The material had excess dust blown free with compressed air. Material samples were then prepared as described in 2.6.2. 2.6.3.9 WP­1 Latex paint and primer WP‐1 pre‐painted drywall sheets were received from the University of Texas. The primer and paint had been applied at UT, per manufacturer’s recommendations, three months before shipping. Nine inch diameter samples were cut from the drywall sheet using a standard keyhole wood saw, cleaned with Methanol prior to cutting. A box knife was then used to shape and clean the edges of the material to ensure proper fit within the test chamber. Clean compressed air was used to blow excess dust off the sample. 2.6.3.10 WP­2 Clay paint After calling Bio Shield customer service we decided to use a primer, despite the stated claim that primer is unnecessary. Bio Shield customer service recommended its use, to extend the life of a can of paint to paint more surface area, which most private consumers would, it is assumed, wish to do. No specific primer type or brand was recommended by Bio Shield and “Felspar” primer was chosen as acceptable. After the Felspar Primer was applied and allowed to dry for 24 hours, the Bio Shield paint was applied using a paint roller on two samples and paint brush on two samples, to approximate the type of texturing that would occur in a home. Material samples were then prepared as described in 2.6.2. 2.6.3.11 WP­3 Collagen paint USG (WD‐1) drywall samples were cut to 9” and prepared by painting Felspar primer using a roller. After 24 hours of drying, WP‐3 Collagen paint was also rolled onto the drywall circles. 43
These were allowed to dry for 24 more hours. Material samples were then prepared as described in 2.6.2. 2.6.3.12 WCP­1 Clay plaster on drywall The clay mixture was applied to WD‐1 drywall. The drywall pieces were first cut to 9” diameter circles using a keyhole saw. American Clay Textured Primer was then applied to the drywall and allowed to dry for 24 hours. After the primer had dried the WCP‐1 clay plaster was mixed according to the ratios prescribed by American Clay, but in small quantities due to the small size of the samples to test. The clay plaster was prepared by mixing 20 grams of pigment with 2000 grams of clay powder and 1 Liter of water. Using a clay mixing paddle and a five gallon bucket the clay, water and pigment was mixed together until a smooth consistency was obtained. The mixture was then applied to the drywall using a masonry spatula. Smoothing of the clay was performed as recommended by the online instructions and videos located on the American Clay website (XXX). Material samples were then prepared as described in 2.6.2. 2.6.3.13 WD­1, CP­1, CP­2, CP­3l Nine inch diameter circles were cut from the raw material, using a standard wood keyhole saw cleaned with methanol prior to cutting. Excess dust was blown off the sample with clean compressed air. Material samples were then prepared as described in 2.6.2. 44
2.7 Task 3a: Parallel lab validation The purpose of the validation was to compare the results derived using different sized chambers. The major anticipated difference will be the deposition velocity for highly reactive materials because larger UT chambers are expected to have lower a mean air velocityies over samples than the S&T chamber (air exchange rates 2 and 12 hr‐1, respectively). Low reactivity materials are expected to exhibit similar deposition velocities. Secondary emission rates are influenced by ozone deposition rates and the chamber ozone concentration, so these are anticipated to be different. However, within the limits of quantification, the byproduct yields should be the same. Three of the listed materials (Table 2‐1) were used in parallel lab validation experiments. CP‐2 (Eurostone ceiling tile), FC‐1 (Interface carpet) and WP‐1 (drywall painted with EcoSpec paint and primer). Each was measured in replicate in both UT and S&T chambers by their respective chamber methods. 45
2.8 Task 3b: Field exposure and aging of selected materials A field study was conducted to evaluate oxidation reactions between ozone and three building materials as well as fibrous activated carbon mat over a six‐month period. The activated carbon mat was added not as a green building material but rather as a comparison; activated carbon is highly reactive with ozone and does not produce substantial reaction products. Field samples were brought back to the laboratory to be tested every month allowing for determination of ozone deposition velocities. At the beginning, middle and end of the field study, primary and secondary emissions in the presence of ozone were determined for each material. 2.8.1 Materials In addition to fibrous activated carbon mat, three green building materials were used in the field study: CP‐2 (perlite ceiling tile), FC‐1 (recycled material carpet) and WP‐1 (drywall painted with EcoSpec paint and primer). 2.8.2 Field study A field study was completed to observe temporal variations in ozone removal efficiency and corresponding by‐product emissions following material exposures to real‐world (field) environments. Each material was tested for ozone deposition velocity, and primary and secondary emissions prior to placement in the field. Samples were then placed in real homes and commercial/institutional buildings located in Austin, Texas, for a six‐month period. Test materials were removed from the field on a monthly basis and brought back to the laboratory for ozone deposition velocity measurements. Primary and secondary emissions were also determined after three and six months. Following laboratory analysis the materials were returned to their initial field locations. Samples were transported in individual plastic bags that were changed every month. See section 2.4.5 for chamber protocols and section 2.4.6 and 2.4.7 for details on analytical procedures. 46
Table 2‐3: Field locations and characteristics # Building type Room type 1 Office building 2 Number of samples Ceiling Carpet GWB Office 1 2 1 House Kitchen 2 1 1 3 House Home Office 1 1 2 4 House Bedroom 1 1 1 5 Unoccupied Test House Living room 1 1 1 At each field site, samples of activated carbon, ceiling tile and painted gypsum wallboard were mounted on metal wire stands and set on shelves approximately 1.8 m from the floor. Samples of carpet were placed on the floor in relatively protected areas to avoid having occupants repeatedly stepping on them during the field test. The backside and edges of samples were covered with aluminium foil to avoid contact of these surfaces with the environment. This protection was also used during laboratory experiments to avoid measuring the characteristics of surfaces that are not usually exposed in the indoor environment. Indoor environmental conditions were monitored at each test location so that their effect on material properties could be analyzed. Continuous temperature and relative humidity (RH) measurements were taken using a HOBO U12‐013 (Onset Corporation, USA). As a gross measure of dustiness near the material, dust samples were taken monthly using adhesive Scotch Magic tape (3M, USA) in the vicinity of the samples before they were brought back to the laboratory and analyzed by a microscope (BX40, Olympus, USA) with image processing software (Image J) to measure the percent area of the samples covered by dust. Finally, the total organic gaseous content of the air was measured using passive samplers made of a large volume glass liner (SISS, Open liners, tapered, frit, 3 mm I.D.) for the injection port of a gas chromatograph (GC). The sampler was packed with Tenax‐TA (Supelco Inc., 80/100 mesh) and placed at each field site. The samples were then analyzed following methods described in Section X. See Figure 1 for a description of the passive sampler. Figure 2‐9. Organic gaseous compounds passive sampler 47
2.9 Task 5: Large chamber assessment of materials To simulate the conditions in a “real” indoor environment, experiments were conducted in a large room‐sized (68 m3) chamber to evaluate ozone removal to three green building materials. Primary emissions were determined for each material in the absence of ozone. Ozone deposition velocities and secondary emissions were then determined by exposing individual materials to ozone. 2.9.1
Environmental Chamber Experiments were completed in a 68 m3 climate‐controlled stainless steel environmental chamber (Figure 1). Tests were first completed in the absence of materials (background experiments) and then with each individual material mounted in the chamber. Mixing intensity in the chamber was varied using a floor mixing fan calibrated to two flow rates: 400 m3 hr‐1 and 800 m3 hr‐1, (6 hr‐1 (low) and 12 hr‐1(high) equivalent recirculation rates, respectively. Mixing fan speed was controlled via a single‐phase Variac transformer (Model TDGC‐0.5KM, ISE, Inc.) to allow variable AC voltage input to the fan. Fans were oriented such that air flow was parallel to materials. Relative humidity was varied (25%, 50% and 75%) with temperature held constant throughout experiments at 25 ºC by a heating and air conditioning unit and a proportional, integral, derivative controller (Allen‐Bradley, Inc.). Experiments completed for the background and three test materials are summarized in Table 1. Outdoor air was continually introduced into the chamber at a controlled air exchange rate of approximately 1 hr‐1 for the duration of the experimental program. Prior to entering the chamber, outdoor air was filtered in the chamber inlet duct using a 0.5 cm thick activated carbon cloth placed between two HEPA filters. 48
Figure 2‐10. Schematic of large environmental chamber for materials testing. 49
Table 2‐4. Summary of experimental conditions. Test Material
Relative
Humidity
(%)
25
Background
50
75
25
Carpet
50
75
25
Ceiling Tile
50
75
25
Drywall
50
75
Mixing
Condition
ACH
(hr-1)
Low
High
Low
High
Low
1.02
1.02
1.13
1.07
1.02
High
Low
High
Low
High
Low
1.04
1.10
1.13
1.09
1.20
1.08
High
Low
High
Low
High
Low
1.10
1.01
1.15
1.15
1.20
1.45
High
Low
High
Low
High
Low
1.16
1.01
1.04
1.06
1.08
1.04
High
1.01
Low and High refer to 6 hr‐1 and 12 hr‐1 of room mixing, respectively. Prior to the start of experiments the chamber was cleaned with low‐VOC glass cleaner. Before beginning experiments for each material, the chamber was purged at an elevated air exchange rate (~4 hr‐1) for two days, and passivated with elevated ozone levels (~500 ppb) for 2 hours. This cleaning protocol was repeated following the removal of a material from the environmental chamber. 50
2.9.2 Materials Recycled carpet (FC‐1) was the first material tested. It was installed by placing 25.4 m2 of carpet atop the raised floor shown in Figure 2‐10. After testing under conditions described in 2.9.1, the carpet was removed from the chamber and 22.5 m2 of perlite ceiling tile (CP‐2) was installed on the chamber’s suspended ceiling. Finally, the ceiling tile was replaced by painted drywall (WP‐1) with a coverage area of 14.9 m2. The drywall had been painted 3 months before experiments were performed. 2.9.3
Ozone Generation and Injection Ozone was injected into the chamber through 6 m of 0.635 cm OD PTFE tubing connected to a port on the inlet duct downstream of the inlet ozone analyzer. Ozone was generated by of a modified NOx analyzer (Model 10 NO‐NO2‐NOx analyzer, Thermo Electron Corporation) fed by pure oxygen (Airgas, Inc.). For each experiment, ozone was injected until the chamber concentration reached approximately 140 ppb. Ozone injection was then terminated and the resulting ozone concentration decay was measured. 2.9.4
Ozone Measurement Ozone concentrations were measured downstream of the inlet filter assembly via an ultraviolet absorbance ozone analyzer (Model 202, 2B Technologies, Inc.). The ozone analyzer was connected to a sample port via 4 m of 0.635 cm outer diameter (OD) PTFE tubing. Outlet ozone was measured via an ultraviolet absorbance ozone analyzer (Model 205, 2B Technologies Inc.) connected to a sample port on the outlet duct of the chamber via 5 meters of 0.635 cm OD PTFE tubing. Ozone monitors were calibrated using an Ozone Calibration Source (Model 306, 2B Technologies, Inc.) prior to the experimental program and re‐checked for consistency every three weeks. Ozone monitors were calibrated utilizing a five‐point calibration curve with resulting R2 values of greater than 0.99. 2.9.5
By‐Product Sampling For each experiment duplicate heavy and light aldehyde samples were collected on the chamber outlet. One sample per day was collected on the chamber inlet. Details of sampling are found in Section 2.4.7. By‐product sampling began when the chamber ozone concentrations decayed to 90 ppb. Due to the high initial ozone concentrations, LpDNPH ozone scrubbers (P/N 505285, Sigma‐
Aldrich, Inc.) were installed 1 cm upstream of each sampling tube. This assembly was connected to the sample pumps via 15 cm of 0.635 cm diameter OD PTFE tubing. Approximately 10 cm of 0.3175 cm diameter OD PTFE tubing was used upstream of the ozone scrubber to draw air samples from the center of the inlet and outlet ducts. Scrubbers were cleaned prior to each experimental run following previously established protocols (Poppendieck et al. 2007). 51
Sample break‐through tests for light aldehydes were conducted utilizing a 100 L Tedlar bag (SKC, Inc.) containing chemicals of interest at near experimental concentrations. Air was sampled from the bag following experimental sampling protocols, but with two adsorbent tubes placed in series. Less than 1% of expected mass was found on the breakthrough tube for all chemicals of interest, indicating a safe pump rate and volume. 2.9.6
By‐Product Analysis Details of analytical procedures are found in Section 2.4.5. A minimum of one blank Tenax®‐TA tube was analyzed each day that experiments were completed. To ensure consistent GC/FID performance, a minimum of one standard of each chemical of interest at a given concentration was analyzed each day experiments were completed. On average, GC‐FID responses from standards fell within ±5% of the expected mass. Method detection limits (MDLs) were determined in accordance with EPA method TO‐17 (EPA 1999). Calculated MDLs ranged from 0.09 µg m‐3 for heptanal to 0.5 µg m‐3 for decanal. Quality assurance protocols and results are provided in Appendix LC3. Light aldehyde samples and one lab blank per experiment were wrapped in aluminum foil, bagged, packed with ice and shipped to Missouri University of Science and Technology for analysis within 30 days of a given experiment. Prior to shipping, samples were stored in a laboratory refrigerator at approximately 4 degrees C. These samples were analyzed utilizing HPLC‐UV following previously defined protocols. 2.9.7
Data Analysis 2.9.7.1 Ozone deposition velocities Ozone deposition velocities were calculated for chamber surfaces (background) and test materials based on a mass balance on the environmental chamber. Anemometer measurements indicated that the chamber was generally well‐mixed at both high and low mixing intensities. Equation 2‐13 describes the ozone concentration as a function of time in the well‐mixed chamber: A
A
dC
= λCo − λC − vd C − vd ,SS SS C
V
V
dt
Where: Co = ozone concentration entering the chamber, ppb C = ozone concentration inside the chamber, ppb λ = air exchange rate, hr‐1 vd= deposition velocity to material, m hr‐1 A = material area, m2 V = chamber volume, m3 52
2‐13
vd,SS= deposition velocity to stainless steel chamber walls, m hr‐1 ASS = exposed surface area of chamber walls, m2 Equation 1 was solved in discrete form for the time‐variant deposition velocity as described by Poppendieck et al. (2007). Heterogeneous reactions are typically modeled via resistance uptake theory. (Cano‐Ruiz et al. 1993). This theory relates the previously described deposition velocity to a series of resistances (Equation 2‐14). 1
1
4
= +
v d vt
V γ
(1)
(2)
(3) 2‐14
Where: vt = transport limited deposition velocity, m h‐1 γ = reaction probability, dimensionless <V> = Boltzmann’s velocity, m h‐1 Term 1 represents the overall resistance to deposition. The overall resistance is the sum of two resistances, the transport resistance (Term 2) and reaction resistance (Term 3). Ozone was injected into the chamber in the absence of test materials for all environmental conditions to determine background ozone deposition velocity. This value was utilized in determining the ozone removal to test materials by subtracting the background deposition velocity for a particular environmental condition from the deposition velocity with test materials present for that same environmental condition. Background removal to chamber walls was corrected when calculating deposition velocity to materials by reducing the background ozone removal according to the fraction of chamber surfaces covered by the material. Error bars for each ozone measurement experiment represent the larger of instrument error or standard error of the ozone decay regression. Instrument error was calculated by summing in quadrature the uncertainties associated with the air exchange measurement (5% of the measured flow rate) and the ozone monitor (2% of the measured ozone concentration). Standard error was calculated for the decay period for which ozone deposition velocity was calculated (140 ppb – 40 ppb). 2.9.7.2 By­product emission rates By‐products emission rates were calculated utilizing average by‐product concentrations over the sampling period following methods outlined by Morrison and Nazaroff et al. (2002). Emissions are reported in terms of a mass emission rate normalized by the horizontally projected surface area of the test material. The following equation is determined from a mass balance on the chamber: 53
E an =
(1)
QCan V dC
+
A
A dt
(2)
(3) 2‐15
Where: Ean = area normalized emission rate for an analyte, µg m‐2 hr‐1 Can = average analyte concentration inside the chamber, µg m‐3 A = test material horizontally projected surface area, m2 Q = flow rate through environmental chamber, m3 hr‐1 Can was determined by calculating sample concentrations based upon the ratio of the mass collected on the sample tube to the volume of air pumped through the tube. Because of the limited number of by‐product samples collected during the experimental period it was not possible to accurately determine the rate of change of concentration with respect to time in term (3). As such, steady state conditions were assumed (term 3 was neglected). This assumption is equivalent to assuming that the positive and negative derivative terms cancel over the experimental sampling period. Emission rates calculated in this manner are suitable for comparison of materials but not for absolute emission factors. Background primary emission rates were calculated by subtracting blank masses of each analyte of interest from analyte masses collected during background experiments: E P , BG
⎛ m − mb
Q P , BG ⎜⎜ an
⎝ Vc
=
ASS
⎞
⎟⎟
⎠
2‐16
Where: EP,BG = background area normalized primary emission rate, µg m‐2 hr‐1 QP,BG = flow rate through environmental chamber for primary emission background experiment, m3 hr‐1 man = mass of primary background analyte collected, µg mb = mass of analyte on blank tube, µg Vc = sample volume collected, m3 Background secondary emission rates were calculated by subtracting analyte emissions from the chamber in the absence of ozone from analyte emissions from the chamber in the presence of ozone: 54
E S , BG
⎛m
Q P ,BG ⎜⎜ an
Q S , BG (C an , S , BG )
⎝ Vc
=
−
ASS
ASS
⎞
⎟⎟
⎠
2‐17
Where: ES,BG = area normalized secondary emission rate for background, µg m‐2 hr‐1 Qs,BG = flow rate through environmental chamber for secondary emission background experiment, m3 hr‐1 Can,S,BG = concentration of analyte collected for background experiment following ozonation, µg m‐3 All other parameters are as previously described. Primary analyte emission rates were calculated by subtracting the background analyte emission rates from the emission rates for a specific material experiment in the absence of ozone: EP =
QP (C an, P )
A
⎛ ASS − A
− E P , BG ⎜⎜
⎝ ASS
⎞
⎟
⎟
⎠ 2‐18
Where: EP = area normalized primary emission rate, µg m‐2 hr‐1 QP = flow rate through environmental chamber for primary emission experiment, m3 hr‐1 Can,P = concentration of analyte collected for primary emission experiment, µg m‐3 All other parameters as previously described. Note that background analyte concentrations were corrected for the fractional coverage of chamber surfaces by the test materials. Secondary analyte emission rates were calculated by subtracting the sum of the primary emission rates and the secondary emission background rates from the emission rates measured following ozonation: ES =
QS (C an ,S ) QP (C an, P )
⎛ ASS − A
−
− (E S , BG )⎜⎜
A
A
⎝ ASS
⎞
⎟
⎟
⎠ 2‐19
Where: ES = area normalized secondary emission rate, µg m‐2 hr‐1 QS = flow rate through environmental chamber for secondary emission experiment, m3 hr‐1 Can,S = concentration of analyte collected for secondary emission experiment, µg m‐3 55
All other parameters as previously described. Equations 2‐16 – 2‐19 were each corrected for inlet analyte concentration by subtraction of the inlet concentration. Uncertainties in emissions were calculated by summing the individual uncertainties associated with the flow, concentration and area measurements in quadrature. The uncertainty associated with the concentration measurement was determined by summing the uncertainty associated with the mass measurement from the GC‐FID (heavy aldehydes) or HPLC‐UV (light aldehydes) and the uncertainty associated with the volume of chamber air pumped in quadrature. 2.9.7.3 Molar Yields The molar yield of each analyte was calculated by completing a mass balance on the analyte in the chamber: dCan
A
= λCan,o − λCan + γ an vd C
dt
V 2‐20
Where: γan = molar yield of analyte, (moles analyte/moles ozone) Can,o= outdoor concentration of analyte, ppb ‘Can= chamber concentration of analyte, ppb C = concentration of ozone in chamber, ppb Molar yield is defined as the moles of analyte formed due to material surface reactions with ozone divided by the moles of ozone removed from the air to the material’s surfaces. By this definition, a material that removes high amounts of ozone and emits low amounts of analyte has a lower molar yield than a material that removes less ozone and emits more analyte. The molar yields of each material presented herein are the yields above background. Equation 2‐20 was solved in discrete form during each ozone decay experiment for the molar yield of each analyte, and for the total yield of all heavy aldehydes. The discretized form of Equation 8, rearranged into an expression for
, the analyte concentration in the chamber at time t + Δt in units of parts per billion, is presented as Equation 9. Where: Δt = time step, hours = chamber concentration of analyte at time t, ppb 56
2‐21 = ozone decay rate, hr‐1 = chamber concentration of ozone at time t + Δt, ppb = chamber concentration of ozone at time t, ppb , γan, and were assumed constant at all times during each experiment, with the outdoor analyte concentration being negligible. Using the measured ozone concentrations at the inlet and outlet, and calculated ozone decay rates, Equation 2‐21 was solved from the start of ozone injection until the end of the sampling period. However, molar yields were determined only from the iterations within the one‐hour sampling period, with the assumption that the sampled analyte concentrations at the chamber outlet represented average concentrations in the chamber during the sampling period. By averaging all during the sampling hour, and then using an iterative solver to set the average equal to a sample analyte concentration, the molar yield was obtained. The total molar yield of aldehydes for each experiment was calculated by summing these individual yields. 57
2.10 Task 7: Field house measurements Experiments were conducted to evaluate ozone removal to perlite‐based ceiling tile (CP‐2) in the University of Texas Test House (UTest House). Aldehyde (C1 – C10) and acetone concentrations were measured in the presence and absence of CP‐2 to determine the effect of this material on indoor concentrations of aldehydes. 2.10.1 Test House – Small Bedroom Experiments were completed in an empty bedroom in the UTest House (Figure 2‐11). The bedroom had a volume of 34.5 m3, with a floor area of 11 m2 and total surface area (floor, ceiling, walls) of 63 m2. Surfaces present in the bedroom were painted drywall walls (54.6% of total surface area), textured plaster ceiling (17.7%), vinyl flooring (16%), two painted wood doors (4.2%), painted wood molding and window frame (3.1%) and a glass window (2.1%) with fabric curtains (2.1%) Mixing intensity in the room was varied using a commercially available standalone multi‐
directional fan. Experiments were completed with no fan input and with the fan set to the medium setting. Air speeds were measured using hot wire anemometers placed in the center of the room, at 1.5 m and 2.2 m above the floor. Air exchange rate (AER) was controlled by sealing a fan (Duct Blaster, The Energy Conservatory) assembled to 5 feet of 10‐in diameter flexible duct in the window of the bedroom. Outdoor air was introduced to the bedroom at a target air exchange rate (AER) of between 1 – 1.5 hr‐1. The AER was controlled by setting the Duct Blaster fan speed prior to each experiment utilizing a pressure and flow gauge (Energy Diagnostics Model DG‐700). All HVAC vents to the room were sealed with HVAC vent tape (Duct Mask, The Energy Conservatory). Door gaps were sealed utilizing foam insulation and fabric. Temperature and relative humidity were measured and recorded (HOBO U10, Onset, Inc.) during each experiment. Table 2‐5 summarizes the experiments completed for both the background and perlite ceiling tile conditions. 58
sealed ceiling vent
exhaust
sealed floor vent
CO2 injection
point at fan
outdoor ozone
sample point
intake
(100% outdoor air)
indoor
ozone, CO2, by-products,
temperature, & RH sample point;
ozone
injection point
Figure 2‐11. Diagram of bedroom in UTest House that was used for experiments. 59
Table 2‐5. Description of experimental parameters. Test Material
Background
Ceiling Tile
Fan
b
a
Condition
Off
Off
Off
Off
On
On
On
On
Off
Off
Off
Off
On
On
On
On
-1
Method
AER (hr )
SS-Day 1
SS-Day 2
SS-Day 3
Decay
SS-Day 1
SS-Day 2
SS-Day 3
Decay
SS-Day 1
SS-Day 2
SS-Day 3
Decay
SS-Day 1
SS-Day 2
SS-Day 3
Decay
1.52
1.08
1.33
1.01
1.15
1.30
1.53
1.51
1.36
1.45
1.30
1.15
1.33
2.02
1.29
1.46
Temperature
Relative
(◦C)
Humidity (%)
30.0
28.7
29.5
30.1
29.6
29.1
27.2
23.2
26.8
28.7
25.2
26.0
25.8
29.4
19.6
28.0
53
47
48
48
57
58
59
54
61
61
43
60
56
61
64
67
a.
Fan on medium setting. Air speed for fan off varied from 0.04 to 0.06 cm/s. Air speed for fan on varied from 0.18 to 1.41 cm/s. b. Days 1, 2, and 3 at steady‐state (SS) ambient ozone concentration. Ozone injection and decay on Day 4. The bedroom was thoroughly swept and vacuumed prior to the start of the experimental sequence. Walls were cleaned with a low‐VOC surface cleaner, purged at an elevated air exchange rate (~4 hr‐1) for two days, and passivated with elevated ozone (~500 ppb) for 2 hours. This cleaning protocol was repeated following the completion of background experiments and placement of ceiling tiles in the chamber. 2.10.2 Ozone Measurements Inlet ozone concentration was measured downstream of the Duct Blaster fan via an ultraviolet absorbance ozone analyzer (Model 202, 2B Technologies, Inc.). The ozone analyzer was 60
connected to a sample port in the fan housing via 6 m of 0.635 cm outer diameter (OD) PTFE tubing. Ozone concentration was measured in the center of the room, 1.8 m above the floor via a second ultraviolet absorbance ozone analyzer (Model 205, 2B Technologies Inc.) connected to the sample location via 5 meters of 0.635 cm OD PTFE tubing. Decay experiments were conducted by injecting ozone into the chamber through 4 m of 0.635 cm OD PTFE tubing from an ozone generator (Yanco, Inc.) fed by pure oxygen (Airgas, Inc.). Ozone was injected until the room concentration reached approximately 140 ppb, at which time the injection was terminated and ozone decay subsequently measured. Ozone monitors were calibrated using an Ozone Calibration Source (Model 306, 2B Technologies, Inc.) prior to the experimental program. Ozone monitors were calibrated utilizing a five point calibration curve with resulting R2 values of greater than 0.99. 2.10.3 By‐Product Sampling By products were sampled utilizing materials and protocols described in Section 2.4.7. The number and placement of sample tubes for these experiments were as follows: for each steady‐
state experiment (SS‐1 through SS‐3), samples inside the bedroom were collected on duplicate Tenax® tubes and duplicate DNPH tubes for heavy and light aldehydes, respectively. Simultaneously, duplicate samples on Tenax® tubes and DNPH tubes were taken outside the UTest House near the Duct Blaster intake. 2.10.4 By‐Product Analysis By‐product sampling and analysis protocols (both Tenax®‐TA and DNPH) were similar to those used for large chamber experiments as described in Sections 2.9.5 and 2.9.6. 2.10.5 Data Analysis 2.10.5.1 Ozone Ozone deposition velocities were calculated for existing room surfaces (background) and ceiling tile based on a mass balance on the test house bedroom. Equation 2‐22 describes the ozone concentration as a function of time in the well‐mixed bedroom: A
dC
A
= λCo − λC − vd C − vd , BG BG C
dt
V
V
Where: Co = ozone concentration entering the room from outside, ppb 61
2‐22
C = ozone concentration inside the room, ppb λ = air exchange rate, hr‐1 vd= deposition velocity to ceiling tile, m hr‐1 A = ceiling tile area, m2 V = room volume, m3 vd,BG= deposition velocity to background room surfaces, m hr‐1 ABG = background room surface area, m2 The bedroom was assumed to reach a new steady‐state instantaneously with a change in incoming ozone, validated by the agreement between steady‐state and transient ozone removal measurements. In this case, the left hand side of equation 2‐22 becomes zero, and the equation can be solved for vd. Following calculation of ozone removal in the room, transient experiments were conducted to validate assumptions made during steady‐state experiments. Protocols for this analysis follow those outlined in Section 2.9.7 (large chamber experiments). 2.10.5.2 By­Products By‐product emission rates were calculated following the same method that was used to determine emission rates in the large chamber (Section 2.9.7). However, small bedroom emissions are reported as whole‐room emissions so that emissions reported for ceiling tile reflect emissions from all materials exposed in the room, including ceiling tile. As such, emission rates for this series of experiments are not normalized by the horizontally‐projected surface area of material, as was the method for the large chamber analysis in Section 2.9.7; the effective surface area in the room remained unchanged after ceiling tiles were installed. Additionally, instead of reporting primary and secondary emission rates for each experiment, emission rates are reported for steady‐state ozone conditions (SS1 and SS3) and for non‐steady state conditions (Decay, Day 4) in the bedroom. The whole‐room emission rate is calculated from a mass balance on the assumed well‐mixed bedroom: E an = QC an + V
(1)
dC
dC
= λVC an + V
dt
dt
( 2)
(3) Where: Ean = emission rate of analyte, µg h‐1 Can = average analyte concentration inside bedroom, µg m‐3 62
2‐23
Q = flow rate through bedroom, m3 h‐1 λ = air exchange rate in bedroom, h‐1 As with the large chamber analysis, steady‐state conditions for analyte concentration were assumed such that Term 3 in Equation 2‐23 was neglected, and therefore emission rates were determined from the measured air exchange rates, the average analyte concentrations in the room above outdoor concentrations, and the volume of the bedroom. Emission rates for all steady‐ and non‐steady‐state ozone experiments in the bedroom were calculated by subtracting blank masses of each analyte of interest from the analyte masses sampled in the bedroom, as described by Equation 2‐24: ⎛ m − mb
E an = λVr ⎜⎜ an
⎝ Vc
⎞
⎟⎟
⎠ 2‐24
Where: Vr = volume of bedroom, m3 man = mass analyte collected in bedroom (above outdoors), µg mb = mass of analyte on blank tube, µg Vc = sample volume collected, m3 Errors associated with each by‐product measurement are presented herein. Uncertainties for emissions were calculated by summing the individual uncertainties associated with the air exchange rate, concentration, and volume measurements in quadrature. The uncertainty associated with the concentration measurement was determined by summing the uncertainty associated with the mass measurement from the GC‐FID (heavy aldehydes) or HPLC‐UV (light aldehydes) and the uncertainty associated with the volume of bedroom or outdoor air pumped in quadrature. 2.10.5.3 Molar Yields Molar yields were calculated by the method described in section 2.9.7. 63
2.11 Task 6: Grade development As noted in the introductory material, the grading system proposed here is intended to be more comprehensive than those that deal only with primary emissions. The new system should consider speciated primary emissions alongside secondary emissions, ozone removal capacity and the time scales over which these phenomena occur. Grading system (MS&T and UT). The test protocol will also include a grading system that will allow ease in comparison of materials. In 2006, Morrison and Corsi proposed a method to compare/rank building materials for their ozone removal capability and formaldehyde generation rates (Morrison et al., 2006). The grading system proposed here is more comprehensive and will consider speciated primary emissions, secondary emissions, and ozone removal capacity, as well as the time scales over which these phenomena occur. Possible examples of this kind of grading system and a preliminary assessment of materials are discussed here. Ozone removal grade: Rather than report the reaction probability, an unfamiliar parameter, the ozone removal capability should be based on the anticipated use of the material in a building. The “clean air delivery rate” (CADR) is a familiar standard used to grade the effectiveness of air cleaners. The same idea can be applied to building materials. For example, for a defined installed area of the material, A (e.g. 16 m2 for carpet in a residential room), the ozone removal rate (in m3 h‐1, ft3 min‐1 or cfm) can be described by Term 1 in equation (1). Using measured input values, (Morrison and Nazaroff, 2002) the CADR for ozone removal is 15 cfm (also equivalent to an activated carbon filtration rate of 15 cfm). For an entire residence (carpeted area = 2000 ft2) CADR =190 cfm (325 m3 h‐1). Replacing walls and ceilings with unpainted drywall (Poppendieck et al., 2007) results in a CADR of 6700 cfm for a commercial building with floor area of 20,000 ft2. Naturally ventilated buildings, which may not be able to meet strict ASHRAE 62.1 requirements for ozone filtration, may instead meet the spirit of the requirement through a sufficiently high CADR. Other grading scales will be considered, such as CADR normalized by presented area of the material (m3 m‐2). Reaction product grade: In many test protocols, the total VOC emission rate is reported. This measurement is only partially useful since individual chemical species are not taken into account. Individual chemical compounds emitted by building materials can be toxic, odorous or irritating at emission rates far below existing TVOC emission rate limits. Progressive methods speciate target compounds associated with particular products (e.g. Green label speciates for styrene, a carcinogen used in the manufacture of carpet), or identify a broad range of species (e.g. California’s Department of Public Health Standard Practice for testing VOC emissions from various sources using small‐scale environmental chambers, 2004). Thus, progress has been made in developing methods to identify acceptable materials based on primary emissions. However, 64
secondary emissions, due to chemical transformations that occur after installation, are not yet evaluated by any commercial testing lab. Secondary emissions are particularly problematic for installed acceptability of green materials. Bio‐based materials, such as linoleum, are often composed of unsaturated oils that are susceptible to auto‐oxidation and ozone oxidation. Several possible metrics for grading materials based on secondary emissions are possible. The anticipated approach, as in the ozone grade, could be to consider predicted product concentrations. If the predicted concentration is higher than a specified threshold, the product fails. Philosophically, the broad goal is to reduce pollutant concentrations overall. Therefore, a simpler metric might be to set a threshold on product yield, such as 0.05. In this case, only a small fraction of ozone consumed is converted to products. A single metric that combines ozone uptake and secondary emissions could also be envisioned. For example, products pass if they 1) meet existing primary emissions rate standards, 2) have an ozone removal rate of 0.1 cfm per square foot of floor area and 3) have a by‐product molar yield less than 0.05. 2.11.1 Primary emissions Primary emission rate test methods and standards for speciated emissions have been developed by several organizations and are presently used by the USGBC in their LEED system. These methods and standards are under constant scrutiny by several organizations (e.g. NIST, ANSI, USGBC, and others) and we do not believe it is particularly fruitful to attempt to improve on this process in this report. However, the determination of secondary emissions depends on a good accounting of primary carbonyl (or other ORP species) emissions. Therefore, we necessarily include the measurement of primary emissions as part of the overall measurement of ORP emission rates or yields. Further, we will point out that primary emissions include reactive terpenes and other molecules that contribute to overall “reactive pollution” in buildings. Of particular concern may be natural wood products that are not sealed. Pine, oak and other timber materials release a variety of terpenes and terpenoid compounds that can react with ozone and other oxidants in buildings. This chemistry produces irritants and aerosols with known and suspected adverse health effects. While elaboration is not within the scope of this project report, we suggest that future consideration of speciated primary emission standards include a reactivity scale factor, not unlike the characterization of outdoor atmospheric pollutant reactivity. Instead, the existing primary emission standards should continue to be applied (and improved) independently of the recommended ozone uptake and secondary emission rate standards. 2.11.2 Ozone removal potential Ozone removal potential can be graded in a number of ways (as noted in the introduction). During the project, we evaluated the following possibilities and their practical value as metrics for developing standards: ‐
Impact on specific building (combination of materials and other building characteristics) 65
‐
o Decay rate o CADR o Ozone concentration target o Ozone ratio target Individual materials o Reaction probability o Deposition velocity o CADR Results of this analysis and application of specific metrics to materials in this project are found in section.3.9. 66
3 Project results and discussion 3.1 Task 1: Preliminary chamber protocol reproducibility 3.1.1 S&T 10 L chamber Reproducibility was established for several materials early in the project. However, since every material was evaluated at least twice, we provide results associated with all 19 materials tested. Individual experimental results for deposition velocity and reaction probability are shown in Figure 3‐1 and Figure 3‐3. Discussion of the averages and their relationships to one another will be presented and discussed in section 3.3. The purpose of showing these results in this way is as a visual representation of reproducibility. The error bars shown are best estimate uncertainties for individual experiments. In prior research using this chamber, reproducibility for a carefully prepared reactive surface was very good. In this research however, replicate error bars do not generally overlap. Combined, this suggests some degree of heterogeneity amongst the materials. Note that this heterogeneity is also observed in UT experiments (Section 3.5). 10.0
9.0
8.0
7.0
vd, m h‐1
6.0
5.0
4.0
3.0
2.0
1.0
CP‐3
CP‐3
CP‐2
CP‐2
CP‐1
CP‐1
WP‐3
WP‐3
WP‐2
WP‐2
WP‐1
WP‐1
WD‐1
WD‐1
WCP‐1
WCP‐1
WC‐3
WC‐3
WC‐2
WC‐2
WC‐1
WC‐1
FWf‐2
FWf‐2
FWf‐1
FWf‐1
FRf‐3
FRf‐3
FRf‐3
FRf‐2
FRf‐2
FRf‐1
FRf‐1
FCf‐1
FCf‐1
FCf‐1
FC‐2
FC‐2
FC‐1
FC‐1
FC‐1
FC‐1
0.0
Figure 3‐1. Deposition velocity for every material and individual experiment derived from the 10 L chamber at Missouri S&T. 67
Figure 3‐1 shows the fractional standard error (standard error/average measurement) for deposition velocity. For more highly reactive materials, the deposition velocity is reproducible to within 10‐20%. For low‐reactivity materials, the measured deposition velocity is no better than about a factor of 1.5‐1.7. Again, we believe this reflects a real heterogeneity amongst individual (small) samples from the same material. For higher reactivity materials, 10‐20% reproducibility is actually quite good, but also “expected”. As the surface reactivity increases, the mixing conditions within the chamber begin to dominate the measurement; these conditions are nearly the same for each experiment. For lower reactivity experiments, the poorer reproducibility may reflect inherent uncertainties in the method that were not apparent. For these materials, the difference between the deposition velocity associated with the material and the chamber (0.06 m h‐1) is small and minor differences in material thickness, area, morphology, etc. may amplify differences. Chambers that allow for large material samples relative to the surface area of the chamber may help. On the other hand, the materials may actually be highly heterogeneous. For example, during manufacturing, the materials may have been handled by workers at the factory. Their skin oils (highly reactive with ozone), non‐uniformly distributed across the surface of the materials, could result in material sample that have a highly variable distribution of reactivity, even for the same lot. Therefore, it may not be possible to improve reproducibility for manufactured materials that have otherwise low surface reactivity. In spite of the manufacturing heterogeneity, it may not be necessary to improve this reproducibility. Providing a precise value for a low deposition velocity does not improve a test method and grading scale that is intended to promote highly reactive materials. A factor of 2 or even 3 may be sufficient to demonstrate that it is not sufficiently reactive. 0.70
standard error %
0.60
0.50
0.40
0.30
0.20
0.10
0.00
0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
8.0
average deposition velocity (m h‐1)
68
Figure 3‐2. Fractional standard error as a function of the average deposition velocity. The results are similar, but not identical for the reaction probability as shown in Figure 3‐3. Because the reaction probability tends to range over several orders of magnitude, the results are shown on a log scale. On this scale, the appearance of reproducibility is somewhat better. In Figure 3‐4, the fractional standard error is shown to be somewhat higher, but more uniform across the range of reaction probabilities. Overall, reproducibility was deemed sufficient for this research and for any resulting test method aimed at generating a “grade” for LEED credit. reaction probability, γ
1.0E‐04
1.0E‐05
1.0E‐06
CP‐3
CP‐3
CP‐2
CP‐2
CP‐1
CP‐1
WP‐3
WP‐3
WP‐2
WP‐2
WP‐1
WP‐1
WD‐1
WD‐1
WCP‐1
WCP‐1
WC‐3
WC‐3
WC‐2
WC‐2
WC‐1
WC‐1
FWf‐2
FWf‐2
FWf‐1
FWf‐1
FRf‐3
FRf‐3
FRf‐3
FRf‐2
FRf‐2
FRf‐1
FRf‐1
FCf‐1
FCf‐1
FCf‐1
FC‐2
FC‐2
FC‐1
FC‐1
FC‐1
FC‐1
1.0E‐07
Figure 3‐3. Reaction probability for every material and individual experiment derived from the 10 L chamber at Missouri S&T. 69
0.80
standard error %
0.70
0.60
0.50
0.40
0.30
0.20
0.10
0.00
1.00E‐06
1.00E‐05
1.00E‐04
reaction probability
Figure 3‐4. Fractional standard error as a function of the average reaction probability. Molar yields were much less reproducible in the S&T chamber as evidenced by Figure 3‐5. We believe this may be due to a combination of higher air exchange rates and high primary emission rates. We were unable to improve on this during the project, and derived best‐possible results for each material. Yields may be difficult to reproduce (Wang and Morrison, 2006) in small chambers, but have been successfully reproduced in the 48 L UT chamber (see section 3.1.2). For materials that are anticipated to result in higher yields (carpets and organic wall coatings such as FC‐1, FC‐2, WP‐2, WC‐2) the yields were consistently positive, though low relative to the same materials tested in the UT chamber. 70
1.00
0.90
2 Hour Yield
24 Hour Yield
0.80
0.70
Total yield
0.60
0.50
0.40
0.30
0.20
0.10
FC‐1
FC‐1
FC‐1
FC‐1
FC‐2
FC‐2
FCf‐1
FCf‐1
FCf‐1
FRf‐1
FRf‐1
FRf‐2
FRf‐2
FRf‐3
FRf‐3
FRf‐3
FWf‐1
FWf‐1
FWf‐2
FWf‐2
WC‐1
WC‐1
WC‐2
WC‐2
WC‐3
WC‐3
WCP‐1
WCP‐1
WD‐1
WD‐1
WP‐1
WP‐1
WP‐2
WP‐2
WP‐3
WP‐3
CP‐1
CP‐1
CP‐2
CP‐2
CP‐3
CP‐3
0.00
Figure 3‐5. Total yields for every material and individual experiment derived from the 10 L chamber at Missouri S&T. For clarity, these are not shown as speciated yields.
71
3.1.2 UT 48 L chamber Shown in Figure 3‐6 are replicate measurements (different pieces of the same material) for deposition velocity tested in the UT 48L chamber. Reproducibility is good, similar to that in the S&T chamber, with fractional standard error ranging from 0.1 to 0.2. The heterogeneity noted in section 3.1.1 is also observed here. For example, the ceiling tile (CP‐2) deposition velocity ranges from 2‐3.5 m h‐1. Note that reaction probability is not measured in the UT 48 L chamber. 5
deposition velocity (m h‐1 )
4.5
4
3.5
3
2.5
2
1.5
1
0.5
0
Figure 3‐6. Deposition velocity for every material and individual experiment derived from the UT 48 L chamber. Yields measured for the same materials are shown (speciated) in Figure 3‐7. Excluding acetone and some of the low‐yield species, reproducibility was quite good. It is inherently difficult to quantify species at low yield due to the amplified uncertainties when subtracting temporally separated emission rate measurements (primary and ozone‐induced emissions). Acetone could be the product of ozone reactions with skin oils (Weschler et al., 2007), suggesting that some of the variability could be due to workers handling the material. However, C10 should also be amplified in these cases, but was not apparent. 72
0.70
C10
C9
TA
C8
BA
C7
C6
C5
0.20
C4
C3
0.10
ACE
C2
0.60
0.50
s
d
l
e
iy
0.40
0.30
0.00
C1
Figure 3‐7. Speciated yield for every material and individual experiment derived from the UT 48 L chamber.
73
3.2 Task 2: Protocol variations Carpet FC‐1 and clay plaster WCP‐1 were subjected to parameter variations of temperature, relative humidity and ozone concentration. Further, the clay plaster was subjected to a 7 day exposure test. 3.2.1 Carpet FC­1 The deposition velocity and reaction probability were not significantly affected by temperature (15 to 31 C) or relative humidity (25‐75%). They are somewhat sensitive to the chamber ozone concentration as shown in Figure 3‐8. 10
1.0E‐04
8
reaction probability
deposition velocity (m h‐1 )
9
7
6
5
4
3
y = ‐0.0066x + 6.525
2
y = ‐2E‐07x + 8E‐05
1
0
1.0E‐05
0
100
200
300
400
0
chamber ozone concentration (ppb)
100
200
300
400
chamber ozone concentration (ppb)
Figure 3‐8. The influence of chamber ozone concentration on deposition velocity and reaction probability for carpet FC‐1 Total yields derived from FC‐1 may increase with relative humidity and temperature as shown in Figure 3‐9. However, the scatter in the results places some doubt on any statistically significant effect. There was no observed effect of chamber ozone concentration on yield, for the same reason. The inferred relative humidity effect is the opposite of that found in the large chamber for the same material (see section 3.7) 74
2 h
2 h
0.30
24 h
2 h
0.25
24 h
0.25
yield
0.20
0.15
0.10
0.20
0.15
0.05
0.05
0.00
0.00
0
20
40
60
80
0.15
0.10
0.10
0.05
24 h
0.20
yield
0.25
yield
0.30
0.35
0.30
0.00
0
10
20
30
40
0
temperature (C)
relative humidity (%)
50
100
150
chamber ozone concentration (ppb)
Figure 3‐9. The influence of relative humidity, temperature and chamber ozone concentration on yield for carpet FC‐1. 3.2.2 Clay plaster WCP­1 The deposition velocity and reaction probability were not significantly affected by temperature or relative humidity. A distinct reduction in deposition velocity and reaction probability was observed as the chamber ozone concentration was increased as shown in Figure 3‐10. 10
1.0E‐04
reaction probability
deposition velocity (m h‐1 )
9
8
7
6
5
4
3
y = ‐0.0258x + 7.3879
2
1
y = ‐3E‐07x + 5E‐05
0
1.0E‐05
0
50
100
150
0
chamber ozone concentration (ppb)
50
100
150
chamber ozone concentration (ppb)
Figure 3‐10. WCP‐1 deposition velocity (left) and reaction probability (right) as a function of chamber ozone concentration. This phenomenon indicates that the choice of concentration is important when testing materials. However, the scatter is large enough to also indicate that testing within a “range” of concentrations may be sufficient (such as between 50‐100 ppb). Shown in Figure 3‐11 are the deposition velocity and reaction probability results as a function of the total integrated uptake of ozone to the surface. The point to the far right of each figure is the final value after seven days of exposure. There appears to be a slight decrease, on average, but not statistically significant. For materials like this, a 24 h experiment appears to be sufficient to determine the deposition velocity, within the limits of uncertainty. 75
10
1.0E‐04
reaction probability
deposition velocity (m h‐1 )
9
8
7
6
5
4
3
2
1
0
1.0E‐05
0.00E+00 5.00E‐08 1.00E‐07 1.50E‐07 2.00E‐07 2.50E‐07
0.00E+00 5.00E‐08 1.00E‐07 1.50E‐07 2.00E‐07 2.50E‐07
integrated ozone uptake (mol m ‐2 )
integrated ozone uptake (mol m ‐2 )
Figure 3‐11. WCP‐1 deposition velocity (left) and reaction probability (right) as a function of integrated ozone uptake. Due to the low secondary emission rates from clay, we do not compare carbonyl yields for clay WCP‐1 in parameter variations.
76
3.3 Task 4: Materials testing in S&T 10 L chamber 3.3.1 Results by material In the following material specific results, replicates are reported as result 1, result 2, … ± typical uncertainty for individual experiment. Figures show primary and secondary emissions and yields. Because secondary emissions and yields are the result of subtracting out the primary emissions, it is possible for secondary emission rates and yields to become slightly negative for individual compounds. This reflects inherent “noise” in the emission rates and may also represent a reduced primary emission rate for some compounds as they are depleted from the material. Uncertainties are shown directly for deposition velocity, reaction probability and integrated ozone uptake. Uncertainties are not shown on emissions figures due to the cumbersome nature of showing species‐specific uncertainties on a stacked chart. Instead, refer to supplementary material for experiment level detail of uncertainties. 77
3.3.1.1 FC­1 Carpet Number of replicates: 4 Average Deposition Velocity: 4.5, 4.7, 5.2, 5.2 ± 0.4 m h‐1 Integrated Ozone Uptake: 25, 15, 25, ×10‐9 ± 3×10‐9 moles cm‐2 Average Reaction Probability: 42, 30, 33, 43 ×10‐6 ± 14×10‐6 1000
Acetone
C12
C11
C10
600
C9
400
C8
C7
200
C6
0
C5
C4
‐200
C3
C2
‐400
PE
2 h
24 h
C1
SE 2 h SE 24 h
Yield
Emission rate (μg m ‐2 h‐1 )
800
1.00
0.90
0.80
0.70
0.60
0.50
0.40
0.30
0.20
0.10
0.00
‐0.10
‐0.20
‐0.30
‐0.40
‐0.50
Acetone
C12
C11
C10
C9
C8
C7
C6
C5
C4
C3
C2
C1
2 h
24 h
Figure 3‐12. Primary and secondary emission rates (left) and yields (right) for FC‐1, averaged over all replicates. Observations: FC‐1, carpeting exhibited consistently high ozone deposition velocities, reaction probabilities and yields. Total secondary emissions were positive for this material especially evident for C9, indicating that increases in emission rates post ozone exposure dominated over the primary emission rates. Positive yields occurred as would be expected from carpet (Morrison and Nazaroff, 2002). 78
3.3.1.2 FC­2 Carpet Number of replicates: 2 Average Deposition Velocity: 4.3, 3.5 ± 0.3 m h‐1 Integrated Ozone Uptake: 19, 22 ×10‐9± 1 ×10‐9 moles cm‐2 Average Reaction Probability: 27, 19 ×10‐6± 5 ×10‐6 Yi
1000
Acetone
C12
C11
C10
600
C9
400
C8
C7
200
C6
0
C5
C4
‐200
C3
C2
‐400
PE
2 h
24 h
C1
SE 2 h SE 24 h
Yield
Emission rate (μg m ‐2 h‐1 )
800
1.00
0.90
0.80
0.70
0.60
0.50
0.40
0.30
0.20
0.10
0.00
‐0.10
‐0.20
‐0.30
‐0.40
‐0.50
Acetone
C12
C11
C10
C9
C8
C7
C6
C5
C4
C3
C2
C1
2 h
24 h
Observations: FC‐2, fabric backed carpeting exhibited high ozone deposition velocities, reaction probabilities and yields, as would be expected from carpeting. Positive yields were found for the majority of the carbonyls, with C2 aldehyde exhibiting a significant negative yield. The results found are consistent with what is expected for carpeting. When opened from packaging for sample preparation this carpet exhibited a strong odor. 79
3.3.1.3 FRf­1 Linoleum­style tile resilient flooring Number of replicates: 2 Average Deposition Velocity: 0.44, 0.27 ± 0.06 m h‐1 Integrated Ozone Uptake: 6.15, 4.78 ×10‐9± 0.48 ×10‐9 moles cm‐2 Average Reaction Probability: 1.50, 0.88 ×10‐6± 0.40 ×10‐6 1000
Acetone
C12
C11
C10
600
C9
400
C8
C7
200
C6
0
C5
C4
‐200
C3
C2
‐400
PE
2 h
24 h
C1
SE 2 h SE 24 h
Yield
Emission rate (μg m ‐2 h‐1 )
800
1.00
0.90
0.80
0.70
0.60
0.50
0.40
0.30
0.20
0.10
0.00
‐0.10
‐0.20
‐0.30
‐0.40
‐0.50
Acetone
C12
C11
C10
C9
C8
C7
C6
C5
C4
C3
C2
C1
2 h
24 h
Observations: FRf‐1, Linoleum‐style resilient flooring had relatively low deposition velocities, integrated ozone uptake and reaction probabilities. Yields for the 2 hour testing period were positive, while for the 24 hour testing period yield was fully negative, indicating that the primary emission rates dominate over the 24 hour sampling, but the 2 hour time period dominates over the primary emission rates. Linoleum style flooring is often composed of “drying oils” that can retain ozone‐reactive double‐bonds after manufacture that lead to secondary emissions. This material did not appear to generate significant amounts of secondary aldehydes from reactions with remaining drying oils (by 24 hours of exposure). 80
3.3.1.4 FRf­2 Rubber puzzle­locking tile resilient flooring Number of replicates: 2 Average Deposition Velocity: 1.42, 2.02 ± 0.21 m h‐1 Integrated Ozone Uptake: 12.5, 16.4 ×10‐9± 0.8 ×10‐9 moles cm‐2 Average Reaction Probability: 5.70, 9.33 ×10‐6± 1.28 ×10‐6 1000
Acetone
C12
C11
C10
600
C9
400
C8
C7
200
C6
0
C5
C4
‐200
C3
C2
‐400
PE
2 h
24 h
C1
SE 2 h SE 24 h
Yield
Emission rate (μg m ‐2 h‐1 )
800
1.00
0.90
0.80
0.70
0.60
0.50
0.40
0.30
0.20
0.10
0.00
‐0.10
‐0.20
‐0.30
‐0.40
‐0.50
Acetone
C12
C11
C10
C9
C8
C7
C6
C5
C4
C3
C2
C1
2 h
24 h
Observations: FRf‐2 rubber puzzle‐locking tile resilient flooring exhibited moderate deposition velocities and reaction probabilities. The material also exhibited relatively high emission rates consistently throughout testing, which reduced our certainty in secondary emission rates and yields. That said,yields were mostly positive. The material retained a definitive odor, similar to rubber tires. This probably is related to the high primary emission rates. 81
3.3.1.5 FRf­3 Bio­based tiles, resilient flooring Number of replicates: 3 Average Deposition Velocity: 0.34, 0.34, 0.25 ± 0.03 m h‐1 Integrated Ozone Uptake: 5.84, 6.78, 3.99 ×10‐9± 0.25 ×10‐9 moles cm‐2 Average Reaction Probability: 1.11, 1.13, 0.83 ×10‐6± 0.39 ×10‐6 1000
Acetone
C12
C11
C10
600
C9
400
C8
C7
200
C6
0
C5
C4
‐200
C3
C2
‐400
PE
2 h
24 h
C1
SE 2 h SE 24 h
Yield
Emission rate (μg m ‐2 h‐1 )
800
1.00
0.90
0.80
0.70
0.60
0.50
0.40
0.30
0.20
0.10
0.00
‐0.10
‐0.20
‐0.30
‐0.40
‐0.50
Acetone
C12
C11
C10
C9
C8
C7
C6
C5
C4
C3
C2
C1
2 h
24 h
Observations: FRf‐3, bio‐ based resilient floor tile, exhibited low deposition velocities and reaction probabilities. The emission rates were also low in comparison to other materials. Yields for the 24 hour sample were large, with both very large negative and positive yields observed. The 24 hour emission rates dominate over both the 2 hour emission rates and the primary emission rates. Positive yields are dominated by C8‐C12 compounds, possibly indicating indicating reactions with fatty acids remaining in the tiles. 82
3.3.1.6 FCf­1 Porcelain floor tile Number of replicates: 3 Average Deposition Velocity: 0.29, 0.17, 0.43 ± 0.07 m h‐1 Integrated Ozone Uptake: 7.56, 6.39, 9.65 ×10‐9± 0.83 ×10‐9 moles cm‐2 Average Reaction Probability: 1.11, 1.13, 0.83 ×10‐6± 0.39 ×10‐6 1000
Acetone
C12
C11
C10
600
C9
400
C8
C7
200
C6
0
C5
C4
‐200
C3
C2
‐400
PE
2 h
24 h
C1
SE 2 h SE 24 h
Yield
Emission rate (μg m ‐2 h‐1 )
800
1.00
0.90
0.80
0.70
0.60
0.50
0.40
0.30
0.20
0.10
0.00
‐0.10
‐0.20
‐0.30
‐0.40
‐0.50
Acetone
C12
C11
C10
C9
C8
C7
C6
C5
C4
C3
C2
C1
2 h
24 h
Observations: FCf‐1, porcelain floor tile, exhibited consistently low deposition velocities, and integrated ozone uptakes. Yields were low with high negative yields indicating that they are effectively zero. Primary emission rates were higher than both the 2 hour emissions and the 24 hour emissions, creating negative secondary emissions for all of the carbonyls except acetone. The porcelain tile was glazed which is probably responsible for the low deposition velocities. However, small amounts of glue were found on its surface, from shipping. Although the glue was removed prior to testing, residues could have contributed to the high primary emission rates. 83
3.3.1.7 FWf­1 Renewable wood flooring Number of replicates: 2 Average Deposition Velocity: 0.97, 0.38 ± 0.21 m h‐1 Integrated Ozone Uptake: 20.1, 5.1 ×10‐9± 5.3 ×10‐9 moles cm‐2 Average Reaction Probability: 3.70, 1.26 ×10‐6± 2.24 ×10‐6 1000
Acetone
C12
C11
C10
600
C9
400
C8
C7
200
C6
0
C5
C4
‐200
C3
C2
‐400
PE
2 h
24 h
C1
SE 2 h SE 24 h
Yield
Emission rate (μg m ‐2 h‐1 )
800
1.00
0.90
0.80
0.70
0.60
0.50
0.40
0.30
0.20
0.10
0.00
‐0.10
‐0.20
‐0.30
‐0.40
‐0.50
Acetone
C12
C11
C10
C9
C8
C7
C6
C5
C4
C3
C2
C1
2 h
24 h
Observations: FWf‐1 renewable wood flooring exhibited moderate deposition velocities. The flooring had moderate yields for the 2 hour sample, with exceptionally high yields for the 24 hour sample, in particular from C6, C7, C9 and C10 aldehydes were all present in abundance. High yields are expected from a wood based flooring material, but polymer‐based finishes are expected to reduce reactivity with ozone. The yields, dominated by C6 and C10 aldehydes may suggest reactions with human skin oils. Our protocol was to use fresh gloves when handling all materials; the oils may have come from handling at the manufacturer/shipper. 84
3.3.1.8 FWf­2 Renewable wood flooring Average Deposition Velocity: 0.33, 0.76 ± 0.15 m h‐1 Integrated Ozone Uptake: 7.05, 6.84 ×10‐9± 0.09 ×10‐9 moles cm‐2 Average Reaction Probability: 2.8, 1.1 ×10‐6± 0.6 ×10‐6 1000
Acetone
C12
C11
C10
600
C9
400
C8
C7
200
C6
0
C5
C4
‐200
C3
C2
‐400
PE
2 h
24 h
C1
SE 2 h SE 24 h
Yield
Emission rate (μg m ‐2 h‐1 )
800
1.00
0.90
0.80
0.70
0.60
0.50
0.40
0.30
0.20
0.10
0.00
‐0.10
‐0.20
‐0.30
‐0.40
‐0.50
Acetone
C12
C11
C10
C9
C8
C7
C6
C5
C4
C3
C2
C1
2 h
24 h
Observations: FWf‐2, finished bamboo flooring exhibited relatively low ozone deposition velocities, reaction probabilities and yields. Total secondary emissions were negative for this material, indicating that the reduction in primary emission rates dominated any increase in the emission rate of reaction formed carbonyls. Positive yields are shown with their negative yield counterparts. We conclude that the yields are nearly indistinguishable from zero. Low reactivity of smooth‐finished wood flooring is to be expected. 85
3.3.1.9 WC­1 Cork wall tiles Number of replicates: 2 Average Deposition Velocity: 0.81, 0.68 ± 0.05 m h‐1 Integrated Ozone Uptake: 10.7, 8.3 ×10‐9± 0.8 ×10‐9 moles cm‐2 Average Reaction Probability: 2.7, 2.2 ×10‐6± 0.2 ×10‐6 1000
Acetone
C12
C11
C10
600
C9
400
C8
C7
200
C6
0
C5
C4
‐200
C3
C2
‐400
PE
2 h
24 h
C1
SE 2 h SE 24 h
Yield
Emission rate (μg m ‐2 h‐1 )
800
1.00
0.90
0.80
0.70
0.60
0.50
0.40
0.30
0.20
0.10
0.00
‐0.10
‐0.20
‐0.30
‐0.40
‐0.50
Acetone
C12
C11
C10
C9
C8
C7
C6
C5
C4
C3
C2
C1
2 h
24 h
Observations: WC‐1, cork wall tile, exhibited relatively low deposition velocities, and very low reaction probabilities. 2 hour yields of C8‐C12 aldehydes were positive, while 24 hour yields were nearly indistinguishable from zero. Primary emissions were relatively low for this material, suggesting that the 2 h results reflect true (positive) secondary emission rates for those compounds. Cork tile was expected to exhibit higher yields due to its composition (cork) and the presence of an organic adhesive. 86
3.3.1.10 WC­2 Acoustical Wall Panels Number of replicates: 2 Average Deposition Velocity: 6.6, 6.0 ± 0.24 m h‐1 Integrated Ozone Uptake: 29, 27 ×10‐9± 2 ×10‐9 moles cm‐2 Average Reaction Probability: 101, 65 ×10‐6± 55 ×10‐6 1000
Acetone
C12
C11
C10
600
C9
400
C8
C7
200
C6
0
C5
C4
‐200
C3
C2
‐400
PE
2 h
24 h
C1
SE 2 h SE 24 h
Yield
Emission rate (μg m ‐2 h‐1 )
800
1.00
0.90
0.80
0.70
0.60
0.50
0.40
0.30
0.20
0.10
0.00
‐0.10
‐0.20
‐0.30
‐0.40
‐0.50
Acetone
C12
C11
C10
C9
C8
C7
C6
C5
C4
C3
C2
C1
2 h
24 h
Observations: WC‐2 acoustical wall panels exhibited very high primary emission rates, deposition velocities, integrated ozone uptake and average reaction probabilities. The 2 hour yields are very high, with the 24 hour yields being much lower, though evidently greater than zero. As expected from a textile (similar to carpet) C9 was produced emitted in large quantities. 87
3.3.1.11 WC­3 Fabric wall covering Number of replicates: 2 Average Deposition Velocity: 1.32, 1.25 ± 0.05 m h‐1 Integrated Ozone Uptake: 22, 16 ×10‐9± 2 ×10‐9 moles cm‐2 Average Reaction Probability: 5.5, 5.1 ×10‐6± 0.6 ×10‐6 1000
Acetone
C12
C11
C10
600
C9
400
C8
C7
200
C6
0
C5
C4
‐200
C3
C2
‐400
PE
2 h
24 h
C1
SE 2 h SE 24 h
Yield
Emission rate (μg m ‐2 h‐1 )
800
1.00
0.90
0.80
0.70
0.60
0.50
0.40
0.30
0.20
0.10
0.00
‐0.10
‐0.20
‐0.30
‐0.40
‐0.50
Acetone
C12
C11
C10
C9
C8
C7
C6
C5
C4
C3
C2
C1
2 h
24 h
Observations: WC‐3 fabric wall covering exhibited moderate deposition velocities and low reaction probabilities. Both yield and secondary emissions are close to zero. Emission rates of carbonyls were fairly consistent throughout the experiment indicating that little in the way of secondary emissions were produced. Although a “fabric” wall covering, this material appears to have a glossy coating that could act as a barrier to reaction with the fibers. 88
3.3.1.12 WP­1 Latex paint and primer Number of replicates: 2 Average Deposition Velocity: 0.54, 0.93 ± 0.14 m h‐1 Integrated Ozone Uptake: 8.9, 8.5 ×10‐9± 0.8 ×10‐9 moles cm‐2 Average Reaction Probability: 1.9, 3.5 ×10‐6± 1.5×10‐6 1000
Acetone
C12
C11
C10
600
C9
400
C8
C7
200
C6
0
C5
C4
‐200
C3
C2
‐400
PE
2 h
24 h
C1
SE 2 h SE 24 h
Yield
Emission rate (μg m ‐2 h‐1 )
800
1.00
0.90
0.80
0.70
0.60
0.50
0.40
0.30
0.20
0.10
0.00
‐0.10
‐0.20
‐0.30
‐0.40
‐0.50
Acetone
C12
C11
C10
C9
C8
C7
C6
C5
C4
C3
C2
C1
2 h
24 h
Figure 3‐13. Primary and secondary emission rates (left) and yields (right) for WP‐1, averaged over all replicates. Observations: WP‐1 latex paint and primer, exhibited low ozone deposition velocities, and modest to low yields. The primary emissions rates were significantly lower than the 2 hour and the 24 hour emissions which created positive secondary emissions, though still very low. Yields were small with the yield of C8 in the 2 hour yield being mirrored by a negative C2 yield, while the 24 hour yields were dominated by the negative C2 yield. Lower relative primary emission rates are consistent with dried paint material that has had a chance to air out. 89
3.3.1.13 WP­2 Clay paint Number of replicates: 2 Average Deposition Velocity: 8.2, 6.8 ± 0.5 m h‐1 Integrated Ozone Uptake: 27, 30 ×10‐9± 3 ×10‐9 moles cm‐2 Average Reaction Probability: 69, 44 ×10‐6± 5 ×10‐6 1000
Acetone
C12
C11
C10
600
C9
400
C8
C7
200
C6
0
C5
C4
‐200
C3
C2
‐400
PE
2 h
24 h
C1
SE 2 h SE 24 h
Yield
Emission rate (μg m ‐2 h‐1 )
800
1.00
0.90
0.80
0.70
0.60
0.50
0.40
0.30
0.20
0.10
0.00
‐0.10
‐0.20
‐0.30
‐0.40
‐0.50
Acetone
C12
C11
C10
C9
C8
C7
C6
C5
C4
C3
C2
C1
2 h
24 h
Observations: WP‐2 clay paint exhibited high deposition velocities, reaction probabilities and ozone uptakes, with moderate yields. The 2‐h yields were dominated by C6 and C9 and C9 dominating in the 24 hour yield. The paint binding agent and composition of the clay could both lead to the high reactivity of the clay paint. 90
3.3.1.14 WP­3 Collagen paint Number of replicates: 2 Average Deposition Velocity: 0.7, 1.0 ± 0.1 m h‐1 Integrated Ozone Uptake: 10, 10 ×10‐9± 1 ×10‐9 moles cm‐2 Average Reaction Probability: 2.5, 3.8 ×10‐6± 0.6 ×10‐6 1000
Acetone
C12
C11
C10
600
C9
400
C8
C7
200
C6
0
C5
C4
‐200
C3
C2
‐400
PE
2 h
24 h
C1
SE 2 h SE 24 h
Yield
Emission rate (μg m ‐2 h‐1 )
800
1.00
0.90
0.80
0.70
0.60
0.50
0.40
0.30
0.20
0.10
0.00
‐0.10
‐0.20
‐0.30
‐0.40
‐0.50
Acetone
C12
C11
C10
C9
C8
C7
C6
C5
C4
C3
C2
C1
2 h
24 h
Observations: WP‐3 collagen paint had low deposition velocities and reaction probability with moderate ozone uptake. The yields were dominated by the negative yields with negligible positive yields. This suggests that the material composition is not amenable to ozone reactions. Collagen is a mixture of proteins composed of amino acids.The structure of collagen does not suggest that it should react with ozone. 91
3.3.1.15 WCP­1 Clay plaster Number of replicates: 2 Average Deposition Velocity: 5.0, 4.1 ± 0.3 m h‐1 Integrated Ozone Uptake: 28, 24 ×10‐9± 2 ×10‐9 moles cm‐2 Average Reaction Probability: 25, 19 ×10‐6± 5 ×10‐6 1000
Acetone
C12
C11
C10
600
C9
400
C8
C7
200
C6
0
C5
C4
‐200
C3
C2
‐400
PE
2 h
24 h
C1
SE 2 h SE 24 h
Yield
Emission rate (μg m ‐2 h‐1 )
800
1.00
0.90
0.80
0.70
0.60
0.50
0.40
0.30
0.20
0.10
0.00
‐0.10
‐0.20
‐0.30
‐0.40
‐0.50
Acetone
C12
C11
C10
C9
C8
C7
C6
C5
C4
C3
C2
C1
2 h
24 h
Observations: WCP‐1 Clay Plaster exhibited high deposition velocities, ozone uptake and reaction probabilities. It also had negligible yields and secondary emissions. The primary emission rates dominate over the 2 hour and the 24 hour rates, indicating that there is low chemical reactivity with ozone within the clay plaster. The clay itself probably accounts for such a high reactivity. 92
3.3.1.16 WD­1 Recycled content drywall Number of replicates: 2 Average Deposition Velocity: 5.3, 7.7 ± 0.8 m h‐1 Integrated Ozone Uptake: 50, 25 ×10‐9± 9 ×10‐9 moles cm‐2 Average Reaction Probability: 27, 58 ×10‐6± 22 ×10‐6 1000
Acetone
C12
C11
C10
600
C9
400
C8
C7
200
C6
0
C5
C4
‐200
C3
C2
‐400
PE
2 h
24 h
C1
SE 2 h SE 24 h
Yield
Emission rate (μg m ‐2 h‐1 )
800
1.00
0.90
0.80
0.70
0.60
0.50
0.40
0.30
0.20
0.10
0.00
‐0.10
‐0.20
‐0.30
‐0.40
‐0.50
Acetone
C12
C11
C10
C9
C8
C7
C6
C5
C4
C3
C2
C1
2 h
24 h
Observations: WD‐1 drywall exhibited high deposition velocities, ozone uptakes and reaction probabilities which would be expected from previous research done with drywall (Kunkel et al., 2008). Some compounds exhibited positive yields at 2 hours, but 24 h yields are negligible. Primary emission rates are much higher than would be expected for drywall, possibly due to contamination from shipping and storage. 93
3.3.1.17 CP­1 Ceiling tile Number of replicates: 2 Average Deposition Velocity: 7.63, 5.87 ± 0.62 m h‐1 Integrated Ozone Uptake: 31.8, 43.0 ×10‐9± 4.0 ×10‐9 moles cm‐2 Average Reaction Probability: 59.2, 33.8 ×10‐6± 11.5 ×10‐6 1000
Acetone
C12
C11
C10
600
C9
400
C8
C7
200
C6
0
C5
C4
‐200
C3
C2
‐400
PE
2 h
24 h
C1
SE 2 h SE 24 h
Yield
Emission rate (μg m ‐2 h‐1 )
800
1.00
0.90
0.80
0.70
0.60
0.50
0.40
0.30
0.20
0.10
0.00
‐0.10
‐0.20
‐0.30
‐0.40
‐0.50
Acetone
C12
C11
C10
C9
C8
C7
C6
C5
C4
C3
C2
C1
2 h
24 h
Observations: CP‐1 ceiling tile exhibited high deposition velocities, ozone uptake and reaction probability, possibly due to the porous nature of the coating allowing the ozone to interact with mineral fiber underneath. The secondary emissions and yields were clearly positive for both 2 and 24 h results. No specific compound dominated yields (on a molar basis). 94
3.3.1.18 CP­2 Ceiling tile Number of replicates: 2 Deposition Velocity: 1.64,2.54 ± 0.32 m hr‐1 Integrated Ozone Uptake: 21.1, 16.7 ×10‐9 ± 1.6 ×10‐9 moles cm‐2 Reaction Probability: 13.5, 6.9 ×10‐6 ± 3.9 ×10‐6 1000
Acetone
C12
C11
C10
600
C9
400
C8
C7
200
C6
0
C5
C4
‐200
C3
C2
‐400
PE
2 h
24 h
C1
SE 2 h SE 24 h
Yield
Emission rate (μg m ‐2 h‐1 )
800
1.00
0.90
0.80
0.70
0.60
0.50
0.40
0.30
0.20
0.10
0.00
‐0.10
‐0.20
‐0.30
‐0.40
‐0.50
Acetone
C12
C11
C10
C9
C8
C7
C6
C5
C4
C3
C2
C1
2 h
24 h
Figure 3‐14. Primary and secondary emission rates (left) and yields (right) for CP‐2, averaged over all replicates. Observations: CP‐2, ceiling tile exhibited moderate depositions velocities, ozone uptake and reaction probabilities with negligible yields. Secondary emissions were also negligible. 95
3.3.1.19 CP­3 Ceiling tile Number of replicates: 2 Average Deposition Velocity: 6.84, 5.57 ± 0.45 m h‐1 Integrated Ozone Uptake: 28.5, 24.9 ×10‐9± 1.8 ×10‐9 moles cm‐2 Average Reaction Probability: 44.7, 30.1 ×10‐6± 11.7 ×10‐6 1000
Acetone
C12
C11
C10
600
C9
400
C8
C7
200
C6
0
C5
C4
‐200
C3
C2
‐400
PE
2 h
24 h
C1
SE 2 h SE 24 h
Yield
Emission rate (μg m ‐2 h‐1 )
800
1.00
0.90
0.80
0.70
0.60
0.50
0.40
0.30
0.20
0.10
0.00
‐0.10
‐0.20
‐0.30
‐0.40
‐0.50
Acetone
C12
C11
C10
C9
C8
C7
C6
C5
C4
C3
C2
C1
2 h
24 h
Observations: CP‐3 ceiling tile exhibited high deposition velocities, reaction probabilities and ozone uptake, with moderate yields at 2 hours and negligible positive yields at 24 hours. 96
3.3.2 Summary of results from19 materials in S&T 10 L chamber Shown in Table 3‐1 are experimental averages (averaged over all samples) for the primary parameters sought in these experiments. The uncertainty (±) is the largest of either uncertainty associated with an individual experiment or the standard deviation of all measurements. Table 3‐1. Summary of results for all green building materials. Shown are averages for multiple materials and multiple measurements within a single experiment. ID description FC‐1 FC‐2 FRf‐1 Deposition velocity (m h‐1) Vd ± Flooring recycled carpet fabric backed carpet bio‐based resilient tile FRf‐2 puzzle‐locking tiles FRf‐3 bio‐based resilient tiles FCf‐1 porcelain clay tile FWf‐1 finished hardwood floor FWf‐2 finished bamboo floor Wall coverings/coatings WC‐1 cork wall tiles WC‐2 fabric acoustical wall panel WC‐3 fabric wall covering WP‐1 latex paint and primer WP‐2 clay based paint WP‐3 collagen based paint WCP‐1 clay plaster wall coating WD‐1 recycled drywall Ceiling materials CP‐1 mineral fiber ceiling tile CP‐2 perlite ceiling tile CP‐3 fiberglass ceiling tile Reaction probability (× 106) ± γ
Yield y ± 4.9
3.9
0.4
0.6
36.9
23.0
13.5 6.2 0.11 0.17 0.07
0.19
0.4
1.7
0.1
0.4
1.2
7.5
0.4 2.6 0.11 0.08 0.10
0.09
0.3
0.3
0.1
0.1
1.0
1.6
0.4 0.9 0.32 0.18 0.30
0.21
0.7
0.4
2.5
2.2 0.40 0.56
0.5
0.3
1.9
1.2 0.05 0.06
0.7
0.1
2.5
0.3 0.04 0.05
6.3
1.3
0.5
0.1
83.2
5.3
55.2 0.6 0.48 0.02 0.33
0.03
0.7
7.5
0.9
0.3
1.0
0.2
2.7
56.7
3.2
1.5 18.0 1.0 0.03 0.18 0.00 0.05
0.06
0.00
4.6
6.5
0.6
1.7
22.0
42.4
4.7 21.5 0.00 0.04 0.00
0.06
6.8
2.1
6.2
1.2
0.6
0.9
46.5
10.2
37.4
18.0 4.6 11.7 0.10 0.03 0.08 0.04
0.04
0.05
97
Shown in Figure 3‐15 are the deposition velocity results, sorted from highest to lowest. The highest value is for WP‐2, the clay based paint. However, this material also exhibited fairly high secondary emission rates and yields, and is probably not a good choice for ozone control in buildings. Carpets CP‐1 and 3 and WC‐2, the fabric acoustical wall panel, also have high deposition velocities, but again had high secondary emissions of carbonyls. Drywall WD‐1 and WCP‐1, the clay plaster material had a fairly high deposition velocity, but exhibited little in the way of secondary emission rates and rank highly as a desirable material for ozone control in buildings. WP‐2
CP‐1
WD‐1
WC‐2
CP‐3
FC‐1
WCP‐1
FC‐2
CP‐2
FRf‐2
WC‐3
WP‐3
WC‐1
WP‐1
FWf‐1
FWf‐2
FRf‐1
FRf‐3
FCf‐1
0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
8.0
9.0
deposition velocity (m h‐1)
Figure 3‐15 All green building materials ranked by overall average deposition velocities. 98
3.4 Task 3a: Parallel lab comparison The results of the parallel lab comparison on three materials are shown in Figure 3‐16 and Figure 3‐17. Qualitatively, the trends are the same for both chambers: carpet has a high deposition velocity, ceiling tile is medium, painted wall‐board is low. However, for FC‐1 (Interface carpet), there is a substantial difference in the deposition velocity as measured in the two chambers. The difference is larger than the range of individual material measurements for each chamber. This is likely due to the difference in mixing characteristics of each chamber. The UT chamber has an air exchange rate 5 times lower (2 vs 10 h‐1) than the S&T chamber and is anticipated to have lower internal air velocities. Lower mixing internally would increase gas‐
phase boundary layer resistance to ozone uptake on the carpet, resulting in a lower measurement of the material’s deposition velocity. As the surface reactivity decreases, the difference between the two chambers is anticipated to diminish as material surface resistance dominates over chamber mixing characteristics. The results for ceiling tile are similar, but border‐line significantly different for the painted drywall. It is unclear why a low‐reactivity surface like this would result in different measurements in the two chambers. The S&T results mirror more closely the large chamber results (section 3.7.1) with deposition velocities of 5.5, 2.3, 0.65 m h‐1 for FC‐1, CP‐2 and WP‐1 respectively. 6.0
deposition velocity (m h‐1 )
5.0
4.0
3.0
UT 48 L
S&T 10 L
2.0
1.0
0.0
FC‐1
CP‐2
WP‐1
Figure 3‐16. Comparison of deposition velocities as measured on multiple pieces of carpet, ceiling tile and painted wallboard in two different laboratory chambers. A comparison of yields derived from S&T and UT chambers for these three materials is shown in Figure 3‐17. Shown are averages over multiple experiments for each lab. Total yields and specific species yields do not correlate. Total S&T yields are consistently lower than those measured at UT. We believe this is due to two phenomena: 1) the S&T air exchange rate is 5 times higher. While this, by itself, should not significantly influence yields, the measured concentration at the outlet of the S&T chamber (relative to the inlet or background) will be much lower. Since molar yields are dependent on subtracting the primary emissions from the 99
ozone‐exposed emission rates, smaller differences result in larger uncertainties. 2) We observed substantially higher primary emission rates in S&T chambers relative to UT chambers for the same materials. This high emission rate must be subtracted from a slightly higher ozone‐
exposed emission rate which results in larger uncertainty and even “negative” secondary emission rates if the relative uncertainty encompasses the absolute increase in emission rates. This higher primary emission rate may be the result of the differences in air exchange rates that lead to higher “limit of detection” for emission rates. We also suspect that there may be a laboratory specific effect as well: higher background aldehyde concentrations in the laboratory (at S&T) may temporarily contaminate the specimens during preparation and transfer from storage to the chamber. If this is the case, there will be a tendency for yields to be smaller as the background primary emission rates would not necessarily be constant (desorbing carbonyl species result in slowly diminishing background emission rates). The UT 48L chamber results compare well (for carpet) with the UT large chamber yield results for heavy aldehydes. The yields do not compare as well for other materials. 0.50
Acetone
0.45
C10
0.40
C9
0.35
C8
0.30
d
l
0.25
ie
y
0.20
C7
C6
0.15
C5
0.10
C4
0.05
C3
0.00
FC‐1 FC‐1 (S&T) (UT)
CP‐2 CP‐2 (S&T) (UT)
WP‐1 WP‐1 (S&T) (UT)
C2
C1
Figure 3‐17. Comparison of aldehyde yields from carpet, ceiling tile and painted wallboard for UT and S&T reactors. The UT chamber yields appear to be much more robust and reproducible than the S&T yields, suggesting that it may be prudent to use larger chambers with lower air exchange rates to derive secondary emissions and yield values at commercial labs. However, the smaller S&T chamber deposition velocity results compare better with results derived from the full‐scale UT chamber facility. A chamber that combines low air exchange rates with good mixing may be a better choice for a commercial system.
100
3.5 Task 3b Field Exposure and aging of selected materials Experimental results for the field analysis are presented in this section. Ozone deposition velocities are described first, followed by primary and secondary emissions from test materials. The associations between field environmental parameters and materials characteristics are then discussed. 3.5.1 OZONE SCAVENGING Ozone deposition velocities averaged over the six months of experiments for each material at each field location are presented in Figure 3‐18. Error bars represent the standard deviation for deposition velocities determined across all six months. Figure 1 allows a comparison of materials against one another as well as the effect of specific locations on the ozone scavenging potential of the materials. Note that since air flow conditions in chambers did not change during the experimental program, differences in deposition velocity should have been due solely to differences in material reactivity with ozone, i.e., reaction probability. Higher air flows would have probably lead to greater differences in deposition velocity between materials as transport limitations to ozone deposition would have been reduced and effects of reactivity magnified (Cano‐Ruiz et al., 1993; Grøntoft et al., 2004a). Activated carbon was the most efficient material at removing ozone, with ozone deposition velocities in laboratory chambers ranging from 2.5 to 3.8 m h‐1. Ozone deposition velocities measured for carpet and ceiling tile were slightly less than those for activated carbon, ranging from 2.0 to 3.0 m h‐1 and 2.2 to 3.2 m h‐1, respectively. These results (similarity between deposition velocities for carpet and ceiling tile) are in contrast to those described for large chamber experiments and likely reflect the importance of transport resistance to overall removal to materials in the smaller test chambers. Nevertheless, the fact that ozone deposition velocities for painted gypsum wallboard were 2.5 to 3 times lower than for the other three materials, in the range of 0.7 to 1.3 m h‐1, suggests that surface reaction resistance was also important during small chamber experiments. 101
Figure 3‐18. Ozone deposition velocity on test material samples averaged over time. Figure 3‐18 also shows that all three green building materials present a similar trend of reduced ozone deposition velocity for the samples that were placed in the office field location. Environmental conditions in other locations do not seem to have had an effect that influenced several materials, as did the office location. The office location is the only one that was not situated in a residential setting. It may be that HVAC operation or custodial cleaning in the office building affected material surfaces by leading to deposition of less reactive particles or gases on the surfaces of specimens; surface soiling was not visible to the naked eye. Ozone deposition velocities for each material averaged over all locations are presented in Figure 3‐19. Standard deviations around mean deposition velocities are also presented. Spatially‐
averaged ozone deposition velocities for activated carbon, ceiling tile and painted gypsum wallboard exhibited little variation over time. There was a slight increase in ozone removal for activated carbon and a very slight decrease for painted gypsum wallboard. This finding is important in that it indicates that after a relatively long period of time these materials remain consistent at removing ozone from indoor air. Carpet exhibited a stronger trend of decreased ozone removal over time, starting with ozone deposition velocities as high as activated carbon but ending with a deposition that was lower than ceiling tiles. After six months in the field, the carpet removed about 30% less ozone than it did initially. 102
Figure 3‐19. Ozone deposition velocity on material samples averaged over all locations. Figure 3‐20 shows an entire set of results for ceiling tile. Each cluster of bars represents one field location, with bars representing deposition velocities measured from month 0 to month 6. Error bars were calculated using an error propagation analysis. The graph shows slight variations between the different measurements and between locations; few are out of the uncertainty range, which is also true for other materials (graphs for other materials are provided in Supplementary Information). The office location exhibited lower ozone deposition velocities than other locations. This is also seen in the other material specific graphs for carpet and painted gypsum wallboard (see Supplementary Information). Isolated increases in reactivity could be due to changes in activity patterns in the field locations leading to a different level of soiling of the materials, which can affect ozone reactivity. 103
Figure 3‐20. Ozone deposition velocities for ceiling tile. 3.5.2 BY­PRODUCT EMISSIONS Primary emissions refer to emissions that occurred during testing, before ozonated air was introduced into the test chambers. Secondary emissions were measured after ozonated air was introduced into the chambers. By‐product emissions averaged over all locations are presented in Figure 3‐21 for each of the four materials tested. Figure 3‐21 allows a comparison of primary and secondary emissions of the materials and their overall evolution over time. 104
Figure 3‐21. By‐product emissions averaged over all locations for all four test materials. For activated carbon primary emissions decreased over time while secondary emissions tended to increase slightly. However, as expected emissions from activated carbon were lower than any of the other three materials for both primary and secondary emissions. The relatively low emissions from activated carbon were dominated by acetaldehyde (22% to 59% by mass) as well as formaldehyde, particularly for secondary emissions (5% to 35%). The three green building materials had some similarities in their by‐product emissions. All three materials exhibited higher secondary emissions than primary emissions for the conditions studied (inlet ozone of 147 ± 10 ppb). In each case, secondary emissions were dominated by nonanal. This is consistent with results from Wang et al. (2006) who tested secondary emissions of various indoor surfaces in four homes between one and fourteen years old. For similar test conditions, they also observed higher secondary emissions than primary emissions, also dominated by nonanal. Nonanal is a common ozone reaction product associated with oleic acid and other compounds with a carbon=carbon double bond on the 9th carbon in a hydrocarbon chain. Important differences also separated the green building materials with respect to by‐product emissions. Similar to results for large chamber experiments, carpet was the material that had the highest primary and secondary by‐product emissions. Even though initial primary and secondary emission rates were relatively high, there was a noticeable decay in emissions 105
between the initial measurement and the one made after three months; after three months, primary and secondary emissions from carpet decreased by about 60% from their initial level. After that period, primary emissions were similar at month 6, while secondary emissions decreased slightly. Ceiling tile exhibited a different temporal variation for by‐product emissions. While primary emissions decreased by 50% during the six‐month study period, secondary emissions increased by 70% over the same period. Ceiling tiles were porous and might have adsorbed some gases or retained particles deposited on their surfaces at field locations. Alternately, oils such as oleic acid may have condensed onto the material in buildings/locations where, for example, cooking with oils took place. It is possible that these gases, particles, or condensed oils later reacted with ozone during laboratory tests, explaining an increase in secondary emissions from the material, although one might expect the same contaminants to deposit on other materials in the same environments. Finally, painted gypsum wallboard exhibited emission patterns that were different from the other two green test materials. Primary and secondary emissions were the highest initially but dropped by 36% and 50%, respectively, during the first three months. However, emissions then increased during the next three months by 23% and 30%, respectively. It is difficult to speculate how emissions would evolve beyond the six‐month test period. Accounting for both ozone scavenging as well as by‐product emissions results, it is clear that none of three green test materials can match the fibrous activated carbon mat. However, from a practical standpoint (aesthetics and cost) the ceiling tile performed relatively well compared against the other two green materials. After several months it had a higher ozone deposition velocity than carpet and also sustained relatively low primary and secondary product emissions over the six‐month study period. Primary emissions were relatively consistent across locations. More variations were observed for secondary emissions, possibly because of differences in environmental conditions at each field location. On the one hand, it appears that over all locations secondary emissions from carpet are the highest followed by ceiling tile, painted gypsum wallboard and finally activated carbon, which suggests that the nature of the material itself determines in part the extent of secondary emissions that will be produced. Conversely, the test house, study room and office samples had secondary emission rates in the same range while the bedroom, and even more so the kitchen samples, exhibited higher emission rates, suggesting that soiling environmental conditions such as soiling affect secondary emissions. Results for primary and secondary emissions at the kitchen location for all four materials are shown in Figure 3‐22. The primary emissions for this location do not exhibit particular trends compared to other locations. However, the secondary emissions are unique to this location (results for other locations are presented in Supplementary Information). Activated carbon, 106
ceiling tile and painted gypsum wallboard each had increased overall secondary emissions over time. The ceiling tile was especially affected, with overall secondary emissions after six months that increased sixty five times initial secondary emissions. Secondary emissions for painted gypsum wallboard doubled in six months while secondary emissions for activated carbon remained very low but increased by a factor of five. On the other hand, carpet did not seem to be affected by its location (on the floor) in the same way; its emissions decreased after three months before very slightly increasing in the next three months. One possible explanation for these results is that ozone reacts with chemicals emitted during cooking events that rise in hot cooking plumes and reach elevated materials, but do not interact as much with floor materials. Vegetable cooking oils contain unsaturated fatty acids, such as oleic acid, that react with ozone to form several oxygenated compounds including aldehydes (Sadowska et al., 2008). Such interactions have been observed in simulated cooking events by (Wang et al., 2005), who showed increased emissions of heavy aldehydes, especially hexanal and nonanal, from kitchen surfaces. Similar interactions between ozone and compounds emitted during cooking events and adsorbed or condensed onto materials could explain the secondary emissions observed during laboratory tests in this study. The results tend to validate this hypothesis as all the materials that were set on shelves high above the floor, within reach of cooking oil fumes, showed a similar trend of increased secondary by‐product emissions. On the other hand, carpet, that was placed on the floor, out of reach of cooking fumes, did not show such a trend. However, as described above it had primary and secondary emissions that decayed with time. Oleic acid may have also deposited on the carpet by its effects were not as noticeable because of the otherwise lower secondary emissions from carpet with time. 107
Figure 3‐22. By‐product emissions for samples from the Kitchen location. 3.5.3 ASSOCIATION WITH ENVIRONMENTAL PARAMETERS Environmental parameters (temperature, RH, dustiness, TVOCs) were measured for each month of the study at field locations where material samples were installed. Single variable associations were explored using linear correlations between an environmental parameter and either ozone deposition velocity, primary or secondary carbonyl emissions. Correlations between ozone deposition velocities and field parameters were studied for each material. The association plots and tables summarizing correlation results can be found in Supplementary Information. For all parameters measured in the field, the associations between field conditions and ozone deposition velocities measured in chamber tests are weak, with R2 smaller than 0.2 for most combinations of environmental parameter and material. Only two combinations had R2 values greater than 0.2, with R2 = 0.32 and 0.24 for ozone deposition on carpet versus RH and versus TVOCs, respectively. These associations are still relatively weak, but statistically significant with relatively small p‐values of 0.0013 and 0.0001, respectively. For primary emissions, ceiling tile and painted gypsum wallboard did not show any significant association with environmental conditions, with p‐values greater than 0.1 for all combinations of environmental parameter and primary emissions. Primary emissions from activated carbon exhibited a weak but statistically significant association with field dustiness and temperature (R2 values of 0.33 and 0.32 respectively, p‐values of 0.016 and 0.017, respectively). Primary 108
emissions from carpet were also weakly associated with monthly total TVOC abundance and mean RH (R2 values of 0.43 and 0.26 respectively, p‐values of 0.010 and 0.045, respectively). For secondary emissions, activated carbon did not show any significant association with environmental parameters; p‐values were all above 0.05. However, carpet showed a relatively strong association (R2 = 0.55, p = 0.003) between secondary emissions and RH, with secondary emissions increasing with monthly average RH at field locations. Also, all three green building materials showed relatively strong associations between secondary emissions and total TVOC abundance in air at the field sites, with R2 values of 0.50, 0.65, 0.75, and p values of 0.0052, 0.0008 and 0.0001 for ceiling tile, painted gypsum wallboard and carpet, respectively. It is clear that an increase in TVOC concentration in field location air leads to higher secondary emissions during chamber tests. This might be due to carbonyls in air at field sites adsorbing to materials and desorbing during chamber tests, reactive gases, e.g., unsaturated organic compounds, adsorbing to materials at field sites and reacting with ozone during ozonation of small test chambers, or some combination of both of these processes. Additional research is warranted to further explore and understand this association, as it might be an important consideration with respect to application of specific materials in environments with high VOC concentrations in core building air. Figure 3‐23. Association graph for carpet by‐product emissions versus field air TVOC abundance. 109
3.6 Task 5: Large chamber assessment of materials 3.7 Large Chamber Experiments: Results Ozone deposition and by‐product yield results for large chamber experiments are presented in this section. Results are provided for all three test materials and chamber surfaces (background). 3.7.1 Ozone deposition Ozone deposition velocities to chamber surfaces (background removal) and each experimental material are summarized in Figure 3‐24. Background ozone deposition velocities corrected for area coverage were subtracted from the ozone deposition velocity for each experimental material. Background ozone deposition velocities to chamber walls were low, ranging from 0.01 m h‐1 (low mixing and 25% RH) to 0.33 m h‐1 (high mixing and 75% RH). Background removal displayed an overall increasing trend with increasing relative humidity and room mixing intensity. Carpet exhibited the highest deposition velocities, ranging from 5.5 m h‐1 to 7.4 m h‐1. This deposition velocity was consistent across similar mixing intensities, and also unaffected by changes in relative humidity. Stronger mixing intensities led to increases in the deposition velocity of the carpet at all relative humidity levels. Increasing from low to high mixing intensity resulted in increases of deposition velocity of 36%, 31%, and 32% at 25% RH, 50% RH and 75% RH, respectively. 110
Mixing Condition RH Figure 3‐24. Ozone deposition velocity to background chamber and experimental materials. “Low” refers to low mixing condition and “High” refers to high mixing condition. Error bars are larger of propagated instrument error or standard error of the ozone decay regression summed with the background error. Raw data are presented in Appendix LC1. 111
Ceiling tile was characterized by moderate ozone deposition velocities, ranging from 1.9 m h‐1 to 2.6 m h‐1. Deposition velocities for ceiling tile were also fairly consistent across relative humidity levels. Slight increases in deposition velocity of 13% and 26% were observed with increased mixing intensity at RH = 50% and 75%, respectively. However, at 25% RH deposition velocity decreased by 15% with the same increase in mixing intensity. Painted drywall exhibited low ozone deposition velocities, ranging from 0.20 m h‐1 to 0.65 m h‐1. The deposition velocity was effectively zero (same as background chamber walls) for 25% RH and high mixing intensity. Painted drywall showed a trend of decreased deposition velocity with increased mixing intensity. At 25% RH, the higher room mixing resulted in a decrease of ozone removal from 0.20 h‐1 to slightly less than 0 h‐1, while painted drywall at 50% RH and 75% RH resulted in decreases of 46% and 26%, respectively, with increases in mixing intensity. However, these variations are likely irrelevant given the consistently low absolute deposition velocities. 3.7.2
Primary Emissions 3.7.2.1 Light Aldehydes Primary emissions of light aldehydes from the three building materials and stainless steel chamber walls are summarized in Figure 3‐25. Patterns on each bar correspond with individual aldehydes. The legend and the order of specific aldehydes in the stacked bar graph are both in ascending order of molecular weight (e.g., C1 being the lowest molecular weight and at the bottom of the stacked bars and legend, and C4 being the highest molecular weight and at the top of the stacked bars and legend). Background primary emissions of light aldehydes were generally low, ranging from 2 µg m‐2 h‐1 to 19 µg m‐2 h‐1. Emissions were highest for 50% RH, decreasing with either decreasing or increasing RH. Mixing conditions had inconsistent effects on background primary emissions. Carpet exhibited higher primary emissions of light aldehydes than other test materials, mainly in the form of acetone (AT) and acetaldehyde (C2). Total primary light aldehyde emissions from carpet ranged from 9 µg m‐2 h‐1 (low mixing and 25% RH) to 82 µg m‐2 h‐1 (low mixing and 50% RH). Similar to background conditions, primary light aldehyde emissions from carpet were highest for the 50% RH condition, averaging 74 µg m‐2 h‐1 over both high and low mixing conditions. This average decreased to 61 µg m‐2 h‐1 at 75% RH and to 21 µg m‐2 h‐1 at 25% RH. Increases in room mixing intensity from 6 h‐1 to 12 h‐1 resulted in an increase in total light aldehyde emissions of 242% at 25% RH and 22% at 75% RH. However, total light aldehyde emissions decreased by 18% when mixing intensity increased at 50% RH. Ceiling tile exhibited moderate primary emissions of light aldehdyes, dominated by acetone, which contributed an average of 42% of total primary emissions. Total emissions from ceiling tile ranged from 3.7 µg m‐2 h‐1 (low mixing and 50% RH) to 34 µg m‐2 h‐1 (low mixing and 75% RH). Averaging across constant relative humidity resulted in minimum primary emissions at 50% RH. Mean emissions at 25% RH were 25 µg m‐2 h‐1 but decreased to 6.0 µg m‐2 h‐1 at 50% RH. The mean total light aldehyde emission rate at 75% RH was 23 µg m‐2 h‐1. For ceiling tile, an increase in room mixing intensity resulted in decreases in total light aldehyde emissions of 47% and 64% 112
for 25% RH and 75% RH, respectively, and increases of light aldehyde emissions of 117% for 50% RH. Painted drywall generally exhibited low primary emissions of light aldehydes. Total emissions from painted drywall ranged from 0 µg m‐2 h‐1 (both 25% conditions) to 36 µg m‐2 h‐1 (low mixing and 75% RH). Averaging across constant relative humidity resulted in increasing primary emissions with increases in RH. Emissions increased from 0 µg m‐2 h‐1 to 3.1 µg m‐2 h‐1 to 27.7 µg m‐2 h‐1 for RH = 25%, 50%, and 75%, respectively). Increases in room mixing intensity resulted in an increase (relative to low mixing intensity) of total light aldehyde emissions of 286% at 50% RH, and a decrease of 45% at 75% RH. 3.7.2.2 Heavy Aldehydes Primary emissions of heavy aldehydes from test materials and stainless steel chamber walls are summarized in Figure 3‐26. 113
Figure 3‐25. Primary emissions of light aldehydes from background chamber surfaces and test materials. “Low” refers to low mixing condition and “High” refers to high mixing condition. Raw data and uncertainties associated with these measurements are presented in Appendices LC1 and LC2, respectively. 114
Mixing RH Figure 3‐26. Primary emissions of heavy aldehydes from background chamber surfaces and test materials. “Low” refers to low mixing condition and “High” refers to high mixing condition. Raw data and uncertainties associated with these measurements are presented in Appendices LC1 and LC2, respectively. 115
Primary emissions of heavy aldehydes from chamber walls were generally low, ranging from 1.4 µg m‐2 h‐
1
to 12.5 µg m‐2 h‐1. Emissions appeared to decrease slightly with increases in mixing intensity and relative humidity, but these variations were small given absolute levels of background emissions. Carpet exhibited higher primary emissions of heavy aldehydes than other test materials, mainly in the form of nonanal (C9). Total primary emissions of heavy aldehydes from carpet ranged from 17 µg m‐2 h‐1 (low mixing and 25% RH) to 61 µg m‐2 h‐1 (high mixing and 25% RH). Primary emissions from carpet followed a trend of decreasing emissions with increasing relative humidity. Averaging across constant relative humidity, that is at high and low mixing for a specific RH, results in decreases of heavy aldehyde emissions from carpet from 39.1 µg m‐2 h‐1 to 35.3 µg m‐2 r‐1 to 24.3 µg m‐2 h‐1, at 25% RH, 50% RH and 75% RH, respectively. Increases in room mixing intensity from 6 h‐1 to 12 h‐1 resulted in an increase of total heavy aldehyde emissions of 240% at 25% RH, but decreases of total heavy aldehyde emissions of 30% and 21%, for 50% RH and 75% RH, respectively. Ceiling tile exhibited low primary emissions of heavy aldehdyes. Total emissions from ceiling tile were on the order of background emissions and ranged from 2.5 µg m‐2 h‐1 (high mixing and 25% RH) to 24.3 µg m‐2 h‐1 (low mixing and 75% RH). A slight increase in heavy aldehyde emissions occurred when averaging over constant RH from 4.7 µg m‐2 h‐1 (at 25% RH) to 7.0 µg m‐2 h‐1 (50% RH). However, this small increase is only slightly larger than the average error associated with measurements. At 75% RH the average total heavy aldehyde emission across mixing intensities was 14 µg m‐2 h‐1. This increase in emissions was entirely due to an increase in nonanal emissions. For ceiling tiles, increases in mixing intensity resulted in decreases of total heavy aldehyde emissions of 64%, 54%, and 87%, for 25% RH, 50% RH, and 75% RH, respectively. Painted drywall generally exhibited low primary emissions of heavy aldehydes. Total emissions from painted drywall ranged from 1.4 µg m‐2 h‐1 (high mixing and 50% RH) to 201 µg m‐2 h‐1 (low mixing and 75% RH). The large spike in emissions for the low mixing and 75% RH condition appears to be an unexplained outlier. Based on emission rates under other conditions for the painted drywall, this emission rate returns a modified z‐score greater than 3.5 (z‐score = 19.8) representing a statistical outlier. Excluding this data point results in no apparent primary emissions trend with increasing RH. For the painted drywall samples, increases in room mixing intensity resulted in decreases of total heavy aldehyde emissions of 53% and 96% at 25% RH and 50% RH, respectively. 3.7.3
Secondary Emissions 3.7.3.1 Light Aldehydes Secondary emissions of light aldehydes from the three building materials of interest and background chamber walls are summarized in Figure 3‐27. Background secondary emissions of light aldehydes were generally low, ranging from only 0.0 µg m‐2 h‐1 to 1.9 µg m‐2 h‐1. Carpet generally exhibited the highest secondary emission rates of light aldehydes, although all materials generally demonstrated low secondary formation. Total secondary emissions of light aldehydes from carpet ranged from only 0.4 µg m‐2 h‐1 (75% RH and low mixing) to 9.5 µg m‐2 h‐1 (25% RH and high mixing). Secondary emissions from carpet followed a trend of decreasing emission rate with increasing relative humidity. Averaging across constant relative humidity results in decreases of mean total light aldehyde emissions from carpet of 8.1 µg m‐2 h‐1 to 1.1 µg m‐2 h‐1 to 1.6 µg m‐2 h‐1, at 25% RH, 50% RH and 75% RH, respectively. Note that 1.1 and 1.6 µg m‐2 h‐1 are not statistically different. Conversely, increases in room mixing intensity resulted in increases of in secondary emissions of light aldehydes of 43%, 21%, and 593% at 25% RH, 50% RH and 75% RH, respectively. 116
Ceiling tile exhibited very low secondary emissions of light aldehydes. Only three experimental conditions resulted in increases in secondary emissions above background levels. Emissions of 0.9, 2.9 and 4.6 µg m‐2 h‐1 were observed for 25% RH and high mixing, 50% RH and low mixing, and 75% RH and low mixing, respectively. Painted drywall also exhibited very low secondary emissions of light aldehydes, with the exception of a spike of acetone of 19.1 µg m‐2 h‐1 during the 75% RH and high mixing condition. Apart from this peak, statistically significant emissions above background levels were noted for only two of six experimental conditions, both at 50% RH. Under this RH condition, secondary emissions of total light aldehydes of 3.5 µg m‐2 h‐1 (low mixing) and 5.8 µg m‐2 h‐1 (high mixing) were observed. 3.7.3.2 Heavy Aldehydes Secondary emissions of heavy aldehydes from the three building materials of interest and background chamber walls are summarized in Figure 3‐28. As with secondary light aldehydes, background secondary emissions of heavy aldehydes were generally low, ranging from 0.89 µg m‐2 h‐1 to 11 µg m‐2 h‐
1
. Background secondary emissions increased slightly with increases in mixing intensity. Increases in relative humidity caused slight decreases in background secondary emissions. Carpet had the highest secondary emission rates of heavy aldehydes. Similar to primary emissions, the greatest contributor to secondary emissions was nonanal. Total secondary heavy aldehyde emissions from carpet ranged from 61 µg m‐2 h‐1 (75% RH and low mixing) to 238 µg m‐2 h‐1 (25% RH and high mixing). As with primary emissions, secondary emissions from carpet followed a trend of decreasing emission rate with increasing relative humidity. Averaging across constant relative humidity results in decreases of mean total secondary emissions of heavy aldehyde from carpet of 211 µg m‐2 h‐1 to 193 µg m‐2 h‐1 to 77 µg m‐2 h‐1, at 25% RH, 50% RH and 75% RH, respectively. Conversely, increases in room mixing intensity resulted in increases of total secondary emissions of heavy aldehydes of 28.5%, 3.2%, and 55.1% at 25% RH, 50% RH and 75% RH, respectively. Ceiling tile exhibited very low secondary emissions of heavy aldehydes. Only two experimental conditions resulted in increases in secondary emissions above background levels. Emissions of 5.2 µg m‐2 h‐1 and 2.1 µg m‐2 h‐1 were observed for 50% RH and low mixing, and 75% RH and high mixing, respectively. Painted drywall also exhibited very low secondary emissions of heavy aldehydes. Emissions above background levels were noted for only two of six experimental conditions, both at 75% RH. Under this RH condition, secondary emissions of total heavy aldehydes of 5.4 µg m‐2 h‐1 (low mixing) and 16 µg m‐2 h‐1 (high mixing) were observed. 117
Figure 3‐27. Secondary emissions of light aldehydes from background chamber surfaces and test materials. “Low” refers to low mixing condition and “High” refers to high mixing condition. Raw data and uncertainties associated with these measurements are presented in Appendices LC1 and LC2, respectively. Mixing RH Figure 3‐28. Secondary emissions of heavy aldehydes from background chamber surfaces and experimental materials. “Low” refers to low mixing condition and “High” refers to high mixing condition. Raw data and uncertainties associated with these measurements are presented in Appendices LC1 and LC2, respectively. 118
3.7.4
Molar Yields 3.7.4.1 Light Aldehydes Molar yields (moles of by‐product produced per mole of ozone consumed) of light aldehydes from the three test materials and background chamber surfaces are presented in Figure 3‐29. Yields were greatest for the painted drywall, ranging from 0.001 to 0.33 for total light aldehydes for low mixing at 25% RH, and for high mixing at 75% RH, respectively . Yields for ceiling tile were nearly zero for all conditions studied, due to the absence of light aldehyde by‐products. Carpet exhibited minimal yields under the test conditions studied. Molar yields of aldehydes from background chamber surfaces appear elevated because of the small amount of molar consumption of ozone to chamber walls. 3.7.4.2 Heavy Aldehydes Molar yields of heavy aldehydes from the three test materials and background chamber surfaces are presented in Figure 3‐31. Yields were greatest for recycled carpet, and ranged from 0.11 to 0.28 for total heavy aldehydes for low mixing at 75% RH, and low mixing at 50% RH, respectively. Yields for ceiling tile were nearly zero for all test conditions. Painted drywall had minimal yields with the exception of nonanal for two test conditions. Nonanal yields of 0.18 and 0.08 were noted for high mixing at 25% RH and high mixing at 75% RH, respectively. Molar yields of heavy aldehydes from background chamber walls were elevated because eof the small amounts of ozone molar consumption to chamber walls. Figure 3‐29. Molar yields of light carbonyls for background chamber surfaces and test materials. “Low” refers to low mixing condition and “High” refers to high mixing condition. Raw data are presented in Appendix LC1. 119
Figure 3‐30. Molar yields of light carbonyls for background chamber surfaces and test materials. “Low” refers to low mixing condition and “High” refers to high mixing condition. Raw data are presented in Appendix LC1. 120
Figure 3‐31. Molar yields of heavy aldehydes for background chamber surfaces and test materials. “Low” refers to low mixing condition and “High” refers to high mixing condition. Raw data are presented in Appendix LC1. 121
3.8 Task 7: Field house experiments Results from experiments conducted in the UTest House include ozone removal rates and emissions of light and heavy aldehydes in a setting that approximates real‐world conditions. 3.8.1 Ozone deposition velocities Ozone deposition velocities to the background bedroom surfaces and ceiling tile are summarized in Figure 3‐32. Background ozone deposition velocity to the exposed surfaces of the bedroom is included in the ozone deposition velocity for the bedroom after installation of ceiling tile. Background ozone removal to bedroom surfaces was relatively high, ranging from 1.5 m h‐1 (fan on and steady‐state ozone) to 3.4 m h‐1 (fan off and steady‐state ozone). Background removal did not exhibit a clear or expected trend with increasing room mixing intensity. Ozone removal within the bedroom increased slightly after ceiling tile was installed during four of the six experiments. The two conditions for which the deposition velocity decreased relative to background were no fan at steady‐state and no fan at unsteady‐state. At high mixing intensity in the bedroom with ceiling tile, whole‐room ozone removal increased, ranging from 1.8 m h‐1 to 3.2 m h‐1. Ozone deposition velocities at high mixing intensity due to ceiling tile alone were significantly lower in comparison with deposition velocities measured for ceiling tile in the large chamber (2 m h‐1 to 2.6 m h‐1). 122
Figure 3‐32. Ozone deposition velocity to bedroom surfaces with and without ceiling tile and with no fan and fan in operation. SS refers to steady‐state conditions.
123
3.8.2
Emissions 3.8.2.1 Light Aldehydes Emissions of light aldehydes from the background bedroom surfaces and from the ceiling tile are summarized in Figure 3‐33. Patterns on each bar correspond with individual aldehyde emission rates. Background total emissions of light aldehydes were generally low, ranging from 108 µg h‐1 to 1100 µg h‐1 (1.7 µg m‐2 h‐1 to 17 µg m‐2 h‐1). Emissions were primarily in the form of formaldehyde (C1) and acetaldehyde (C2). Emissions were highest for the higher mixing intensity conditions. Total light aldehyde emissions increased slightly after ceiling tile was installed for five of the six conditions, ranging from 300 µg h‐1 to 545 µg h‐1. The largest increase in emissions after installation of ceiling tile was from 108 µg h‐1 to 268 µg h‐1 (149% increase), corresponding with the no fan, steady‐state ozone (SS1) condition. However, for the fan on, steady‐state ozone (SS1) condition, the whole‐room total aldehyde emissions decreased from 1109 µg h‐1 to 294 µg h‐1 (73% decrease). Average total light aldehyde emissions attributed to ceiling tile alone during steady‐state ozone conditions were 31 µg m‐2 h‐1, slightly higher than the average emissions observed in the large chamber. 3.8.2.2 Heavy Aldehydes Emissions of heavy aldehydes from the background bedroom surfaces and from the ceiling tile are summarized in Figure 3‐34. Background total emissions of heavy aldehydes were relatively high, ranging from 1240 µg h‐1 to 7500 µg h‐1 (19 µg m‐2 h‐1 to 119 µg m‐2 h‐1). Background emissions of heavy aldehydes were dominated by hexanal (C6). Greater background total emissions were observed during the higher mixing intensity conditions. Total heavy aldehyde emissions decreased after ceiling tile was installed on all four days that no ozone was injected into the bedroom (SS1 & SS3). On the two days when ozone was injected into the bedroom, the total heavy aldehyde whole‐room emissions increased by 40% and 20% on low and high mixing intensity days, respectively. During all steady‐state ozone conditions after ceiling tile was installed, average total heavy aldehyde emissions decreased by 177 µg m‐2 h‐1 (61% decrease). 124
Figure 3‐33. Light aldehyde emission rates in bedroom with and without ceiling tile. BG refers to background (without ceiling tile) and CT refers to room conditions after ceiling tile was added. 125
Figure 3‐34. Heavy aldehyde emission rates in room with and without ceiling tile. BG refers to background (without ceiling tile) and CT refers to room conditions after ceiling tile was added. 126
3.8.3
Molar Yields 3.8.3.1 Light Aldehydes Molar yields of light aldehydes from the background bedroom surfaces and from the ceiling tile are shown in Figure 3‐35. Yields in Figure 3‐35 were obtained only from the four ozone decay experiments. Background yields of light aldehydes ranged from 0.044 to 0.079, which fall within the range of background yields observed for large chamber experiments (Section X). Yields increased above bedroom background levels after ceiling tile was installed, ranging from 0.087 to 0.135 (10% and 207%) on the high and low mixing intensity days, respectively. Total light aldehyde yields attributed to ceiling tile alone were 0.095 and 0.016 on the low and high mixing intensity days, respectively. The light aldehyde yields observed from ceiling tile in the test house were greater than observed in large chamber experiments. Yields were comparatively more significant during high mixing intensity studies for both the large chamber and test house experiments. 3.8.3.2 Heavy Aldehydes Molar yields of heavy aldehydes from the background bedroom surfaces and from the ceiling tile during ozone decay conditions are shown in Figure 3‐36. Background yields of heavy aldehydes ranged from 0.144 to 0.415, which are greater than the average combined primary and secondary background yields observed for large chamber experiments. After installation of ceiling tile, heavy aldehyde yields increased above bedroom background levels to 0.532 for the low mixing intensity condition, and decreased to 0.130 for the high mixing intensity condition. The total heavy aldehyde yield attributed to ceiling tile alone for the low mixing condition was 0.403, which is greater than all yields observed in large chamber experiments. The trend of decreasing molar yields with decreasing mixing intensity was not observed for the heavy aldehydes in the test house; however these results might be explained by the measured ozone deposition velocities for each condition. For the low mixing intensity condition, the background deposition velocity was 50% greater than the deposition velocity measured after installation of ceiling tile, which translates to a lower molar yield for the former condition relative to the latter condition. Conversely, for the high mixing intensity condition, the background ozone deposition velocity was 28% lower than the deposition velocity measured after installation of ceiling tile. As such, the background condition should have a higher molar yield than the condition with ceiling tile, provided that the emissions for each condition are similar. 127
Figure 3‐35. Light aldehyde molar yields for background room surfaces and to the room after ceiling tile was installed. Figure 3‐36. Heavy aldehyde molar yields for background room surfaces and to the room after ceiling tile was installed. 128
3.9 Criteria for possible LEED credit and test method (Grade development) 3.9.1 Impact on specific building A measurable goal for the interior of the building (concentration or otherwise) allows the standard setting to be health based. For example, a maximum indoor ozone concentration goal might be 20 parts per billion (ppb). This concentration is under consideration by Health Canada for residences (Lloyd, 2009). This value was chosen as a compromise between the reference concentration of 4 ppb (10% of the NOAEL derived from human studies (Adams, 2002)) and what is anticipated to be achievable in homes based on measurements in Canadian homes (Liu et al., 1995). An explicit concentration value is applied because “concentration” can be directly connected to health outcomes by way of human exposure or inhalation intake. Other metrics might be used that ultimately lead to the same result. 3.9.2
Application of a specified limit concentration: ozone Consider equation 2‐1 in a slightly different form: 1
C = Co
1+
⎫
1⎧
⎨∑ vd ,i Ai ⎬
Q⎩ i
⎭ Equation 3‐1 The average indoor concentration C depends on the outdoor concentration, Co, the infiltration or ventilation rate, Q, laboratory measured/reported values of material deposition velocities, vd,I, and the installed area, Ai, of all materials that contribute to the occupied areas of the building. The outdoor concentration Co could be chosen to correspond to a reasonable “maximum” value associated with the city in which the building is sited. In keeping with EPA methods for determining compliance with the Clean Air Act, the “4th highest 8‐hour average” outdoor concentration could be chosen. Note that this is somewhat arbitrary, but results in a very conservative outcome. In other words, the building would meet the design limit concentration for all but three 8‐hour periods during a year, or 99.7% of the time. For context, the 4th highest ozone concentration for individual monitors located in several metropolitan areas in 2009 are shown in Table 3‐2 (AirNow, EPA). Architects would have to ensure that the full complement of exposed materials (characterized by vdi and Ai) met the limit concentration requirement, and each region would have its own requirement. 129
Table 3‐2. 4th Highest 8‐hour average ozone concentration, C/Co and CADR /Q for various metropolitan areas. City/Region Monitor ID Houston (Harris county) Dallas Los Angeles Washington DC Chicago St. Louis Atlanta Seattle 4820100294420102
4808500054420101
0603700164420101
1100100254420101
1703100424420102
2900300014420101 1306700034420101 5301100114420101
4th highest ozone (ppb) C/Co for 20 ppb limit concentration 112 91
141
87
86
73
89
74
0.18 0.22
0.14
0.23
0.23
0.27
0.22
0.27
CADR/Q for 20 ppb limit concentration 4.6 3.6
6.1
3.4
3.3
2.7
3.5
2.7
If 20 ppb is the indoor limit concentration (arbitrary for this report), then the ratio C/Co can be specified ⎧
∑v
⎩
for each region. Note that the “clean air delivery rate” (CADR = ⎨
d ,i
i
⎫
Ai ⎬ ) divided by the ventilation ⎭
rate (Q) is now also uniquely determined. A building going up in Los Angeles would be held to a more stringent standard in any case than one in Seattle, requiring the architect or designer to specify more materials that remove ozone more effectively. Rather than a region‐based standard, we can use Table 3‐2 as a guide for specifying values that are reasonably protective for most regions, but allow all designers to use the same target values of C/Co or CADR/Q. Simply setting C/C0 = 0.2 or CADR/Q = 4, would be acceptably “protective” for all but Los Angeles and Houston. Since using the 4th highest 8‐hour average value as the metric is very conservative to begin with, indoor concentrations of ozone would still be below 20 ppb most of the time in Los Angeles and Houston. Refining further for commercial buildings is not directly possible since the ventilation rate depends on the size of the building and usage and would be unique to each building. However, by recognizing that ventilation rate scales with the building size, it may be possible to choose a typical air exchange rate for commercial buildings (λ=Q/V where V= building volume) and rewrite CADR/Q as CADR / Q =
1
∑v
λ
d ,i
i
Ai
V Equation 3‐2 In this new formulation, the area‐to‐volume ratio (Ai/V) appears. For many material types that go into buildings, the area‐to‐volume ratio may be rather uniform and more easily applied than direct use of the area. For example, the area‐to‐volume ratio for flooring (or ceilings) is roughly equal to 0.3‐0.4 m2/m3 for most buildings. Depending on the building use type, ASHRAE Standard 62.1 requires between 1‐2 L/s/m2 ventilation. For standard ~2.5‐3 m floors, this is equivalent to λ= 1‐ 3 air changes per hour. 130
Choosing λ=2 h‐1 and applying CADR/Q=4, the resulting sum of all surface removal “rates”, ⎧
Ai ⎫
‐1
⎬ = 8 h . ⎨∑ vd ,i
V ⎭
⎩ i
Residential materials specification may also be further refined by applying LEED IEQ 4.1 ( Meets ASHRAE 62.2 for mechanical ventilation) and/or LEED EA 3.1 (Air infiltration). ASHRAE 62.2 requires mechanical ventilation to deliver outdoor air at 1 cfm/100 ft2 of occupiable space plus 7.5 cfm per occupant. For a 2000 ft2 home with 2 occupants, this is equivalent to mechanically delivered air exchange rate = 0.65 h‐1. LEED EA 3.1 (an energy conservation measure) requires that infiltration result in an air exchange rate </= 0.35 h‐1 with more credits allowed for leakage rates as low as 0.15 h‐1. Assuming that an actively ventilated house is designed to have λ = 0.65 h‐1 and a passive house λ = 0.35 h‐1, the design values for ⎧
∑v
⎩
the overall removal rate, ⎨
i
d ,i
Ai ⎫
‐1
‐1
⎬ , range from 2.6 h to 1.4 h to meet a concentration ratio, C/Co V ⎭
= 0.2. Many buildings may already meet the required ozone removal. For example, in Table 2 of the review of indoor ozone concentrations (Weschler, 2000), several buildings and averages for sets of buildings had C/Co values equal to or less than 0.2. Modern or weatherized homes are anticipated to have low air exchange rates and are likely to experience C/Co < 0.2. However, the majority of non‐residential buildings (without activated carbon filtration) reported by Weschler had C/Co values >0.2. Therefore, most of these buildings do not presently exhibit sufficient ozone removal rates relative to their air exchange rates. 3.9.3 Application of a specified limit concentration: ozone reaction products Even if existing materials in a building are reactive enough to remove ozone effectively, they can impair air quality by the secondary emission of ORPs. This section discusses the next component of the overall metric required to both reduce ozone and ORP concentrations in buildings. Setting a specific indoor concentration limit for ORPs is likely to be more difficult than for ozone. Setting health based standards for every potential reaction product would be not be possible. In part this is due to the uncertainty in the measurement itself: as implemented in this project, only a narrow type of carbonyl (C1‐C12) compound was quantified. These act as a good indicator of surfaces that generate ORPs in general, but do not necessarily predict what other kinds of products may be generated. It is anticipated that materials generating hexanal, for example, will also generate some hexanoic acid (based on the chemical mechanism taking place), but yields of hexanoic acid are not immediately predictable. Further, it is difficult to determine from existing measurements if other compounds, such as unsaturated carbonyls, dicarbonyls and aerosols , would be generated at all. A second barrier to setting concentration limits is that little chronic toxicological or epidemiological data exist at the ppb or sub‐ppb concentrations that occur in buildlings, which would allow for determining “No Observable Adverse Effect Levels” or NOAELs. The term Healthy can refer to many desired outcomes: no increased probability of cancer, asthma, or death; no significant increase in irritancy or odor; no increased incidence of Sick Building Syndrome; no significant decrement in worker productivity. 131
For the purposes of demonstrating the method of grading materials based on an ORP concentration limit, we will use the total molar yield (y in the following discussion will represent summed molar yield (total) for all aldehydes from a specific material) derived from materials testing to calculate what the incremental increase in C1‐C12 carbonyl compounds would be in a building. We then set this to a reasonable level (X ppb) that is likely to protect most occupants from sensory effects; this assumes that other health effects become apparent at concentrations well above those that result in sensory effects. A notable exception to this assumption is formaldehyde, which is a known carcinogen and controlled at concentrations well below its odor or irritancy threshold. Sensory effects of carbonyl compounds and concomitant carboxylic acids. The following figure is extracted from Cometto‐Muniz et al. (1998) and demonstrates some key characteristics of aldehydes and carboxylic acids relevant to human sensory perception. Carboxylic acids tend to have thresholds (odor or pungency) roughly 100 times lower than the corresponding (same number of carbons) aliphatic aldehyde. The most abundant aldehyde generated in materials testing for this project was nonanal. Note that this was not tested by Cometto‐Muniz et al., but that its odor threshold will be ~1ppb by extrapolation. The threshold for nonanoic acid would likely be of the order 0.01 ppb. Lower molecular weight aldehydes have higher thresholds, but were observed, generally at lower secondary emission rates in our experiments. It is not presently clear how to relate the molar yield of a measured compound (e.g. nonanal) with that of a suspected ORP (e.g. nonanoic acid). Theoretically, there should be a ~ 1:1 relationship based on the chemical mechanism (Morrison and Nazaroff, 2002), but acidity conditions on the surface can shift this balance in either direction. Further, acids adsorb strongly to surfaces (original material, other materials or even airborne particles) and even if nonanoic acid is generated by this chemistry, it may not effectively be released into indoor air. By setting the incremental increase in all measured ORPs to a value that is protective for nonanal, we are probably being overly protective of lower molecular weight aldehydes, but underprotective of carboxylic acids or other unknown products. By using the odor threshold as a metric, rather than pungency, we are ensuring that carboxylic acids are unlikely to exceed pungency levels (but may still exceed odor thresholds). For demonstration purposes, we then set ΔCp = 1 ppb, and recognize that this value and its justification must be reviewed by an independent committee in the future. 132
Figure 3‐37. Odor and nasal pungency thresholds, reproduced from (Cometto‐Muñiz et al., 1998) The incremental increase in reaction product concentrations, on a molar basis is given by a simplified form of equation 2‐3, where all materials contribute to ORP production. ΔC p =
1⎧
⎨∑ yi vd ,i Ai
Q⎩ i
⎫
⎬C
⎭ Equation 3‐3 Recall that C is the concentration of ozone (ppb) in the building. Applying the 20 ppb “standard” for indoor ozone discussed earlier, ⎫
1⎧
⎨∑ yi vd ,i Ai ⎬ ≤ 0.05
Q⎩ i
⎭
Equation 3‐4 133
As above, this can be further refined to, 1⎧
Ai ⎫
⎬ ≤ 0.05
⎨∑ yi vd ,i
λ⎩ i
V ⎭
Equation 3‐5 ⎧
Ai ⎫
⎬≤
⎨∑ yi vd ,i
V ⎭ 0.1 h‐1 for commercial, 0.033 h‐1 for And using the typical air exchange rates, ⎩ i
mechanically ventilated residence and 0.018 h‐1 for a passive residence. Using the same parameters and assumptions developed so far, another metric can be applied that is nearly uniform across all building types. The area weighted total yield for a building is given by, ∑yv
Ai
V
= 0.013
Ai
V
i d ,i
i
∑v
d ,i
i
Equation 3‐6 This value applies to all building types because differences amongst buildings (air exchange rate) is normalized away. 3.9.4 Grading single materials: ozone In sections 3.8.2‐3, it was assumed that materials had been tested, for the parameters vd,i and yi, but these materials had not necessarily been certified for use in green buildings. It may be valuable to provide certifications for individual materials that, if installed at typical A/V rates, are likely to sufficiently protect building occupants from ozone and ORPs. Flooring, ceiling treatments and wall coverings/coatings all contribute high projected surface areas (or A/V) to indoor spaces. Therefore, carpets, linoleum, paint, wall paper, ceiling tiles and cubical dividers could all be suitably ranked/rated for a “single material” grade. It would probably not be useful to rank filing cabinets, computer monitors or other incidental materials unless the building is unusual (admittedly, these may “add up” but the focus of this section is on single material grading). Returning to the removal rate defined in section 3.9.2, a single material removal rate is given by, vd
A
V 134
Equation 3‐7 Recall that the sum over all materials should be 8 h‐1 or more for a commercial building. However individual materials should not be held up to this standard, since multiple materials will be used in the building to remove ozone. Instead, the fractional coverage of materials should be considered. Each building will have a different A/V depending on its design. But for a typical 2.5 m ceiling height, A/V for ceilings and floors = 0.4 m‐1. A/V for walls depend on room sizes, but taking a 3 X 4 m office as typical, the wall A/V would be 1.2. Taking each proportionally, ⎛ A⎞
−1
⎜ v d ⎟ = 4 .8 h
For a wall based material: ⎝ V ⎠
⎛ A⎞
−1
⎜ v d ⎟ = 1 .6 h V
⎠
For a ceiling‐only or floor‐only based material: ⎝
Although a somewhat simplistic analysis, we believe that a more nuanced approach, accounting for detailed dimensions of the building, will not provide a significantly more useful metric. Residential dimensions are not substantially different, and it is reasonable to use these preliminary area‐
to‐volume ratios for those settings as well. For mechanically ventilated residences, the removal rates would be 1.5 and 0.5 h‐1 for wall‐based and ceiling/floor based materials respectively. For passively ventilated residences, the removal rates would be 0.3 and 0.9 h‐1 respectively. Averaging over all surfaces, and for the sake of simplicity, the value could be set at 2‐3 h‐1 for all materials. This over protects in residential settings, but should be sufficient in commercial buildings. While the deposition velocity, vd, alone is not sufficient alone to grade a material for its resulting impact on an indoor environment, it is notable that the deposition velocity is also equal to the clean air delivery rate per unit installed area, CADR/A. Since CADR is commonly used to rate air cleaners, use of this metric may be more familiar to some architects or designers. 3.9.5 Grading single materials: ORPs To grade single materials, we can apply the results for multiple materials. Assuming that all major materials installed all meet the criteria, 1
λ
yvd
A
≤ 0.05
V
Equation 3‐8 135
And identical results for multiple materials can be applied to specific buildings. The removal rate parameter, yvd
A
≤
V Equation 3‐9 0.1 h‐1 for commercial, 0.033 h‐1 for mechanically ventilated residence and 0.018 h‐1 for a passive residence. Further, simplification for equation 3‐9 demonstrates that the yield for an individual material should be y < 0.013 regardless of the building type. We suspect that this may be close to or below the ability of some testing labs to measure the total yield. In that case, a suitable lower limit of quantification can be set as the cut –off value for certification. 136
3.9.6 Overview of parameters and metrics Table 3‐3 is a compilation of recommended parameters that could be used for rating materials or interior designs for achieving LEED credits. This table does not include the possibility that certification would be based on regional differences in outdoor ozone concentrations. Table 3‐3. Parameters and limit values for rating materials for ozone control capabilities and byproduct prevention Metric Indoor/outdoor ozone ratio CADR/Q Summed surface removal rates ORP formation limit Equation 1
⎫
1⎧
1 + ⎨∑ vd ,i Ai ⎬
Q⎩ i
⎭
1
1
A
vd ,i Ai = ∑ vd ,i i
∑
Q i
λ i
V
A
∑i vd ,i Vi Residential (Passive Ventilation) 0.2 4 8 2.6 1.4 ORP emissions, whole building oriented ⎫
1⎧
⎨∑ yi vd ,i Ai ⎬
Q⎩ i
⎭
1⎧
Ai ⎫
= ⎨∑ yi vd ,i
⎬
λ⎩ i
V ⎭
⎧
Ai
⎨∑ yi vd ,i
V
⎩ i
Weighted total Ai
yield for building ∑ yi vd ,i V
i
A
∑i vd ,i Vi
<0.05 ⎫
⎬ ⎭
‐1
0.1 h
‐1
0.018 h‐1
0.033 h
0.013 Ozone removal, individual material oriented vd
A
V (wall, ceiling or floor)
4.8, 1.6 h‐1 1.5, 0.5 h‐1 0.9, 0.3 h‐1 ORP emissions, individual material oriented 1
λ
yvd
A
V
A
yv d V
y Residential (Mechanical Ventilation) Ozone removal, whole building oriented C
=
Co
ORP relative formation “rate” Ozone removal rate Commercial 0.05 ‐1
0.1 h
‐1
0.033 h
0.013 137
0.018 h‐1
3.9.7 Application of parameters and metrics to materials tested Here we use the small chamber results to rank the materials using the metrics outlined in the previous section. For clarity, we will not attempt to design a green building to use the “whole building” metrics. Instead, the individual materials will be ranked based on commercial building metrics. Only one material (bolded) meets the requirements shown in Table 3‐4, WCP‐1, the clay wall plaster. However, noting that such a low yield may be below the limit of quantification for some commercial chambers (and we observed this first hand), a more liberal value of vd(A/V)y = 0.3 may be appropriate. In this case, three other materials meet the requirements (italicized) using S&T results. However, applying yield values from the UT chamber, the carpet FC‐1 would not meet this metric. Fabric wall WC‐3 is borderline. Table 3‐4. Metrics applied to 19 materials tested in 10 L chamber ID description vd (m h‐1) y
vd
A
V yv d
(h‐1)
A
V (h‐1) FC‐1 FC‐2 FRf‐1 FRf‐2 FRf‐3 FCf‐1 FWf‐1 FWf‐2 WC‐1 WC‐2 WC‐3 WP‐1 WP‐2 WP‐3 WCP‐1 WD‐1 CP‐1 CP‐2 CP‐3 Floors recycled carpet fabric backed carpet bio‐based resilient tile puzzle‐locking tiles bio‐based resilient tiles porcelain clay tile finished hardwood floor finished bamboo floor Wall coverings/coatings cork wall tiles fabric acoustical wall panel fabric wall covering latex paint and primer clay based paint collagen based paint clay plaster wall coating recycled drywall Ceiling materials mineral fiber ceiling tile perlite ceiling tile fiberglass ceiling tile 4.9
3.9
0.4
1.7
0.3
0.3
0.7
0.5
0.11
0.17
0.11
0.08
0.32
0.18
0.40
0.05
2.0
1.6
0.1
0.7
0.1
0.1
0.3
0.2
0.21 0.26 0.02 0.06 0.04 0.02 0.11 0.01 0.7
6.3
1.3
0.7
7.5
0.9
4.6
6.5
0.04
0.48
0.02
0.03
0.18
0.00
0.00
0.04
0.9
7.6
1.5
0.9
9.0
1.0
5.5
7.7
0.03 3.61 0.03 0.03 1.60 0.00 0.00 0.33 6.8
2.1
6.2
0.10
0.03
0.08
2.7
0.8
2.5
0.26 0.02 0.20 Shown in Figure 3‐38 is a graphical representation of the metrics and materials tested. Two boxes (for two different limits on vd(A/V)y) surround results for several materials, depending on their type (floor/ceiling or walls). Arrows indicate that two materials had very high values of vd(A/V)y and are not shown on the chart. 138
Floor and ceilng materials
Wall coverings
and coatings
0.50
0.40
yield*removal rate, vd(A/V)y
yield*removal rate, vd(A/V)y
0.50
0.3 limit
0.30
CP‐1
FC‐1
0.20
CP‐3
0.10
0.40
WD‐1
0.3 limit
0.30
0.20
0.10
0.1 limit
0.1 limit
WCP‐1
0.00
0.00
0.0
0.5
1.0
1.5
2.0
2.5
3.0
0.0
removal rate (vd(A/V))
2.0
4.0
6.0
8.0
removal rate (vd(A/V))
Figure 3‐38. Graphical representation of how tested building materials compare against metrics for meeting proposed ozone control and byproduct prevention criteria. 139
4 Conclusions and recommendations 4.1 Conclusions 4.1.1 Materials tested Building materials tested covered a cross‐section of materials available including flooring, ceilings and wall coverings. But the selection was necessarily “skeletal” in scope due to limited resources. The total number of materials considered green by various metrics is orders of magnitude larger than the total number tested in this project. Even for a single product line of a single manufacturer, there may be tens to hundreds of specific styles. Therefore, conclusions drawn about the type of material cannot be extrapolated very far. However, in combination with information about the materials themselves and other evidence, some broad conclusions can be drawn. In general, porous materials composed mostly of inorganic substances appear to have the desirable property of exhibiting moderate to high ozone deposition velocities, but lower byproduct yields. In this project, those materials included clay wall plaster, unpainted drywall and ceiling tiles. This is consistent with observations that concrete, brick and other similar materials exhibit high ozone removal rates (Grøntoft and Raychaudhuri, 2004). However, most prior research did not measure secondary emission rates. But given the composition, it is unlikely that ozone reactions with these materials will generate substantial amounts of organic byproducts unless they are coated with reactive organic materials. Fleecy textile materials react readily with ozone and generate modest and sometimes substantial secondary emission rates of byproducts. This has been observed for carpet(Morrison and Nazaroff, 2002) and has been attributed to oils used in the manufacture of textiles (spinning oils). It is unlikely that green characteristics such as “recycled” or “sustainable” have much impact on this. Low porosity, smooth flooring materials with a glaze or hard coating tend to exhibit low ozone deposition velocities. This is likely due to the combination of characteristics. Low surface area reduces reactive site density on the surface. Unreactive glazes and polymer coatings further reduce reactivity, even for materials that are anticipated to be somewhat reactive with ozone (e.g. wood). Two of the paints also exhibited low reactivity with ozone as has been observed in prior research (Reiss et al., 1995; Wang and Morrison, 2006). But a clay‐based paint had the highest deposition velocity measured, but also generated a large amount of carbonyl compounds as byproducts. The ingredient list did not shed light on the reason for this, but some “drying oils” may have been present that are known to react with ozone. These drying oils are not generally present in modern water‐based latex paints. Several materials were included because they were “bio‐based” or included organic materials expected to react readily with ozone, and perhaps contribute substantially to byproduct emissions. However, the results are mixed. The collagen based paint and the two bio‐based resilient floor tiles were not highly reactive, although the tiles did generate byproducts with moderate to high yields. The clay based paint 140
did not look, based on the ingredient list, to fit into the category of “bio‐based”, but clearly was very reactive and probably included bio‐based oils. All of these materials are expected to be installed such that they contribute to most of the surface area available in buildings. These are anticipated to strongly influence the composition of air (for better or worse). 4.1.2 Test method and rating metrics The chamber test method appears to adequately and reproducibly measure ozone removal in the form of the deposition velocity. Measurements in three different chambers differ somewhat, probably due to difference in air exchange rate. The results for the 10 L (high air exchange rate) matches full scale results at the lower air mixing rates in the 68 m3 UT chamber. Choice of temperature or relative humidity do not significantly influence results of ozone uptake in either small chamber or at full scale. However, the chamber ozone concentration does influence the deposition velocity. Byproduct emission rates and yields were more difficult to reproduce and quantify in the small 10 L chamber, but were more reproducible in the larger UT chambers. This may have less to do with the chamber itself than with the conditions within the laboratory itself that could result in contamination before testing. Small chamber experiments did not indicate a significant influence of temperature, relative humidity or ozone concentration on byproduct emission rates. However, in full scale testing we observed that higher relative humidity resulted in lower byproduct emission rates. The metrics recommended for rating materials, and for potentially developing a point system similar to those already established for Indoor Environmental Quality, are based on the anticipated impact of these materials on indoor environments. Our preliminary tests in an instrumented “test house” were promising but somewhat inconclusive. Ozone removal rates did not appear to be significantly increased with the addition of perlite‐based ceiling tiles. This is likely due to the relatively high background reactivity of the room. However, the ceiling tiles did appear to reduce the secondary emission rates of carbonyl compounds in some cases, likely by reducing the total ozone flux to other surfaces. 4.2 Recommendations 4.2.1 Target building materials for testing With a bit more testing, it may be established that materials composed of inorganic material, that are fairly porous, and that do not include substantial amounts of reactive organic binders or oils, are likely to be good candidate for by‐product free ozone removal in buildings. Given that the test method is likely to be somewhat more expensive and time consuming than existing emission testing methods, manufacturers may want to be selective in the materials that they want rated by this method. 4.2.2 Test methods and extrapolation Small chambers of at least 10 L in volume, operated at 25 C and 50% RH with an internal ozone concentration in the 50‐100 ppb range should adequately generate reliable deposition velocity values that can be extrapolated to real‐world settings. To ensure that byproduct emission rates are reliable, we may have a bit more work ahead of us. It is clear that the 48L chamber worked well, but at this point we 141
don’t know precisely why. Given the potential impact of relative humidity, we recommend that the condition of 50% relative humidity be adhered to in commercial labs. Further testing in buildings, including testing multiple materials in various combinations, is prudent to demonstrate that the predicted impacts result in real‐world improvements. 4.2.3 LEED point(s) and metrics The metrics recommended are based on the anticipated impact of the materials on indoor environments. It is necessary to account for installed area of the material, air exchange rates and potentially other building characteristics. However, we believe that the simplest metrics, that provide a margin of safety, are probably the most likely to be adopted. It is not possible to reduce the metric to fewer than two parameters, since the impact on ozone and the byproducts require consideration of two independent physical/chemical parameters of the building material. If a single value is used to represent the ozone removal rate (vd(A/V)), we recommend 2‐3 h‐1. This may be over protective for residences, but adequate for commercial buildings. The yield parameter (vd(A/V)y) will depend on the ability of commercial labs to quantify the yield with some precision. Although we would like to see this parameter be set to < 0.1, it may be more practical to choose a larger value, but the actual value will, again, depend on laboratory capabilities. 142
5 References Adams, W. C., 2002. Comparison of chamber and face‐mask 6.6‐hour exposures to ozone on pulmonary function and symptoms responses. Inhalation Toxicology 14(7), 745‐764 Bekö, G., Halás, O., Clausen, G., Weschler, C. J., 2006. Initial studies of oxidation processes on filter surfaces and their impact on perceived air quality. Indoor Air 16, 56‐64 Bell, M. L., Peng, R. D., Dominici, F., 2006. The exposure‐response curve for ozone and risk of mortality and the adequacy of current ozone regulations. Environmental Health Perspectives 114(4), 532‐536 Calogirou, A., Larsen, B. R., Brussol, C., Duane, M., Kotzias, D., 1996. Decomposition of terpenes by ozone during sampling on tenax. Analytical Chemistry 68(9), 1499‐1506 Census, U. S. B. o., 2005.American housing survey. Washington, D.C. Clausen, P. A., Wolkoff, P., 1997. Degradation products of tenax ta formed during sampling and thermal desorption analysis: Indicators of reactive species indoors. Atmospheric Environment 31(5), 715‐725 Cometto‐Muñiz, J. E., Cain, W. S., Abraham, M. H., 1998. Nasal pungency and odor of homologous aldehydes and carboxylic acids. Experimental Brain Research 118, 180‐188 Grøntoft, T., Raychaudhuri, M. R., 2004. Compilation of tables of surface deposition velocities for o3, no2 and so2 to a range of indoor surfaces. Atmospheric Environment 38, 533‐544 Hyttinen, M., Pasanen, P., Kalliokoski, P., 2006. Removal of ozone on clean, dusty, and sooty supply air filters. Atmospheric Environment 40, 315‐325 Kleindienst, T. E., Corse, E. W., Blanchard, F. T., Lonneman, W. A., 1998. Evaluation of the performance of dnph‐coated silica gel and c18 cartridges in the measurement of formaldehyde in the presence and absence of ozone. Environmental Science & Technology 32(1), 124‐130 Kleno, J., Clausen, P. A., Weschler, C. J., Wolkoff, P., 2001. Determination of ozone removal rates by selected building products using the flec emission cell. Environment Science and Technology 35(12), 2548‐2553 Kunkel, D. A., Corsi, R. L., Novolselec, A., Siegel, J. A., Morrison, G. C., 2008. Passive ozone control through use of reactive indoor wall and ceiling materials. Air and Waste Management Annual Conference and Exposition, Portland, OR. Liu, L. J. S., Koutrakis, P., Leech, J., Broder, I., 1995. Assessment of ozone exposures in the greater metropolitan toronto area. Journal of the Air and Waste Management Association 45(4), 223‐234 143
Lloyd, K., 2009. Proposed residential indoor air quality guideline for ozone. Canada Gazette 143(14) Morrison, G. C., Corsi, R. L., Destaillats, H., Nazaroff, W. W., Wells, J. R., 2006. Indoor chemistry: Materials, ventilation systems, and occupant activities. Healthy Buildings 2006, Lisbon, Portugal. Morrison, G. C., Nazaroff, W. W., 2002. Ozone interactions with carpet: Secondary emissions of aldehydes. Environmental Science & Technology 36(10), 2185‐2192 Morrison, G. C., Nazaroff, W. W., Cano‐Ruiz, J. A., Hodgson, A. T., Modera, M. P., 1998. Indoor air quality impacts of ventilation ducts: Ozone removal and emissions of volatile organic compounds. Journal of the Air and Waste Management Association 48(10), 941‐952 Pellizzari, E., Demian, B., 1984. Sampling of organic compounds in the presence of reactive inorganic gases with tenax gc. Analytical Chemistry 56, 793‐798 Poppendieck, D., Hubbard, H. F., Ward, M., Corsi, R. L., 2007. Formation and emissions of carbonyls during and following gas‐phase ozonation of indoor materials. Atmospheric Environment 41, 7614‐7626 Poppendieck, D., Hubbard, H. F., Ward, M., Weschler, C. J., Corsi, R. L., 2007. Ozone reactions with indoor materials during building disinfection. Atmospheric Environment 41, 3166‐3176 Reiss, R., Ryan, P., Koutrakis, P., Tibbetts, S., 1995. Ozone reactive chemistry on interior latex paint. Environmental Science & Technology 29(8), 1906‐1912 Sadowska, J., Johansson, B., Johannessen, E., Friman, R., Broniarz‐Press, L., Rosenholm, J. B., 2008. Characterization of ozonated vegetable oils by spectroscopic and chromatographic methods. Chemistry and Physics of Lipids 151, 85‐91 U.S.E.P.A. 1999. Compendium of methods for the determiinatoin of toxic organic compounds in ambient air. Washington, D.C., Office of Research and Development, Center for Environmental Research Information. Wang, H., Morrison, G. C., 2006. Ozone initiated secondary emission rates of aldehydes from indoor surfaces in four homes. Environmental Science & Technology(40), 5263‐5268 Wang, H., Springs, M., Morrison, G. C., 2005. Ozone initiated secondary emissions of aldehydes from indoor surfaces. Air and Waste Management Association 2005 Meeting, Minneapolis, MN. Weschler, C. J., 2004. Chemical reactions among indoor pollutants: What we've learned in the new millennium. Indoor Air 14, 184‐194 Weschler, C. J., 2006. Ozone's impact on public health: Contributions from indoor exposures to ozone and products of ozone‐initiated chemistry. Environmental Health Perspectives 114(10), 1489‐1496 Weschler, C. J., Wisthaler, A., Cowlin, S., Tamás, G., Strøm‐Tejsen, P., Hodgson, A. T., Destaillats, H., Herrington, J., Zhang, J., Nazaroff, W. W., 2007. Ozone initiated chemistry in an occupied simulated aircraft cabin. Environmental Science & Technology 41, 6177‐6184 144
145
6 Appendices 6.1 Building material details 6.1.1 FC­1 Carpet ID Number: FC‐1 Manufacturer: Interface Flooring Lot Number: unknown Style/composition: 100% post‐consumer content type‐6 nylon loop pile of height 0.43 cm supported by recycled vinyl and fiberglass backing. The carpet had a total recycled content of 68%‐71%. Acquisition Date: 4/12/2009 Receiving Notes: The carpet was shipped in “tiles” of 50 cm × 50 cm × 0.7 cm to the University of Texas, Austin. Tile samples of FC‐1 were shipped by UT to S&T. Green Attribute: Recycled, California Higher Performance Schools, Low Emitting Materials 6.1.2 FC­2 Carpet ID Number: FC‐2 Manufacturer: Shaw Style: Casual Joy/Alaskan mist Lot Numbers: Dye Lot V44591, Mill order number 222216 Acquisition Date: 8/18/2009 Receiving Notes: Shaw Carpet was picked up from McCall’s Carpeting and transported directly to 207 Butler‐Carlton Hall. The carpet consisted of a 20 foot by 2 foot section of carpet wrapped in plastic sheeting. The carpet was stored as such until sample preparation and testing could be performed. Green Attribute: Recycled, California High Performance Schools Low Emitting Materials 6.1.3 FRf­1 Linoleum­style tile resilient flooring ID Number: FRf‐1 Manufacturer: Forbo Style: Marmoleum, Migrations, natural biege Lot Numbers: unknown Acquisition Date: 8/18/2009 Receiving Notes: Picked up from McCalls Floor‐mart, Rolla, MO. They consisted of 1’X1’ square tiles. As donated materials directly from the manufacturer, lot number and style were not specified. Green Attribute: Renewable, California High Performance Schools, Low Emitting Materials 6.1.4 FRf­2 Rubber puzzle­locking tile resilient flooring ID Number: FRf‐2 Manufacturer: Rubber Products/Rubber Cal Lot Numbers: none 146
Style: Green Puzzle‐lok recycled tire flooring Acquisition Date: 4/13/2009 Receiving Notes: The rubber tile was received as 2’X 2’X0.5” interlocking tiles, in room 210 Butler‐
Carlton and transported to room 207 Butler‐Carlton. They were left in the original shipping box to await sample preparation and testing. Green Attribute: Recycled rubber tires 6.1.5 FRf­3 Bio­based tiles, resilient flooring ID Number: FRf‐3 Manufacturer: Armstrong Floor Tile Lot Numbers: 99991 207638 Style: Green grass, migrations Acquisition Date: 8/18/2009 Receiving Notes: Armstrong biobased tile was picked up from McCall’s Carpeting in Rolla, Missouri and transported directly to room 207 Butler‐Carlton Hall. The 1’X1’tiles came in a standard shipping box of tile sheets. Green Attribute: Renewable, California High Performance Schools, Low Emitting Materials 6.1.6 FCf­1 Porcelain floor tile ID Number: FCF‐1 Manufacturer: American Olean Style: Red, unglazed porcelain Lot Numbers: SS033220 Acquisition Date: 4/24/2009 Receiving Notes: The 0.5’X0.5’ clay tiles were picked up directly from McCalls Flooring in Rolla, MO. The clay tiles were received in a cardboard box. Green Attribute: Likely low emitting 6.1.7 FWf­1 Renewable wood flooring ID Number: FWf‐1 Manufacturer: Green Floors Style: Mocha Hickory, finished Lot Number: HEDM001 Acquisition Date: 2/24/2010 Green Attribute: Renewable Receiving Notes: A 4’ box of Ecotimber wood flooring was received via UPS, which consisted of 12 pieces, 4” wide, 4’ long. The box was received in room 210 Butler‐Carlton Hall and moved to room 207 Butler‐Carlton Hall to await sample preparation and testing. Other product specifications: Dimensions * Thickness: 1/2" * Face Width: 5" * Lengths: Random (12"‐42") 147
Hardness * 1820 per Janka scale * 141% as hard as Red Oak Construction * Engineered 5‐ply, kiln‐dried, tongue & groove all four sides, beveled edges Finish * Satin sheen Aluminum‐oxide enhanced UV‐cured urethane finish * Scratch‐resistant hardened acrylic top‐coat 6.1.8 FWf­2 Renewable wood flooring ID Number: FWF‐2 Manufacturer: Smith & Fong Style: Plyboo, edge‐grain flooring, “Natural” pre‐finished FL‐V5872PA‐NAF Lot Number: 0654 Roll B223 Acquisition Date: 8/18/2009 Receiving Notes: Picked up from McCalls flooring. Received as 5/8"×35/8"×72" pieces in a cardboard box. Green Attribute: Renewable 6.1.9 WC­1 Cork wall tiles ID Number: WC‐1 Manufacturer: Unknown (purchased from EcoChoices Natural Living Store, Portuguese manufacturer name not provided) Style: Granito, pre‐glued Lot Number: Corkboard: ACP PL1505 Contact cement: Unknown Acquisition Date: 4/15/2009 Green Attribute: Renewable Receiving Notes: The corkboard was received as a box of 1’X2’ corkboard sheets, and a second box containing a paint roller and a one gallon bucket of the contact cement to use with the corkboard. The box, bucket and roller were all stored in room 207 Butler‐Carlton Hall after being retrieved from 210 Butler‐Carlton Hall, until sample preparation and testing could be performed. 6.1.10 WC­2 Acoustical Wall Panels ID Number: WC‐2 Manufacturer: Golterman & Sabo (made on contract for S&T) Style/composition: ecoCoustic Fiberglass core, Guilford 2100 finish, 402 green neutral, 100% polyester Lot Number: M‐38044 Acquisition Date: 2/2/2010 Receiving Notes: The wall paneling was received in a shipping box containing 6 pieces of circular 8.5” diameter, 1.5” thick panels to 210 Butler‐Carlton Hall, where they were then transported to 207 Butler‐
Carlton Hall until testing could be performed. Green Attribute: 35% post‐consumer recycled content 148
6.1.11 WC­3 Fabric wall covering ID Number: WC‐3 Manufacturer: Carnegie Fabrics Lot Numbers: Wall covering: THOM‐4798 Adhesive: 907805‐1 Style/composition: Xorel monofilament polyethylene fabric Acquisition Date: 4/23/2009 Receiving Notes: The Rayon Wall Covering was received via UPS in room 210 Butler‐Carlton Hall, as a roll of wall covering six feet wide and 20 feet long. The roll of wall covering was stored in room 207 Butler‐Carlton Hall to await sample preparation and testing. Green Attribute: Renewable 6.1.12 WP­1 Latex paint and primer ID Number: WP‐1a Manufacturer: Benjamin Moore Lot Numbers: Style/composition: 100% acrylic, flat finish (light blue). The paint contained a maximum of 25% titanium dioxide, 15% limestone, 5% silica and 5% diatomaceous earth. The primer contained water, acrylic resin, a maximum of 15% titanium dioxide and a maximum of 6% hydrous aluminum silicate. Acquisition Date: Receiving Notes: Green Attribute: low‐VOC 6.1.13 WP­2 Clay paint ID Numbers: WP‐2 Manufacturer: Bioshield Style/composition: Clay bright‐Burnt Orange 14. Water, clay, chalk, porcelain clay, cellulose, alcohol ester (binder), titanium dioxide pigment, Ecotints, preservative. Lot Numbers: unknown Acquisition Date: 1/10/2010 Receiving Notes: The clay paint was received in a one pint container, directly to 210 Butler‐Carlton Hall where it was moved to 207 Butler‐Carlton Hall. Green Attribute: Zero VOC 6.1.14 WP­3 Collagen paint ID Number: WP‐3 Manufacturer: EcoTrend Style/composition: Color 14‐0216 (light green), eggshell. Water, Titanium (di)oxide, natural amino‐
acrylic emulsion, talc, hydrolyzed collagen, calcium carbonate. Lot Number: Paint: 14‐0216 Primer: 260948 Acquisition Date: 4/22/2009 Green Attribute: Green Guard Certified Receiving Notes: EcoTrend Paint was received in a one gallon paint bucket via UPS in room 210 Butler‐
Carlton Hall and then transported to 207 Butler‐Carlton Hall to await sample preparation and testing. 149
6.1.15 WCP­1 Clay plaster ID Number: WCP‐1 Manufacturer: American Clay Style/composition: Loma Original Finish, Pigment: Santa Fe Tan Lot Numbers: Clay 57080‐00131; Primer 57080‐00144; Pigment 57080‐00115 Acquisition Date: 4/17/2009 Receiving Notes: American clay was picked up directly from Negwer Materials in Colombia, Missouri and transported directly to 207 Butler‐Carlton Hall on 4/17/2009. The primary clay substrate consisted of a 50 lb of dry clay powder with a label reading “Loma Original Finish.” The primer consisted of a 1 gallon bucket of primer labeled “Sanded Primer.” The pigment was a 1 pint container of dry pigment powder labeled “Plastic Color Pack” and was the “Santa Fe Tan” color. Green Attribute: Likely Low Emitting 6.1.16 WD­1 Recycled content drywall ID Number:WD‐1 Manufacturer: USG Style/composition: recycled content gypsum Lot Number: Acquisition Date: 4/12/2009 Green Attribute: Recycled Receiving Notes: Recycled drywall was purchased from a local distributor in Austin, Texas. The drywall sheets contained recycled paper backing covering reclaimed gypsum wallboard, and had dimensions of 121.9 cm × 243.8 cm × 0.635 cm. 6.1.17 CP­1 Ceiling tile ID Number: CP‐1 Manufacturer: Armstrong Style/composition: Baltic 1132, Home style ceilings, Fine fissured. Mineral fiber content. Lot Numbers: R3407 Acquisition Date: 2/7/2010 Receiving Notes: Armstrong ceiling tile was delivered, as a standard box of tiles, to Butler‐Carlton Hall and dropped off at the loading dock for Butler‐Carlton Hall. The box was then transported to room 207 to await testing. Green Attribute: California Higher Performance Schools, Low Emitting Materials, contains recycled post‐
consumer and post‐industrial products 6.1.18 CP­2 Ceiling tile ID Number: CP‐2 Manufacturer: Chicago Metallic Style: Eurostone, 50‐70% by weight expanded perlite, 15%‐30% by weight sodium silicate, and 5%‐15% by weight kaolin. Crystalline quartz may have been present as an impurity at less than 0.5% by weight. The ceiling tile density was 0.36 g cm‐3. Lot Number: 150
Acquisition Date: 3/23/2009 Green Attribute: Likely Low Emitting Receiving Notes: Picked up from Dallas, TX. Ceiling tiles were 60.9 cm × 60.9 cm × 2.22 cm. 6.1.19 CP­3 Ceiling tile ID Number: CP‐3 Manufacturer: Certainteed Style/composition: Cirrus 584HRC line, fiberglass composition Lot Number: E35421560 Acquisition Date: 2/11/2010 Green Attribute: California High Performance Schools, Low Emitting Materials Receiving Notes: Certainteed ceiling tile was delivered, as a standard box of tiles, to Butler‐Carlton Hall and dropped off at the loading dock for Butler‐Carlton Hall. The box was then transported to room 207 to await sample preparation and testing. 6.1.20 Latex drywall primer (*used as primer for WP‐2 and WP‐3 but not tested separately; primers not provided by these manufacturers) ID Number: none Manufacturer: Valspar Style/composition: White 260948 Lot Numbers: 9339055926 Acquisition Date: 4/30/09 Receiving Notes: Purchased directly from Lowes, Rolla, MO. Green Attribute: Low Odor 6.2 S&T method for analyzing dinitrophenylhydrazine derivatives of carbonyls High Pressure Liquid Chromatograph Method Software: Empower Software Autosampler: Waters 717plus Autosampler HPLC Controller: Waters 600 Controllers Detector: Waters 996 Photodiode Array Detector Column: Phenomenex P/No 006‐4435‐E0 Desc: Gemini 5u C18 110A Size: 250x4.60 mm 5 micron S/No: 294604‐18 Method Settings: 996 PAD: general: Starting Wavelength: 210.0 Ending Wavelength: 600.0 Sampling Rate: 0.50 151
Resolution 1.2 Auto Exposure: On Interpolate 656 nm Filter Response 1: On Analog Channel 1 Enable: On Analog Channel 2 Enable: Off Enable Events: Off Events: Default Channel 1: Output Mode Absorbance Bandwidth 4.8 Output Wavelength 360.0 Offset 0.000 Filter Type: Hamming Filter Response 0.0 Channel 2: Output Mode Off W600: general: Pump Type 600 E head volume 100 chart out % A Degas: A On B Off C On D Off Rate: 30 Channel: Enable Channel: Off Flow: High Limit: 5000 Low Limit: 0 Pump Mode: Gradient Time Flow %A %B %C 1 ‐ 1.00 40.0 0.0 60.0 2 20.0 1.00 30.0 0.0 70.0 3 21 1.00 0.0 0.0 100.0 4 26.0 1.00 0.0 0.0 100.0 5 27.0 1.00 40.0 0.0 60.0 6 32.0 1.0 40.0 0.0 60.0 Events: Don’t Change Solvents: A: H2O C: CAN Temperature: Temperature Set: 0.0 Temperature High Limit: 25.0 W717: general: Temperature Enable: Off Processing: Integration peak Width 15.0 Threshold@ 15.0 Min Area 0 Min Height = 0 Purity Start 190.0 Start 0.25 Stop 800 Stop 0.75 Purity Enable: Off Active Peak Region (%) 100.0 Threshold Criteria Auto Threshold Solvent Angle 1.00 Purity Possess 1 PAD Library Search None 10.0 None 3 Noise + Solvent 1.00 Component: None 5.00 Never CcalRef 1: Off 152
%D 0.0 0.0 0.0 0.0 0.0 0.0 Curve ‐ 6 6 6 6 6 6.3 S&T method for analyzing thermally desorbed carbonyls from Tenax tubes Thermal Desorber with Gas Chromatography/Flame Ionization Detector Method Software: Thermal Desorber: Unity Software GC/FID: 6890 GC Software Thermal Desorber: Ultra TD Markes International Limited GC/FID: Agilent Technologies 6890 N Network GC System (G 1530 N) S/#: US10332028 Method Settings: Thermal Desorber: Idle Split: True Purge Flow: 20 StandbyFlow: 20 ola Split Flow: 20 Purge Time: 1 Oven Temperature: 280 Minimum Carrier Pressure: 5 Desorb Time: 10 Purge Trap In Line: False Desorb Split: True Purge Split: True Desorb Flow: 80 Flow Pather Temeperature: 120 GC Cycle Time: 0 Oven: Initial Temp: 50 oC (on) Post Temp: 0oC Initial Time: 5.00 min Post Time: 0.00 min Ramps: Run Time: 31.67 min # Rate Final Temp Final Time Maximum Temp: 325oC 1 30.0 250 20.00 Equilibration time: 0.50 min 2 0.0 (Off) Inlet: Mode: Splitless Purge time: 999.99 min Initial Temp: 150oC (On) Total flow: 7.5 mL/min Pressure: 17.97 psi (On) Gas saver: Off Purge flow: 0.0 mL/min Gas type: Nitrogen Column: Capillary Column Mode: constant pressure Model Number: Agilent 19091J‐413 Pressure: 17.97 psi HP‐5 5% Phenyl Methyl Siloxane Nominal initial flow: 5.0 mL/min Max temperature: 325oC Average velocity: 67 cm/sec Nominal length: 30.0 m Inlet: Back Inlet Nominal Diameter: 320 um Outlet: Back Detector Nominal film thickness: 0.25 um Outlet Pressure: Ambient Detector: FID Temperature: 250oC (On) Makeup Gas Type: Nitrogen Hydrogen flow: 40.0 mL/min (On) Flame: On Air flow: 450 mL/min (On) Electrometer: On Mode: Constant Makeup flow Lit offset: 2.0 Makeup flow: 45.0 mL/min (On) Signal Data rate: 5 Hz Range: 0 Type: back detector Fast Peaks: Off 153
Save Data: On Zero: 0.0 (On) Column Comp Derive from back detector Post Time: 0.00 min Attenuation: 0 6.4 Test house, detailed results Table 6‐1. Light Aldehydes‐ Emissions Data ‐1
Emissions (μg hr )
‐1
Test Material Mixing Ozone vd (m h )
Low
Low
Low
Background
High
High
High
Low
Low
Low
w/ Ceiling Tile
High
High
High
SS1
SS3
Decay
SS1
SS3
Decay
SS1
SS3
Decay
SS1
SS3
Decay
2.12
3.43
1.48
1.46
1.73
2.28
2.12
1.41
0.99
1.84
2.42
3.17
C1
107.87
194.06
170.95
459.67
240.65
250.38
268.26
125.34
238.63
233.56
152.97
389.73
154
C2
0.00
109.00
47.48
390.62
0.00
19.03
0.00
243.40
0.00
3.49
98.75
76.52
AT
0.00
46.48
38.79
126.04
81.57
147.39
32.67
11.04
29.06
35.83
18.70
78.84
C3
0.00
5.38
5.19
23.14
0.00
8.16
0.00
46.24
7.47
0.00
32.45
0.00
C4
0.00
7.30
1.09
64.10
0.00
9.06
0.00
55.46
9.05
0.00
38.95
0.00 Table 6‐2. Light Aldehydes‐ Uncertainty Analysis ‐1
Test Material
Background
w/ Ceiling Tile
Mixing
Ozone
Low
Low
Low
High
High
High
Low
Low
Low
High
High
High
SS1
SS3
Decay
SS1
SS3
Decay
SS1
SS3
Decay
SS1
SS3
Decay
Emissions (μg hr )
C1
45.93
56.42
51.25
75.84
65.07
58.42
60.90
40.04
52.45
52.96
40.28
85.45
155
C2
80.98
86.68
93.23
94.05
113.77
95.71
32.91
49.98
62.77
62.18
36.51
63.77
AT
42.27
34.06
33.26
35.29
40.35
47.22
29.31
30.15
25.23
28.21
25.66
34.80
C3
13.45
7.89
6.76
8.00
10.00
9.54
13.68
14.51
18.42
14.22
13.23
17.34
C4
25.56
23.37
19.29
27.46
32.07
32.54
14.30
15.41
19.78
14.96
13.87
18.27
Table 6‐3. Heavy Aldehydes‐ Emission Data ‐1
‐1
Test Material Mixing Ozone vd (m h )
Low
Low
Low
Background
High
High
High
Low
Low
Low
w/ Ceiling Tile
High
High
High
SS1
SS3
Decay
SS1
SS3
Decay
SS1
SS3
Decay
SS1
SS3
Decay
2.12
3.43
1.48
1.46
1.73
2.28
2.12
1.41
0.99
1.84
2.42
3.17
C5
68.90
284.99
84.91
440.14
555.36
623.58
0.00
0.00
370.11
174.36
18.03
649.80
C6
543.18
1484.31
1690.16
2107.80
2237.43
3709.25
0.00
673.65
2257.97
1573.39
1446.78
4991.05
156
Emissions (μg hr )
C7
BA
C8
TA
82.02
0.00 218.92 0.00
230.14 0.00 233.95 0.00
222.37 0.00 245.75 0.00
374.23 0.00 542.65 0.00
381.63 68.36 498.92 0.00
486.00 265.86 541.58 53.31
0.00
0.00
0.00
0.00
51.02
0.00
92.87
0.00
262.59 64.11 329.43 0.00
269.93 18.65 359.47 0.00
172.65 0.00 200.38 0.00
564.17 0.00 773.71 0.00
C9
C10
289.27 36.43
154.00 162.21
256.54 17.76
423.94 76.75
329.60 38.52
494.71 56.61
0.00
0.00
67.36
0.00
251.96 0.00
285.08 38.93
108.35 5.24
494.56 25.34 Table 6‐4. Heavy Aldehydes‐ Uncertainty Analysis ‐1
Test Material
Background
w/ Ceiling Tile
Mixing
Ozone
Low
Low
Low
High
High
High
Low
Low
Low
High
High
High
SS1
SS3
Decay
SS1
SS3
Decay
SS1
SS3
Decay
SS1
SS3
Decay
C5
14.37
68.41
18.00
93.38
117.81
136.48
0.00
0.00
79.31
36.85
3.82
139.03
C6
125.30
340.59
302.48
405.94
400.90
676.27
47.48
134.72
427.59
264.66
245.68
858.59
C7
64.60
95.11
91.11
156.77
110.32
154.35
17.96
28.40
98.60
84.02
48.34
174.64
157
Emissions (μg hr )
BA
C8
112.64
72.50
95.43
96.84
88.24
68.65
127.71
144.63
85.94
106.40
64.82
122.43
61.27
11.97
58.13
25.48
56.94
86.31
55.98
74.90
31.39
41.72
142.74
171.65
TA
64.14
19.49
38.53
55.30
67.31
16.48
8.97
30.16
25.55
29.15
8.48
54.92
C9
114.85
124.84
81.43
127.89
112.43
109.69
26.12
45.80
94.93
65.25
24.07
136.03
C10
17.76
38.52
5.65
24.66
9.09
9.09
4.37
0.92
10.88
6.28
0.84
17.86