Volatile Organic Compounds in Indoor Air: Source Characterization

Volatile Organic Compounds in Indoor Air: Source Characterization

Volatile Organic Compounds in Indoor
Air: Source Characterization, Exposure
Modeling, and Control Strategies
Xudong Yang, Ph.D.
Cheung-Kung Professor
Dept. of Building Science, Tsinghua University
Outline
□ Introduction
□ IAQ control principle and criteria
□ IAQ control strategies
‹ Source control
‹ Ventilation
‹ Air purification
□ VOC regulations
□ Materials labeling
□ Design Tools
□ Summary and future perspective
We Work to Improve Indoor Environmental
Quality and Health
‡
‡
‡
Indoor air quality and air pollution control
Advanced air cleaning technologies
Sustainable building systems (energy efficiency and IAQ)
VOC Lab Facilities at Tsinghua Univ.
□ Small-scale environmental chamber system for material
VOC emission testing (Microchamber, FLEC, ASTM
53 liter, 1 m3 stainless steel)
□ Full-scale VOC test chamber system (30 m3 stainless
steel ,for large furniture, etc)
□ Full-scale air cleaning testing system (ASHRAE 52.2)
□ Bench-scale photocatalytic oxidation test systems
□ Chemical analysis equipment (PTRMS, Agilent GC/MS,
100-tube Markes thermal desorber, )
□ Indoor Air Quality (VOC) testing and certification
Indoor Environmental Engineering
□ Lighting
□ Acoustics
□ Thermal comfort
□ Indoor air quality (IAQ)
Energy efficiency and cost effectiveness
Indoor Air Quality (IAQ)
□ Concerns about IAQ are increasing
□ People spend most of their time indoors
□ The World Health Organization estimates up to
30% of office buildings have IAQ problems
□ Serious IAQ problems are rare, however
□ Causes of poor IAQ are not fully understood
Sick Building Syndrome (SBS)
□ Occupants complain of symptoms associated with acute
discomfort
‹ Headache; Eye, nose, or throat irritation
‹ Dry cough; Dry or itchy skin
‹ Dizziness and nausea
‹ Difficulty in concentrating; Fatigue
‹ Sensitivity to odors
□ The cause of the symptoms is not known
□ Most of the complainants report relief soon after leaving
the building
Common Causes of IAQ Problems
□ Ventilation
□ Outdoor contaminants
□ Indoor contaminants
□ Perceptions due to
‹ poor thermal conditions (e.g., high RH)
‹ poor lighting
‹ high noise level
‹ job stress, …, etc.
Indoor Air Pollution
WHO, U.S. EPA: One of the top environmental risks to public
health
‹
SBS，asthma or other diseases，lower productivity，shorter life
Economic loss
-U.S. $40-120 billion/year
-China >$13 billion/year
More severe problem in China
‹ New construction >1 billion m2/year
‹ Outdoor air pollution
‹ High emission materials used
Indoor Air Pollution
“Our building interiors, once thought of
as providing safe havens from the
pernicious effects of outdoor air
pollution and harsh climates, may
actually be more polluted than the
surrounding ambient environment”
Spengler and Chen, Annual Review of Energy
and Environment 2000
Five Trends in Building Construction &
Occupancy
A rise in the number of employees working in
office environment
An increase in the number of repetitive,
stressful, and ergonomically demanding jobs
Energy conservation measures resulting in
“tighter” buildings
Five Trends in Building Construction &
Occupancy (Cont’d)
An increase in the synthetic complexity of
building materials and furnishings
An increase in public sensitivity to health and
safety issues
Typical Air Contaminants
□ Inorganic gases
‹ CO, CO2, SO2, NOx, O3, etc….
□ Organic gases
‹ Volatile organic compounds (VOCs)
Ê
Formaldehyde, benzene, toluene, xylene, styrene, 1,4-dichlorobenzene,
4-phenyl cyclohexene (4-PC), nonane, decane, undecane, dodecane,
etc….
□ Radio active gases (e.g., Radon)
□ Particulate pollutants
‹ Bioaerosols derived from
Ê
Ê
Virus, bacteria, fungi, protozoa, dust mites, pollen
Asbestos, dusts, etc….
Typical Contaminant Sources: Outdoors
(From Prof. Jensen Zhang, Syracuse University)
Typical Contaminant Sources: Indoors
(From: TIME, Sept., 1998)
Typical Air Contaminant Sources
□ Outdoor air pollution
□ Building materials and furnishings
□ Office equipment (computers, copiers, printers,
…, etc)
□ Poorly maintained HVAC systems
□ Occupant activities
Building Material Emissions
(From Prof. Jensen Zhang)
Material Emissions (off-gassing)
□ More than 350 volatile organic compounds
(VOCs) identified
□ Indoor VOC concentrations are usually much
higher than outdoors
□ VOC emissions can be controlled through proper
selection of materials
Health Effects of VOCs
Short-term (acute) effects
‹ Odorous
‹ Irritation of eyes, nose, skin, and throat
‹ Headache, dizziness, fatigue
‹
Exacerbation of some diseases, e.g., asthma
Long-term (chromic) effects
‹ Respiratory and heart diseases
‹ Chronic illness (asthma, cancer, etc…)
2005 NRC (Canada) Target List of VOCs
□ Aldehydes
□ Ketones
□ Alcohols
□ Esters
□ Chlorinated Hydrocarbons
□ Aliphatic Hydrocarbons
□ Aromatic Hydrocarbons
□ Cyclic Hydrocarbons
□ Terpenes
□ Miscellanies
Total
9
5
12
6
11
17
18
7
8
2
95
IAQ Criteria for VOCs
□ Established exposure limits
‹ Threshold Limit Values (TLVs) by NIOSH & ACGIH
TLV-TWA: 8 hour/day, 40 hour/week, time weighted
average
Ê TLV-STEL: 15 minutes continuously, < 4 periods/day, >1
hour between periods
Ê TLV-C: instantaneous
Ê
‹
‹
Permissible exposure limit (PEL) by OSHA
Space Maximum Allowable Concentration (SMAC) by NASA
IAQ Criteria for VOCs
□ Guidelines for non-industrial environment
‹ Lowest of the established exposure limits
‹ 10% of TLV-C (ASHRAE Standard 62-1999)
‹ As low as possible for carcinogens
‹ Consult health expert
Ê
Ê
Where no standards exist
For environmentally hypersensitive people
TVOC Exposure - Effects (Molhave, 1991)
Concentration range
Effect
< 0.2 mg/m3
no irritation
0.2 - 3 mg/m3
the multifactorial exposure range
3 - 25 mg/m3
the odorous range
> 25 mg/m3
the toxic range (reduced wellbeing)
VOC from Building Measurements (USA)
EPA BASE study
Tel. Co. Admin. Buildings
1.2
1.2
1
1
TV O C (m g/m 3 )
T V O C (m g /m 3 )
(Shields and Fleischer, 1993)
0.8
0.6
0.4
0.2
0.8
0.6
0.4
0.2
0
0
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
Buildings
A
B
C
D
E
F
Buildings
G
H
I
J
Survey Result by China CDC (2002-2004)
VOC in urban residences decorated within one year, samples
randomly selected (from Prof. Dongqun Xu, China CDC)
VOC
Formaldehyde
Benzene
Toluene
Xylene
TVOC
Radon
Concentration
0.16±0.16 mg/m3 (n=1527)
0.124±0.273 mg/m3 (n=843)
0.259±0.673 mg/m3 (n=901)
0.189±0.561 mg/m3 (n=958)
2.18±12.94 mg/m3 (n=982)
43.8 Bq/m3 (n=3098)
60.11% residents had uncomfortable symptoms
40.8%
IAQ Criteria for VOCs
VOC
Conc.
Not
Indoor
VOC conc.
Standard E1
Outdoor VOC
Healthy
Healthy
Using unhealthy
materials, or
poorly ventilated
Indoor Air Quality (IAQ) Control
Goal：Ci<Ci,criteria
Source
Source
Control
Control
Ventilation
Ventilation
Health
HealthEffect
Effect
Air
Air
Purification
Purification
Source/emission Control
□ Source characterization
‹ Chemical analysis: What are emitted?
‹ Emission rates over time -- How fast, how long and
how much?
□ Minimization of source emissions
Emission Study: Small Chamber System
Sorbent Tube
Clean Air
Exhaust
Thermal
Desorber
Test Chamber
Test specimen
GC
MS/FID
Detector
The ASTM (53 liter) chamber
System Diagram (Small-scale Test Chamber)
(From Prof. Jensen Zhang)
Sampling
Dehumidifier
Water impinger
Injection
#1
Bypass
Rotameter
Exhaust
#1
Catalytic
Oxidizer
PR
Air filter
PR
Compressor
Mass flow
meter
T, RH sensor
Computer
Air Conditioning space
...
...
...
#2
#3
#4
Pressure
Gauge
Sampling System
(From Prof. Jensen Zhang)
Spring
SS gauze
Constant flow
sampling pump
Glass wool
CarboPack C
Groove
CarboPack B
Air flow
Chemical Analysis System (GC/FID and GC/MS)
Particleboard (at t=24 h, by GC)
9
1
1
1
1
2
2
2
2
3
3
3
3
4
4
4
1
1
2
3
4
5
6
7
2
3
6
5
4
Hexanal
α-Pinene
Cam phene
β-Pinene
α-Terpinene
Lim onene
γ-Terpinene
7
0
8
F
i
l
1
e
n
a
m
e
:
1
D
:
\
R
E
1
S
E
A
R
C
1
H
\
M
E
\
D
1
R
Y
_
P
R
O
2
D
\
W
O
O
2
D
\
P
A
R
2
T
B
O
~
1
\
2
P
B
0
4
\
P
2
B
0
4
-
0
4
.
3
R
U
N
3
3
C
h
a
n
n
e
3
l
:
A
=
3
F
I
D
4
4
4
4
Three Oil-based Wood Stains - Headspace
T
IC
: [B
S
B
1
]W
S
1
H
S
1
.D
A
b
u
n
d
a
n
ce
1
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e
+
0
7
1
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e
+
0
7
1
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e
+
0
7
1
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e
+
0
7
decane
WS3
1
.1
e
+
0
7
1
5
nonane
5
2-butanone
1
e
+
0
7
9
0
0
0
0
0
0
1
1
1
1
6
8
0
0
0
0
0
0
undecane
9
8 1
0
7
7
0
0
0
0
0
0
2
0
6
0
0
0
0
0
0
3
1
8
1
3
5
0
0
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1
7
1
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1
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4
0
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2
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0
0
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1
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0
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T
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e
>
2
6
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0
2
8
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0
3
0
.0
0
T
IC
:
3
2
.0
0
3
4
.0
0
3
6
.0
0
3
8
.0
0
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1
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5
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b
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5
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1
3
1
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e
+
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8
1
e
+
0
7
6
1
1
1
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6
9
0
0
0
0
0
0
1
5
4
3
1
8
0
0
0
0
0
0
1
9
1
8
7
0
0
0
0
0
0
2
6
0
0
0
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2
0
1
4
1
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7
5
0
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3
0
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>
2
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:
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Building Materials Tested
□ “Wet” materials
‹ wood stain, polyurethane, floor wax, paint
‹ adhesive, caulking
□ Dry materials
‹ particleboard, OSB, plywood
‹ oak, maple, spruce, pine
‹ gypsum wallboard, ceiling tile, vinyl tile
‹ carpet, underpad
□ Materials assemblies/furniture
General Approach
Source
Testing
Small-scale
chambers
Source
Modeling
IAQ
Design
Full-scale
rooms
Central task of source models: how to scale-up emission data?
Classification of Emission Models
Empirical Models
Physical Models
* Simple representation of emission * Based on mass-transfer
data (curve fitting)
* A “lump-sum” model
* Non-robust
* Simple
principles
* Distinguished mechanisms
* Robust
* Complex
Source Emission Study: “Wet” Source
(Wood Stain on Oak Board)
Emission Characteristics (“Wet” Source)
□ High initial emission rates and fast decay rate
□ Three emission periods
‹ evaporative controlled initial period
‹ transition period
‹ diffusion controlled final period
□ Affected by air velocity
Wood Stain: Small Chamber Tests (NRC
Canada Chamber)
Wood stain +
oak substrate
Electronic
balance
NRC Canada Chamber
Wood Stain: Emission Mechanisms
(Yang 1999; Yang et al., 2001)
Evaporation
Evaporation
Diffusion
Diffusion
Pore
Diffusion
Non-homogeneous
Diffusion
Homogeneous
A Four-layer Mass Transfer Model (Yang
1999; Yang et al., 2001)
V
C
Air
4
Interface
3
1
2
Material film
Substrate
Comparison Between Modeled and
Measured Emission Rates
(TVOC from wood stain on oak substrate)
a. First 2 hours
b. First 24 hours
10
3.0
Experiment
Experiment
1
VB model
VB model
2.0
CFD
0.1
CFD
0.01
1.0
0.001
0.0
0.0001
0.0
0.5
1.0
Elapsed time t (h)
1.5
2.0
0.0
6.0
12.0
18.0
Elapsed time t (h)
24.0
Emission Characteristics (Dry Materials)
□ Low emission rates and slow decay rate
□ Diffusion controlled process
□ Not affected by air velocity
□ Temperature and humidity may play an
important role
VOC Emission Study: Dry Source (Carpet)
A Diffusion Model For Dry Materials (Yang et al. 1998)
ˆ
Inside the material
∂ ⎛ ∂C ⎞
∂C
=
⎜D
⎟
∂x ⎝ ∂x ⎠
∂t
ˆ
x
o
At the material-air interface
C ( x = 0) = k eC a
ˆ At the air phase: convective mass transfer
C = concentration in the material;
t
= time;
D
= effective diffusion coefficient of a VOC in the material;
x
= the spatial coordinate (assuming 1-D diffusion).
Ca = concentration in air at the material-air interface;
ke = partition coefficient.
Air
Ca
C
Dry Source (SBR Carpet): Modeled vs. Data
(Yang et al. 1998)
TVOC concentration (1e-6 g/m3)
3500
3000
2500
data (23 C)
data (30 C)
data (40 C)
predicted (23 C, D=1.1e-14, Co=1.92e8)
predicted (30 C, D=4.2e-14, Co=1.60e8)
predicted (40 C, D=7e-14, Co=2.62e8)
2000
1500
1000
500
0
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22
Time (day)
Dry Source: Predicted Long-term Emission
TVOC concentration (1e-6 g/m3)
10000
t=23 C
t=30 C
t=40 C
1000
100
10
1
0
12
24
36
Time (month)
48
60
72
Comparison of Emissions: ”Green” vs “Nongreen”
Green
trex decking wood
Non-green
pres treated deck wood
ceramic floor tile
water-based paint
vinyl flooring
oil-based paint
wood stain
Emission Data: Pre-screening Analysis
(James and Yang 2004)
Material
Pressure-Treated Wood
Trex
Vinyl Floor Covering
Ceramic Floor covering
Water-Based Paint
Oil-Based Paint
Wood-Stain
Major VOCs
Toluene (5)
D-Limonene (2)
3-Carene (2)
3-Carene (2)
Camphene (4)
D-Limonene
Toluene
P-Xylene (4)
NONE
n-butyl-ether (0)
O-Xylene (4)
P-Xylene
2Butyl-1-Octanol (1)
TVOC Found (Toluene)
Emission Data: Pressure-treated Wood
0.01
0.009
3-Carene
D-Limonene
Toluene
TVOC
Conc. (mg/m3)
0.008
0.007
0.006
0.005
0.004
0.003
0.002
0.001
0
20
40
60
80
Elapsed Time (hr)
100
120
140
Emission Data: Trex Wood
Camphene
3-Carene
0.004
TVOC
Conc. (mg/mg3)
0.0035
0.003
0.0025
0.002
0.0015
0.001
0.0005
0
20
30
40
50
60
Time(h)
70
80
90
100
Emission Data: Pressure Treated vs. Trex
PTWood TVOC
Trex TvOC
0.012
Conc.(mg/m3)
0.01
0.008
0.006
0.004
0.002
0
20
40
60
80
Time(h)
100
120
140
Emission Data: ”Wet” Materials
TVOC WB Paint
400
TVOC WB Paint
Concentration (mg/m3)
350
TVOC Wood Stain
300
250
200
150
100
50
0
0
20
40
60
Time (h)
80
100
Small-scale Chambers vs. Full-scale Rooms
Small Chamber
Full-scale Room
* Small-piece sample
* Short-term
* Simple environmental conditions
(flow, T, RH, C, etc.)
* Large-piece material
* Long-term
* Complex env. cond.
A Full-scale Thermal & Air Quality Research Facility
at Syracuse University
Climate
Chamber
(6x12x10 ft)
Test
“wall”
Indoor
Environmental chamber
(16 ft x12 ft x10 ft high )
Climate
chamber
Separation or
test wall
Control
station
IEQ
chamber
HVAC System for IEQ Chamber
Testing section
for air cleaners
Emission rate of an office workstation (from Prof. Jensen
Zhang, Syracuse University)
e: R(t), mg/hr
20
Ventilation starts at t=
15
Test 1
10
Full Scale Chamber Measurements
~3 ACR
Rh=50%
3.05m
Isothermal
Decane
One-through mode
3.66m
Substrate:
Gypsum board
4.88m
latex paint premium primer
(Benjamin Moore & Co )
Emission test
Ceiling diffuser
Observation
window
Substrate is gypsum board
Paint
Outer layer
Gypsum Layer
Full Scale Chamber Measurements
1.0
Decane
t=0.5 hour
t=7 hour
t=20.4 hour
0.8
Z
0.6
point 6
0.4
0.2
decane
0.0
-2 0
2
4
6
8 10 12 14
Exposure (C/Ce)
Minimization of Source Emissions
□ Material selection
□ Pre-conditioning
□ Reformulation
‹ Oil versus water-based paints
□ Change of manufacturing processes
Strategies for IAQ Control
□ Source/emission control
□ Ventilation
□ Air purification
What is Building Ventilation?
□ Supply fresh/clean air
□ Remove contaminants
□ Maintain thermal comfort conditions
Adequate Ventilation for IAQ
□ Quality of outdoor air supply
□ Quantity of outdoor air supply
□ Good air distribution
‹ Deliver fresh air to occupants
‹ Remove/dilute contaminants
‹ Types of ventilation systems
Ê
Ê
Ê
Mixing ventilation
Displacement ventilation
Personal/local ventilation
Quantity of Outdoor Air (ASHRAE 62)
□ Prescriptive procedure
Max. Occupancy CFM (L/s)
Application (P/1000 ft2 or 100 m2)
per person
Office space
7
20 (10)
Classroom
50
15 (7.5)
Residential living area:
15 (7.5)
(& not less than 0.35 air changes per hour)
□ IAQ procedure (performance based)
Mixing Ventilation
(From Prof. Jensen Zhang)
Diffuser air jet
Return outlet
Cin
Flow entrainment & mixing
C
Ventilation Efficiency=(Cout-Cin)/(C-Cin)≈ Cout/C≈ 1.0
Cout
Displacement Ventilation
(From Prof. Jensen Zhang)
Return outlet
Upper zone
Stratification level
Lower zone with
minimal mixing
Thermal plume
C
Cin
Low velocity diffuser
Ventilation Efficiency=(Cout-Cin)/(C-Cin)≈ Cout/C > 1.0
Cout
Personal/local Ventilation
(From Prof. Jensen Zhang)
Return outlet
Partition
C
C
Personal air jets
Cin
Primary air
Under-floor supply air plenum
Ventilation Efficiency=(Cout-Cin)/(C-Cin)≈ Cout/C > 1.0
Cout
Estimating Human Exposure
□ Exposure estimation is essential to risk
assessment
□ There are two ways to estimate human exposure
to environmental pollution:
field measurement or modeling
Pros and Cons
□ Field measurements: reliable, but costly and
cannot predict
□ Modeling: can predict, but less accurate
A Computer Tool for IAQ Analysis
Ê
“MEDB-IAQ”- Material Emission Database and
IAQ Analysis (Developed by NRC Canada)
‹ A database
‹ A room simulation model
Impact of Material Selections and Ventilation on
Indoor Air Quality
MEDB-IAQ: selecting materials
MEDB-IAQ: selecting ventilation rate/schedule
MEDB-IAQ: predicting the concentrations
ACCESS-IAQ: A Code for Characterizing
Emission Sources, Sinks, and Indoor Air Quality
Source Model
Sink Model
Friction
B.C.
Airflow Model
Airflow data
ACCESS-IAQ
Thermal
B.C.
Exposure Model
Velocity
Temperature
VOC Conc.
Exposure
Risk Model
Yang 1999; Yang and Chen 2001
slot
Impact of Ventilation on Indoor
Pollutant Removal
exhaust
grille
exhaust
displacement
square
Human simulator
Displacement
Source
(SF6)
4
1
5
6
7
3
disp.
slot
grille
square
1
East
1
5A
4b
5b
2A
2b
slot
3B
5B
3A
1B
2B
South
North
0.8
0.6
Z 0.4
Z 0.4
0.2
0.2
1A
3A
0
0
0.4
square
2a
0.8
4a
West
5a
Grille
Disp.
1.2
1.6
0.8
1.2
1.6
C
1
1
0.8
0.8
0.6
0.6
Z 0.4
Experimental results
0.4
C
1A
door
0.8
0.6
1
3
1
Z
0.2
0.4
0.2
5A
0
2A
0
0.4
0.8
1.2
C
1.6
0.4
0.8
1.2
C
1.6
1
1
CFD model
validation
0.8
disp.
0.6
0.8
grille
0.6
Z 0.4
Z 0.4
0.2
0.2
1A
East
1
1A
5b
0
0
0.5
1
1.5
0
0
0.5
2b
4b
1
1.5
C
C
slot
1
1
slot
0.8
0.8
South
North
0.6
square
1
3
Z 0.4
0.6
Z 0.4
square
2a
4a
1A
0.2
0.2
door
1A
West
5a
1A
0
0
0.5
1
1.5
C
2
Grille
0.5
1
1.5
C
Disp.
2
1.00
1.
1.0
05
5
0.90
z
0.95
diffuser
00
Displacement
1.
1.00
0.90
0.5
0
0.60
0.85
0.80
0.75
0.70
x
0.55
0.55
0.50
Grille
z
0.60
0.80
0.
1.00
0
.7 0
90
1.10
x
0.6
5
diffuser
1.1
0
1.00
0.95
1.00
1.05
z
1.05
Square
1.15
1.05
1.00
1.10
1 .0 0
diffuser
1.20
1.25
1.30
0.95
x
0.80
0. 9
1
1.1 .0 0
0
1.40
0
1.10
1.40
1.5
0 0
.85
1.2 0
1.30
z
Slot
1.05
1.20
diffuser
0
1.3
0.95
1.0
1.40
1.50
1.60
0
x
1 .2 0
1.0
0.9
1.0
2
2
0.9
1.2
1.5
1.5 1.4 1.3
z
z
1.0
1
1.0
1.2
1.1
1.3
3
4
0.5
0
0
5
0.8
0.7 0.6
0. 5
0.9
0.9
1.1
1.2
0.0
2 1.2
0. 5
0
0
1.4 1.3 1.3 1.2
1.1
0.9 1.0
1
2
x
1.1
1.0
1
0.0
0.5
1.0
1.2
1.1
1.1
1
2
x
3
4
5
1.1
1.0
2
0.9
1.5
z
1.5
z
1
0.5
0. 5
2
x
3
4
5
0
0
1.1
0.5 0.0
0.6
1
0.8
1. 0
0.7
0.9
0.5
0
0
1
0.8
0.6
1
0.7
2
x
3
4
5
grille
0.55
0.55
0.50
Occupied zone
z
0.60
0.7
0.80
0.
1.00
0
0 .6
5
90
1.10
x
1.5
0.6 0.7 8
0. .9
0
1.0
1.1
1.2
1.2
1.5
z
z
1. 1
1
1.0
1.
2
1 . 11 . 2 1.3
1. 5
0.5
x
3
4
5
00
1.
1
0
0.8 .7
1.0 0
.9
1 .2 1
.1
4 1.3
6
2
0 .7
0 .6
1.
1
0.8
5
0.
2.0
0
0
0.3
0.4
1
0.5
0.2
2
1. 4
0 .5
2
2
x
3
4
5
“Ideal” Ventilation Mode
Occup.
Supply
Source
Exhaust
Strategies for IAQ Control
□ Source/emission control
□ Ventilation
□ Air purification
Air Purification Methods
□ Sorption by filter media
□ Oxidation or decomposition
‹ Photocatalytic oxidation
‹ Thermal decomposition/catalytic oxidation
‹ Ozone oxidation
‹ Air ionization (plasma decomposition)
‹ Botanical (plant) air cleaning
Sorption by Filter Media
□ Principles
‹ Physisorption
“van der Waals” or dispersion forces
Ê Reversible
Ê
‹ Chemisorption
Stronger chemical forces (covalent, ionic, or strong polar
bounding)
Ê Not reversible
Ê
Sorption by Filter Media
□ Typical media
‹ Granular activated carbon (GAC)
‹ Impregnated carbon
‹ Alumina/potassium permanganate (KMnO4)
‹ Zeolite (molecular sieve)
‹ Zeolite/KMnO4
‹ Physical blends of the above
Sorption by GAC Filter: a Typical Setup
(From Prof. Jensen Zhang)
Removal Efficiency = (Cin-Cout)/Cin x 100%
Sorption by GAC Filter: Removal Efficiency
(From Prof. Jensen Zhang)
Removal Efficiency (%)
120
toluene
formaldehyde
hydrogen sulfide
50% efficiency point
30% efficiency point
100
80
60
40
20
0
0
5000
10000
15000
20000
25000
30000
Exposure time (hr)
Unoccupied surface
Partially occupied surface
(Exposure time = 0 hr) (50% efficiency point )
Fully occupied surface
Sorbent Bed (from Jingjing Pei, Syracuse Uni.)
Simulate the performance of sorbent-bed based
gas phase air cleaners by describing VOC
transportation in porous media
Courtesy Jinjing Pei, Syracuse Univ.,
USA
96
Physical Analysis: Description of Basic Phenomena
(from Prof. F. Allard, Univ. La Rochelle)
Cs
De
C
Internal Pore
Coating
External
Flow
Boundary layer
Porous Material
Ds
Courtesy Prof. F Allard, Univ. La
Rochelle, France
Photocatalytic Oxidation
Conduction band
eReduction
UV(300-370nm)
hv
recomb.
VOCs Æ CO2, H2O, etc
Oxidation
Valence band
h+
Photo-Catalytic Oxidization
(Based on Prof. Y. Goswami, Univ of Florida)
PPT after Prof. Y. Goswami, Univ of Florida
Pollutant Cleanup
PCO Effectiveness Test: Set-up
Catalyst-coated
Glass-plate
Flow meter
Inlet
Sample
port
Compressed
Air
VOC Source
UV/fluorescent
Lamp
Stainless steel
GC-ATD
Quartz
Window
Outlet
Sample
port
Reactive Surface: Destruction of formaldehyde
under visible (15W fluorescent) light: 2.8 cm I.D. x 26
cm tubular reactor
Formaldehyde - Formaldehyde injection only
(Time 0 = Time point of turning on the light)
Reactor Inlet
Reactor Outlet
Concentration (ppm)
4
3
2
Light On
Light Off
1
0
-1
0
1
2
Time (hr)
Yang et al. US Patent in process
3
4
On-site Reactive Coating
Reduces VOC emissions from materials
Paint Reference
Paint with gel/light
VOC
H2O
CO2
Concentration (mg/m 3)
8000
7000
6000
5000
4000
3000
2000
1000
0
0
20
40
60
Time (h)
Yang et al. US Patent in process
80
100
120
On-site Reactive Coating
For emission reduction from woods and surface coatings
Strategies for IAQ Control
□ Source/emission control
□ Ventilation
□ Air purification
Integration for optimization
‹ IAQ
‹ Energy efficiency
‹ Cost effectiveness
Thank you !