ESD and Safety Guidelines

ESD and Safety Guidelines
Contents
Contents
1 About the ESD and Safety Guidelines....................................................................................................................3
2 General Safety Measures.......................................................................................................................................5
2.1 Material Safety Data Sheets (MSDS)........................................................................................................5
2.2 Hazard Statements....................................................................................................................................6
2.3 Workplace Environmental Hazards...........................................................................................................7
3 Safety Guidelines for Handling Chemicals.............................................................................................................9
4 Electrostatic Discharge (ESD) Guidelines............................................................................................................10
4.1 ESD Equipment.......................................................................................................................................11
4.1.1 Cleaning ESD-protective Clothing..............................................................................................12
5 Lockout/Tagout Safety Guidelines and Procedures..............................................................................................13
6 Refrigeration and Coolant Guidelines...................................................................................................................16
7 Laser Safety..........................................................................................................................................................17
2
About the ESD and Safety Guidelines
1
About the ESD and Safety Guidelines
The ESD and Safety Guidelines provides information to prevent personal injury and equipment damage during
maintenance and repair of Cray® systems.
Release Information
Table 1. Record of Revision
Publication Title
Publication Number
ESD and Safety Guidelines
Date
March 2016
ESD and Safety Guidelines
HGM-016-H
February 2011
ESD and Safety Guidelines
HGM-016-F
December 2010
ESD and Safety Guidelines
HGM-016-E
November 2007
ESD and Safety Guidelines
HGM-016-D
June 2002
ESD and Safety Guidelines
HGM-016-C
December 2001
Typographic Conventions
Monospace
Indicates program code, reserved words, library functions, command-line prompts,
screen output, file/path names, key strokes (e.g., Enter and Alt-Ctrl-F), and
other software constructs.
Monospaced Bold
Indicates commands that must be entered on a command line or in response to an
interactive prompt.
Oblique or Italics
Indicates user-supplied values in commands or syntax definitions.
Proportional Bold
Indicates a graphical user interface window or element.
\ (backslash)
At the end of a command line, indicates the Linux® shell line continuation character
(lines joined by a backslash are parsed as a single line). Do not type anything after
the backslash or the continuation feature will not work correctly.
Scope and Audience
This publication is written for Cray employees, Cray contractors, and Cray customers.
3
About the ESD and Safety Guidelines
Feedback
Visit the Cray Publications Portal at http://pubs.cray.com and make comments online using the Contact Us button
in the upper-right corner or Email [email protected]. Your comments are important to us and we will respond within
24 hours.
Trademarks
The following are trademarks of Cray Inc. and are registered in the United States and other countries: CRAY and
design, SONEXION, URIKA, and YARCDATA. The following are trademarks of Cray Inc.: APPRENTICE2,
CHAPEL, CLUSTER CONNECT, CRAYDOC, CRAYPAT, CRAYPORT, DATAWARP, ECOPHLEX, LIBSCI,
NODEKARE. The following system family marks, and associated model number marks, are trademarks of Cray
Inc.: CS, CX, XC, XE, XK, XMT, and XT. The registered trademark LINUX is used pursuant to a sublicense from
LMI, the exclusive licensee of Linus Torvalds, owner of the mark on a worldwide basis. Other trademarks used in
this document are the property of their respective owners.
4
General Safety Measures
2
General Safety Measures
Observe the following safety measures while installing, repairing, or maintaining any Cray Inc. system.
●
Do not wear watches or jewelry while working on system components.
●
If a procedure requires two people to complete, do not perform the procedure alone.
●
Review proper lifting techniques when lifting heavy objects.
●
Keep fingers and conductive tools away from high-voltage and high-current areas.
●
Set circuit breakers to the OFF or OPEN position, when a procedure requires it, before starting any removal,
installation, or repair process.
●
Remove all tools from the equipment after completing the replacement or repair.
●
Replace all covers and panels removed from the equipment.
●
Power off the system only after shutting down the system software in an orderly manner.
2.1
Material Safety Data Sheets (MSDS)
The material safety data sheet (MSDS) is the primary source of detailed information on the health and safety
precautions for use of a chemical. Obtain MSDSs for products that are used on or within Cray machines by
contacting Cray’s MSDS on-demand vendor, 3E, at 1-800-451-8346. The number is staffed 24 hours a day, 7
days a week.
Figure 1. MSDS 3E
Provide local medical facilities and poison control center with a copy of the MSDS for hazardous chemicals.
Request that these facilities keep the MSDS on file. Inform them that the medical hot line number for 3M is
1-651-733-2882. In addition, if an individual is exposed to decomposition vapors, be sure that an MSDS
accompanies him/her to the medical facility or poison control center.
NOTE: MSDSs are subject to change. Contact the Cray Safety Department, the manufacturer, or Cray’s
MSDS vendor (3E Company) for the latest version of the MSDS for hazardous chemicals.
5
General Safety Measures
2.2
Hazard Statements
Hazard statements appear in repair and maintenance documentation to alert the reader of potential danger they
might encounter while servicing Cray equipment. Examples of the hazard statements for Danger, Warning, and
Caution are shown below.
Danger
Danger statements indicate an imminently hazardous situation that, if not avoided, will result in death or serious
injury.
Figure 2. Example of Danger Statement
DANGER:
●
Electrical Hazard
●
Do not touch. Contact with this component will result in a fatal electrical shock.
Warning
Warning statements indicate a potentially hazardous situation that, if not avoided, could result in death or serious
injury.
Figure 3. Example of Warning Statement
WARNING:
●
Burn Hazard
●
Be careful while servicing the RCU enclosure; several hot surfaces exist within the enclosure. Contact
with the hot surfaces could result in severe burns.
Caution
Caution statements indicate a potential situation which, if not avoided, may result in property damage or in
an undesirable result or state.
6
General Safety Measures
Figure 4. Example of Caution Statement
CAUTION:
2.3
●
ESD Hazard
●
Observe all ESD precautions. Failure to do so can result in damage to the equipment.
Workplace Environmental Hazards
Several conditions exist within refrigeration and power distribution systems that can be hazardous and even lethal
if not handled with caution. Observe the following safety precautions when working on or near refrigeration
systems, power distribution systems, or other computer system components.
High Temperatures
Be careful when working on or near computer system equipment that generates high temperatures. Surface
temperatures of some equipment can exceed 200°F (93°C).
Tripping Hazard
Keep work areas clear of obstacles that could cause someone to trip and fall.
Eye Protection
Wear splash-proof monogoggles, or both safety glasses with side shields and a wraparound full-face shield to
protect your eyes against hazards of solid objects or liquids that may come in contact with your eyes.
High Noise Levels
Wear hearing protection if you are subjected to excessive noise levels (over 110 dBs) for more than 15 minutes at
a time. Generally, if people have to raise their voices to be heard, they are working in an area that requires
hearing protection.
Dielectric Coolant
Dielectric coolant removes heat from electrical components in the computer system. Handle it with appropriate
care after reading the manufacturer’s MSDS.
Explosion Hazard
Be careful when working with pressurized containers. Pressurized containers present explosion hazards if
dropped or exposed to open flame.
7
General Safety Measures
Moving Parts
Be careful when working near machinery that contains moving parts that may cause injury. Be especially alert for
rotating fans in cooling units that may start up at any time and without warning.
Strain or Crush Hazard
Secure rolling equipment tightly. Unrestrained equipment (such as a power-supply assembly) could roll out and
cause serious injury to personnel.
Proper Lifting Techniques
Review proper lifting techniques when lifting heavy objects. Before lifting, take a moment to think about what you
are about to do. Examine the object for sharp corners, slippery spots or other potential hazards. Know your limit
and do not try to exceed it. Ask for help if needed.
8
Safety Guidelines for Handling Chemicals
3
Safety Guidelines for Handling Chemicals
Observe the following safety measures while handling any chemical:
●
Identify the chemical(s) before use.
●
Never sniff a chemical to identify its type or location.
●
Know the location of eyewash stations and safety showers and how to use them.
●
Never put hands into corrosives or solvents, even if wearing gloves.
●
Read the chemical hazards on the Material Safety Data Sheets (MSDSs) before using chemicals.
●
Use appropriate personal protective equipment (PPE). Eye protection equipment can include splash-proof
monogoggles, or both safety glasses with side shields and a wraparound full-face shield. Other PPE includes
protective gloves, barrier creams, splash aprons, and corrosive resistant boots or any combination of these
items.
●
Make sure that all PPE fits properly and is used properly.
●
Do not wear contact lenses. Contact lenses can absorb chemicals or trap them against the eye.
●
Always wash hands thoroughly before and after handling any chemical, and especially before eating or
smoking.
●
Follow proper workplace procedures.
●
Use and maintain required safety equipment properly.
●
Do not eat, drink, or smoke in chemical-use areas.
●
Use and maintain adequate personal decontamination equipment.
●
Keep the workplace clean.
●
Develop an attitude of safety awareness.
9
Electrostatic Discharge (ESD) Guidelines
4
Electrostatic Discharge (ESD) Guidelines
About Electrostatic Discharge (ESD)
Electrostatic discharge is the rapid movement of an electrical charge from one object to another.
Walking across the carpet can generate several thousand volts of electrical charge on your body that will cause
severe damage when coming into contact with electronic components or entire circuit card assemblies. This
shock, or release of energy, is known as electrostatic discharge.
The amount of voltage that causes permanent damage in an electrostatic discharge incident is not high enough to
be felt, heard, or seen. Nevertheless, the damage will occur.
ESD damage takes time to appear as a hard failure. Always adhere strictly to ESD precautions to avoid damage
equipment.
When used properly, ESD control equipment prevents electrostatic damage to computer systems and electrical
components.
For more information regarding the control of ESD, contact Site Engineering at [email protected].
ESD Caution Statement
Look for caution statements like the one below to warn you that the equipment being serviced with is ESD
sensitive that requires appropriate precautions.
Figure 5. ESD Hazard Statement
CAUTION:
●
ESD Hazard
●
Observe all ESD precautions. Failure to do so can result in damage to the equipment.
ESD Guidelines
Follow these guidelines while handling ESD-sensitive equipment:
●
Assume all components and assemblies are ESD sensitive.
●
Handle ESD-sensitive material only when properly grounded and at an ESD-safe workstation.
●
Avoid direct contact between ESD-sensitive material and plastic and calculators.
●
Handle defective devices using the same precautions as with good material.
10
Electrostatic Discharge (ESD) Guidelines
●
Avoid activities such as rubbing, which cause ESD.
●
Keep materials such as plastic, Styrofoam, cellophane tape, nylon, wool, food, and beverages out of the work
area.
●
Keep unprotected personnel out of your work area.
●
Keep work area clean.
●
Remove all unnecessary materials from work area.
●
Handle devices and boards only by the edges.
●
Do not touch the components, conductors, or connector pins. Keep parts in their antistatic or static shielding
bags until ready for use. Remove the part from the antistatic or static shielding bag only when properly
grounded to the cabinet ground with proper grounding equipment.
NOTE: The outside of a static bag is not ESD safe, only the inside. Do not place components directly
onto an antistatic bag. Turn the bag inside out before placing the component on it.
●
Place removed equipment on an antistatic mat.
NOTE: Blue antistatic mats should be used wherever possible because they provide a slow drain of a
static charge buildup. Black mats are conductive and components placed on them are more likely to
receive a severe static discharge. However, black mats are acceptable when used in a completely
ESD-protected area.
●
Do not place an unprotected device/board on top of any unprotected component or on any surface that is not
dissipative or antistatic.
●
Use proper grounding equipment while connecting or disconnecting boards or peripherals.
●
Ensure that your body and all electrical equipment are at a ground potential to avoid damage from ESD.
4.1
ESD Equipment
ESD-safe Work Space
Whenever possible, prepare an ESD-safe work space to perform repairs. Use a blue ESD ground mat and static
monitor if they are available. ESD shoes in an ESD-safe work space are necessary for proper grounding.
ESD Smocks
Wear an approved static-dissipative smock to service or handle an ESD-sensitive device. Completely button up
the smock and wear it as the outermost layer of clothing. A portion of the smock sleeves must be in direct contact
with the skin. Tuck hair that exceeds shoulder length inside the back of the smock.
ESD Shoes
Wear approved static-dissipative shoes or approved dissipative heel straps on both shoes to service or handle an
ESD-sensitive device. When sensitive equipment is exposed to static discharge, ESD shoes help prevent an
excessive charge from building when your body is in contact with conductive flooring. ESD shoes should be used
with a properly grounded work space.
11
Electrostatic Discharge (ESD) Guidelines
Heel Straps
Apply heel straps to the heels of both shoes if not wearing ESD-safe shoes. Heel straps are required on both
shoes to protect computer equipment from ESD.
ESD Wrist Straps
ESD wrist straps provide a backup to provide grounding if the work space is not properly grounded. Skin contact
is essential for a dissipative path to earth ground through your wrist strap. If possible, connect the wrist strap cord
directly to earth ground to provide a discharge path. Otherwise, use a wrist strap plug to connect the wrist strap
cord to a special ground mat. This ensures that an effective path exists to earth ground. Periodically test your
wrist strap cord with an ohmmeter to ensure that an effective path to ground exists. A properly working wrist strap
should measure between 950 kilo-ohms and 10 megohms when it is checked with an ohmmeter.
Order ESD Equipment
Contact Cray Manufacturing in Chippewa Falls (715-726-4000) to purchase ESD equipment.
4.1.1
Cleaning ESD-protective Clothing
ESD clothing must be clean for proper operation. Soil buildup on static-dissipative clothing greatly decreases the
dissipative flow of static charges to ground.
ESD Wrist Straps
ash elastic wrist straps in warm soapy water, rinse them with hot water, and allow them to air-dry. ESD wrist
straps may also be inserted in the pockets of the ESD smock and washed with the smock. Periodically check the
wrist strap cord with an ohmmeter to ensure that it is not defective. A properly working wrist strap should measure
between 950kΩ and 10MΩ when measured with an ohmmeter.
ESD Smocks
Manufacturers recommend that ESD smocks be washed in warm water, rinsed with cool water, and dryed using
the permanent press cycle. Do not use chlorine bleach. Replace the smock after 50 to 75 washings or if the
smock is torn.
ESD Shoes
Clean the top bottom of the ESD shoes periodically with either soap and water or denatured alcohol.
12
Lockout/Tagout Safety Guidelines and Procedures
5
Lockout/Tagout Safety Guidelines and Procedures
Lockout/Tagout means to apply a lock and a tag to a piece of equipment or an electrical panel to ensure that the
equipment that you service cannot be operated until the lock and tag are removed.
All employees are required to follow lockout/tagout procedures when servicing Cray equipment. The lockout/
tagout procedures ensure that all potentially hazardous energy is locked out and isolated before anyone services
the equipment.
Lockout/tagout hazard statements are used throughout manuals to enforce all lockout/tagout procedures.
Isolating Electrical and Mechanical Energy Sources
Always isolate and lock electrical energy sources and mechanical energy sources such as hydraulics and
pneumatics, pressurized water, steam, and refrigerants before performing maintenance.
Normally, electrical and mechanical energy systems have devices such as disconnects and valves that enable
you to isolate the energy source. When pressurized lines are part of the energy system, reduce the pressure in
the system before servicing the equipment. If the system uses refrigerant, recover any refrigerant that escapes
from the system when bleeding the pressure.
Perform the following tasks (when they apply to the equipment being serviced) to isolate electrical and
mechanical energy sources.
●
Lock and tag all equipment that uses or produces electrical energy, including motors and generators.
●
Isolate the hydraulic lines from the components being serviced. After isolating the equipment energy source,
bleed pressure from the lines.
●
Isolate the pneumatic lines from the components being serviced. After you isolate the equipment energy
source, bleed pressure from the lines.
●
Isolate the valves on the equipment with pressurized water or steam line from the components being
serviced. After isolating the equipment energy source, bleed pressure from the lines.
●
Isolate the refrigeration lines from the components being serviced. After isolating the equipment energy
source, recover the refrigerant in the lines.
●
Isolate and lock all equipment that contains devices that can store mechanical energy, such as flywheels
and springs.
Lockout/Tagout Procedure
Use the following steps as guidelines to lock and tag equipment before servicing.
1. Survey the area to locate all energy sources and to determine which switches, valves, or other energyisolation devices apply to the equipment that you must lock and tag.
2. Notify all affected employees that a lockout is required and will soon take place. Be sure to state the reason
for the lockout.
13
Lockout/Tagout Safety Guidelines and Procedures
3. Verify correct operation of your voltage measurement equipment or multimeter by measuring the voltage of a
known power source. Ensure that the meter leads are fully insulated and are not damaged.
4. Shut off the equipment being serviced by its normal means (toggle switch, stop button, etc.)
NOTE: Use the left-hand rule when operating electrical switches in an electrical panel. Stand on the
unhinged side of the panel or disconnect, face away, and use your left hand to shut off the switch.
This positions your body out of the way in case an electrical short circuit occurs.
5. Operate all switches, valves, or levers to ensure that all stored energy is dissipated. Stored energy may be in
the form of capacitors, springs, elevated machine members, rotating flywheels, hydraulic systems, gas, steam
or water pressure, etc.
6. Lock and tag the energy-isolation device with an assigned individual lock and tag.
7. Use a multimeter to verify that no voltage is present on the electrical circuit that feeds the equipment being
serviced.
8. After verifying that no personnel are near the equipment, activate the equipment operating controls once
again to verify that the equipment will not operate. Be sure to return the controls to the off position after the
test.
The equipment is now locked and tagged. Maintenance or service activities can now begin.
Group Lockout/Tagout Procedure
If more than one person is required to lock and tag a piece of equipment, each person must place his/her own
lock and tag on the energy-isolation device(s). If the energy-isolation device(s) cannot accept multiple locks or
tags, use a multiple lockout hasp.
Restoring Equipment to Service
Use the following steps as guidelines for restoring equipment to service.
1. Remove all tools from the work area.
2. If you removed any machine guards, reinstall them.
3. Check the area to ensure that no personnel are near the equipment.
4. Remove all locks and tags from the energy-isolation device(s).
5. Test run the equipment and ensure that it operates normally.
Removing a Lock and Tag Installed by Another Employee
Another employee may remove a lock and tag only when the following conditions exist:
1. You verify that the employee who originally applied the lock and tag is not at the facility.
2. You have made a reasonable effort to contact the employee for permission to remove the lock and tag.
If these conditions do not exist, the lock and tag can be removed only with the approval of the immediate
supervisor of the absent employee. The employee must be notified before resuming work that his/her lock and tag
were removed.
If maintenance or service activities must continue after a shift or personnel change, the lock and tag must remain
until an employee on the next shift affixes his/her lock and tag.
Only authorized employees can remove locks and tags that employees attached during the previous shift.
14
Lockout/Tagout Safety Guidelines and Procedures
Lock and Tag Criteria
Locks must meet the following criteria:
●
Master Lock Number 3 or equivalent
●
Withstands exposure to wet and damp conditions
●
Standardized within the workgroup
●
Substantial enough to prevent accidental removal
Tags must meet the following criteria:
●
Able to withstand exposure to wet and damp conditions
●
Standardized in print and format
●
Identifies the individual by name
15
Refrigeration and Coolant Guidelines
6
Refrigeration and Coolant Guidelines
Refrigeration Certification
CFCs (chlorine, fluorine, and carbon) and HCFCs (hydrogen, chlorine, fluorine, and carbon) are ozone-depleting
substances and are used in the Liebert XDP coolant pumping units, or coolant distribution units (CDUs) that cool
some Cray computer systems. Federal regulations require certification before handling any ozone-depleting
refrigerant. If not personally certified for handling refrigerant, contact Field Technical Support before servicing
coolant pumping units, or CDUs.
Reclaiming Refrigerant
To comply with federal regulations that protect the environment’s stratospheric ozone layer, it is necessary to
reclaim all refrigerant when servicing cooling systems. Use approved recycling and reclamation equipment
whenever recovering refrigerant. Failure to use proper equipment and procedures may result in fines and/or
criminal prosecution.
Take the following safety precautions before servicing any refrigeration equipment or handling any refrigerant:
●
Always wear personal safety equipment such as safety glasses (with side shields) and gloves.
●
Never perform any service on a system without first consulting the appropriate document(s) for the
equipment.
●
Avoid breathing vapors or mist from accidental discharges.
●
Never transfer refrigerant to a tank or cylinder unless the container is approved for refilling by the Department
of Transportation (DOT).
●
Never fill a refrigerant container to more than 80 percent of its capacity. The remaining 20 percent is
necessary to allow for thermal expansion of the refrigerant.
16
Laser Safety
7
Laser Safety
The term LASER is an acronym that stands for Light Amplification by Stimulated Emission of Radiation. Thus the
laser is a device that produces and amplifies light. The laser produces a unique and desirable light that is almost
impossible to obtain by any other means.
Safety Guidelines
Always follow these safety guidelines:
●
Never look into fiber-optic wave guides.
●
Read and follow the information on all caution/warning/danger labels before you apply power to a system.
●
Always attach the connector to the fiber-optic cable before you apply power to the system. This ensures that
all light is confined within the fiber-optic wave guide, which practically eliminates any potential hazard.
●
Never look into the end of a fiber-optic cable to confirm that light is being emitted. Most fiber-optic laser
wavelengths (1300 nanometer [nm] and 1550 nm) are invisible to the eye and cause permanent damage.
Shorter wavelength lasers (for example 780 nm) are visible and can cause significant eye damage. Always
use an optical power meter to verify light output.
●
Never look into the end of a fiber-optic cable on a powered device with any type of magnifying device such as
a microscope, eye loupe, or magnifying glass. This causes a permanent, irreversible burn on the retina of the
eye.
Laser Beam Parameters
The following properties are common to all laser beams and are the factors which, in combination, distinguish
laser outputs from other sources of electromagnetic radiation:
●
A nearly single frequency operation of low bandwidth (that is, an almost pure monochromatic light beam).
●
A beam with a Gaussian beam intensity profile.
●
A beam of small divergence.
●
A beam of enormous intensity.
●
A beam that maintains a high degree of temporal and spatial coherence.
●
A beam that is, in many laser devices, highly plane polarized.
●
A beam with enormous electromagnetic field strengths.
Types of Lasers
Lasers are commonly designated by the type of lasing material employed. There are four types:
●
Solid-state lasers
●
Gas lasers
17
Laser Safety
●
Dye lasers
●
Semiconductor lasers
Modes of Operation
The different time modes of operation of a laser are distinguished by the rate at which the laser delivers energy.
There are five modes:
●
Continuous wave (CW)
●
Single pulsed (normal mode)
●
Single pulsed Q-switched
●
Repetitively pulsed
●
Mode locked
Classes of Laser
Lasers and laser systems comprise four broad Classes (I to IV).
Class I: cannot emit laser radiation at known hazard levels. Users of Class I laser products are generally exempt
from radiation hazard controls during operation and maintenance.
Class IIA: a special designation that is based upon a 1000-second exposure and applies only to lasers that are
not intended for viewing such as a supermarket laser scanner.
Class II: low-power visible lasers that emit above Class I levels but at a radiant power not above 1 mW. The
concept is that the human aversion reaction to bright light will protect a person.
Class IIIA: intermediate power lasers (cw: 1-5 mw). Class IIIA lasers are hazardous if you look directly at the laser
beam. Some limited controls are usually recommended.
NOTE: There are different labeling requirements for Class IIIA lasers. A caution label is required for
lasers with a beam irradiance that does not exceed 2.5 mw/cm (2). A danger label is required for lasers
with a beam irradiance that exceeds 2.5 mw/cm (2).
Class IIIB: moderate-power lasers. In general Class IIIB lasers are not a fire hazard, nor are they generally
capable of producing a hazardous diffuse reflection.
Class IV: high-power lasers that are hazardous to view under any condition (direct or diffuse) and are a potential
fire hazard and a skin hazard. Significant controls are required at Class IV laser facilities.
Optical Fiber Communication Systems (OFCSs)
Optical fiber communication systems and the associated optical test sets use semiconductor lasers or LED
transmitters that emit energy at wavelengths typically greater than 700 nanometers (nm) into the lightguide fiberoptic cables.
All OFCSs are designed to operate with the beam totally enclosed within the fiber optic and associated equipment
and therefore are always equivalent to Class I in normal operation. The only risk for exposure occurs during
installation and service when lightguide cables are disconnected or during an infrequent accidental cable break.
OFCSs are assigned to one of four service group (SG) designations: SG1, SG2, SG3a, or SG3b, depending on
the potential for an accessible beam to cause biological damage. The service group designations indicate the
potential for eye hazards to occur only when the beam is exposed. This normally occurs only during periods of
18
Laser Safety
service to an OFCS. Such designations apply only during periods of service in one of the following four service
groups (SGs):
●
SG 1: An OFCS that is SG1 has a total output power that is less than the accessible emission limit (AEL) for
Class I and there is no risk of exceeding the maximum permissible exposure (MPE) when a user views the
end of a fiber with a microscope, an eye loupe, or the unaided eye.
●
SG 2: An OFCS is SG2 only if it emits wavelengths between 400 and 700 nm and is potentially hazardous if
the user views it for more than 0.25 seconds.
NOTE: At present, virtually no OFCS operate in this wavelength range.
●
SG3A: An SG3A OFCS is not hazardous when viewed with the unaided eye and is hazardous only when
viewed with a microscope or an eye loupe.
●
SG 3B: OFCSs that exceed the previous criteria are designated as SG 3B.
NOTE: OFCSs in which the total power is at or above 0.5 W do not meet the criteria for optical-fiber
service group designation. In this case, the OFCSs are treated as a standard laser system.
Laser Hazards
Laser radiation of sufficient intensity and exposure time can cause irreversible damage to the skin and eye. The
most common cause of laser-induced tissue damage is thermal damage.
Eye Injury: A laser beam of sufficient power can theoretically produce retinal intensities that are orders of
magnitude greater than conventional light sources, and even greater than those that result from directly viewing
the sun. Permanent blindness can occur.
Thermal Injury: The most common cause of laser-induced tissue damage is thermal damage (burn), where the
tissue proteins are denatured by the temperature rise that follows absorption of laser energy.
Such burns are generally associated with lasers that operate at exposure times greater than 10 microseconds
and in the wavelength region from near ultraviolet to far infrared (0.315 mm - 103 mm).
The hazards associated with skin exposure are of less importance than eye hazards; however, with the expanding
use of higher-power laser systems, particularly ultraviolet lasers, the unprotected skin of personnel may be
exposed to extremely hazardous levels of beam power if the laser is used in an unenclosed system design.
Laser Pointers
Operate all Class II and Class IIIA laser pointers used in seminar and classroom presentations according to the
following guidelines:
●
Do not stare into the laser beam.
●
Do not intentionally aim the pointer beam at yourself or another person, particularly in the facial area.
●
Direct the beam toward the screen and away from the audience.
●
Turn off the beam when the pointer is not in use.
●
Do not direct the laser beam at mirror-like surfaces.
19