Air-Purifying Respirators and Hoods
Overview
This module introduces
respiratory protection in the form of air- purifying respirators (APR) and
hooded respirators. The focus is toward
disaster site workers who may be exposed to chemical, biological, radiological,
nuclear agents (CBRN), or airborne particulates that may be found at disaster
sites. Remediation that involves
demolition will also generate airborne hazards.
Objectives
After completing
this module, the participant will be able to:
- Identify
if an air-purifying respirator is approved for CBRNE use by NIOSH.
- List
the limitations of APRs.
- List
the types of APRs.
- Describe
some respiratory hazards.
- Explain
what must occur before a user can wear a respiratory protection device
such as an APR.
Respiratory Protection and CBRNE Agents
A terrorist has attacked your facility, causing an explosion that releases
chemicals into the air inside and around the facility. Do you have respirators on hand to protect
emergency responders and the rest of the work force trying to escape?
The answer to that question depends on whom you ask and, to a certain
degree, on the type of facility and where it is located. Terrorists are likely to strike near large
population centers, but they also may target a remote chemical facility, for
instance, because of the availability of toxic industrial materials or
chemicals that could be used in the attack.
No town, city, or state is immune.
Even places that have some level of protection or shield and cannot say,
'It won't happen here.”
Terrorists potentially have numerous chemical, biological, radiological, nuclear
and explosive/energetic (CBRNE) agents at their disposal. The only limitation is the ingenuity of the
terrorists who design the attack when they are motivated, have the opportunity,
and have a target.
NIOSH Certification
There is no universal type of respirator that is effective against all CBRNE
threats, according to respirator manufacturers and the U.S. government, but development of
such products is under way by respirator manufacturers. The military for years has worked at
providing soldiers with respiratory protection in the event of a terrorist
attack. The technology is available for
industrial use, and NIOSH is working to develop criteria to certify respirator
products that will protect against CBRNE agents.
A debate exists as to whether the right kinds of respirators for CBRNE
agents already are available. The
certification that NIOSH is developing will not be a magic bullet. There won't be one respirator that will do
everything.
NIOSH in May 2003 certified the first self-contained breathing apparatus
(SCBA) for use against CBRNE agents. In
June, stakeholders met in Pittsburgh
to begin establishing certification criteria for full-face, air-purifying
respirators. The agency also planned to
offer certification for escape respirator hoods and powered air-purifying
respirators over the next year or two. The
goal is to certify as many products as possible against virtually all CBRNE
hazards.
In any event, terrorist or industrial, you don't necessarily know what you'll
find. You could encounter any of the
toxic industrial materials, as well as chemical warfare agents. The respiratory protection you're offering
needs to have some assurance it is capable of meeting this wide spectrum of
hazards.
On-Site Chemical or Warfare Agent
Business and industry complying with 29 CFR 1910.134, OSHA's respiratory
protection standard for general industry, may be more prepared than they think if
a terrorist used large quantities of existing chemicals to fuel an attack. Facilities with compliant respiratory
protection programs likely are prepared for the release of existing chemicals,
whether by accident, terrorist activity, or disaster.
Accidental releases of chemicals, however, may be at lower concentrations
than releases caused by terrorists or natural disaster. Today, media contained in canisters exists
that will filter out many toxic industrial materials, but not at the potential
concentrations that NIOSH believes might happen. NIOSH is working with the U.S. Army Soldier
and Biological Chemical Command (SBCCOM)
on hazard mapping to determine potential concentrations if particular chemicals
are released by terrorists. If you don't
know the concentration, you're pretty hard-pressed to say a particular
respirator filter canister will provide protection.
While the use of WMD agents such as sarin or mustard gas is less likely,
respiratory protection for these hazards is harder to prepare for because of
not knowing which agent(s) a terrorist will use. NIOSH lists 40 WMD-type
hazards, including several biological, chemical, nerve and choking agents. Respirators typically are stored and
distributed as needed; however, respirators for terrorist response need to be
readily available.
What if the threat of a terrorist attack is thought to be extremely low at a
facility that has had no need for respiratory protection in the past? The facility needs to assess whether a threat
exists and determine if respiratory protection is feasible and practical. Unless there's a credible threat, you can't
have respiratory protection available for everybody at a low-risk plant. You need to look at the level of risk and the
potential. If the potential is extremely
low, you may not need to do anything. If
the risk is high enough, however, there are steps to take to protect workers.
Responding or Escaping
The type of respirator protection needed in the event of a terrorist attack or
disaster event depends on the type of hazard present and whether workers are
emergency responders or are part of the work force trying to escape. Each scenario calls for a specific type of
protection.
Responding
For workers who are first responders, wearing an SCBA with an encapsulated
suit is a must. If there is a question as to what CBRN agent was used in the
attack, whereas the disaster site worker who will respond at a later time to
assist or clean up will have the necessary information for proper respirator
selection. Finding out later that a
respirator was inadequate could prove fatal.
The job of first responders entering an unknown environment is to assess the
hazards and determine whether subsequent responders will need the same
full-body protection or whether less physically demanding equipment can be used. Keep in mind that respiratory hazards are not
the only concern for responders to a CBRNE scenario. Dermal exposure or physical exposure may be
the limiting factors.
As the responder's level of exposure decreases, certain types of
air-purifying respirators may be adequate. Powered air-purifying respirators also are
candidates for some responders.
Escaping
To protect workers escaping from a terrorist attack, the choice is between a
respirator or an escape hood. Both have advantages
and disadvantages.
Respirators. If escaping from a terrorist attack, only
some filter media will protect workers. Normal
air-purifying respirators won't provide the protection needed to escape from
CBRNE agents in a WMD scenario.
Respirators for use against CBRNE agents will not be effective unless:
·
The hazard in question has been
properly identified.
·
The mask is fitted and used
properly.
·
The product is used in areas
containing sufficient oxygen.
In addition, a tight-fitting respirator will not provide a proper seal for
those with facial hair or who wear glasses.
Escape hoods. Until recently, escape hoods mostly protected
users from smoke inhalation. It's
important that smoke escape hoods not be used for terrorist attacks because
they do not provide adequate protection against CBRNE agents.
NIOSH-approved escape respirators may protect from specific chemicals, such
as chlorine or sulfur dioxide, but not a majority of hazards. Escape respirators with more universal protection
that are NIOSH-approved have become a real need. One type of escape hood contains an internal
half-mask respirator. Other hoods
contain a mouth bit (some with a nose clip) and cartridge or short-term
supplied air.
In addition to filter protection, CBRNE escape hoods need to provide a
tight-fitting neck seal, similar to a tight seal for full-face respirators. The neck seal as an elastic washer that fits
over the head, then contracts to the user's neck size. Long hair needs to fit inside the hood.
Escape respirator devices likely would be used by workers not used to
wearing respiratory protection, so training is needed on how to don the
product. It should include checking to
see if the user might become distressed or claustrophobic. Ensure that the user's neck size will fit the
range, such as 10 to 22 inches, provided by the product. Advantages of escape hoods over full-face
respirators include fewer restrictions for users concerning facial hair and
glasses, an important consideration.
Air-Purifying Respirator (APR)
These respirators remove air contaminants by filtering,
absorbing, adsorbing, or chemical reaction with the contaminants as they pass
through the respirator canister or cartridge.
This respirator is to be used only where adequate oxygen (19.5 to 23.5
percent by volume) is available. APRs
can be classified as follows:
- Combination particulate/gas and vapor
removing respirators, which combine the respirator characteristics of both
kinds of air-purifying respirators.
APRs do have limitations:
- They
do not work for all chemical environments.
- They
cannot be used in an IDLH atmosphere.
- They
can only be used where adequate oxygen exists.
- They
cannot be used for CBRNE agents unless NIOSH approved.
Types
of APRs
Respiratory
protection is of primary importance since inhalation is one of the major routes
of exposure to airborne contaminants.
Respiratory protection devices (respirators) consist of a facepiece
connected to either an air-purifying device (cartridge or canister) or an air
source.
Different types of
facepieces are available for use with the various types of respirators. The types generally used are full facepieces
and half masks. Full facepiece masks
cover the face from the hairline to below the chin. They provide eye protection. Half masks cover the face from below the chin
to over the nose and do not provide eye protection.
Dust Mask
Another type of
APR is a disposable air purifying particulate respirator (dust mask). Dust masks have the same regulatory
requirements as any other APR. They must
be NIOSH approved. Also, employees
wearing dust masks must complete respiratory protection training, undergo
medical surveillance, and be fit tested.
Limitations for
dust masks are the same as any other APR.
They cannot be used in an oxygen-deficient or enriched environment, or
in an IDLH environment. In addition,
they provide protection against a very limited number of specific dusts and
mists.
For initial
disaster site operations, dust masks are NOT recommended. However, during final phase remediation of
the site they may become appropriate. Be
sure to check with your supervisor regarding the proper respirator for you job.
Airline and
Hoods
SARs, sometimes
called airline respirators, provide breathing air independent of the
environment. They consist of facemask
and compressed air supplied by a compressor or remote cylinder.
SARs also have
limitations. The reach limits of the
inline hose not only restrict the distance from the supplied air source, but
also limit the wearer’s movement. Also,
only grade D air can be used as the supplied air source.
NIOSH Filter Classifications
- N -
For solid particulates and non-oil aerosols that do not degrade filter
performance.
- R -
For solid particulates and degrading oil-based aerosols. R filters have
"Use Limitations."
- P -
For solid particulates and degrading oil-based aerosols. P filters have no
"Use Limitations" other than those normally associated with
particulate filters.
Three efficiency levels: 95%; 99%; 99.97%.
Respiratory Hazards
Air contaminants
that pose respiratory hazards can exist in many forms. Employees need to know what these forms are
and their sources for these potential contaminants in order to protect
themselves from exposure. Air contaminant
forms, examples of such forms, and the potential consequences of overexposure
are listed below.
Dusts
Created when
solid material breaks down and gives off fine particles that float in the air
before settling by gravity.
Examples: grinding, crushing,
drilling, blasting, sanding, and milling operations. Overexposure could potentially lead to
pneumocosis or the toxic effects of the material.
Mist
Particles formed
from liquid materials by atomization and condensation processes. Examples:
spraying operations, plating operations, and mixing and cleaning
operations. Overexposure could potentially lead the toxic effects of the
material.
Fumes
Created when
solid materials vaporize under high heat.
The metal vapor cools and condenses into an extremely small particle
with a particle size generally less than one micrometer in diameter. Examples:
welding, smelting, and pouring of molten metal. It is important to note that toxic fumes can
result from the burning of non-toxic substances. Overexposure could potentially
lead to the toxic effects of the material.
Gases
Substances that
are similar to air in their ability to diffuse or spread freely throughout a
container or area. Examples: oxygen, carbon dioxide, nitrogen, helium and
chlorine. Overexposure could potentially lead to the toxic effects of the
material.
Vapors
The gaseous
states of substances that are either liquids or solids at room
temperature. They are formed when solids
or liquids evaporate. Examples: gasoline, paint thinner, degreaser solvents.
Overexposure could potentially lead to the toxic effects of the material.
Respirator Use
Workers who are required to use
respirators must be:
·
Trained
such that they can demonstrate knowledge of at least why the respirator is
necessary and how improper fit, use, or maintenance can compromise its
protective effect
·
Medically
evaluated to determine their ability to safely wear the respirator
·
Fit tested
to assure the respirator will provide adequate wear-time protection
Proper respirator use includes adequate cleaning and inspection, donning,
user seal checks, and doffing.
Cleaning and Inspection
These procedures are provided for
employer use when cleaning respirators. They are general in nature, and the
employer as an alternative may use the cleaning recommendations provided by the
manufacturer of the respirators used by their employees, provided such
procedures are as effective as those listed in 29 CFR 1910.134 Appendix B-
2. Equivalent effectiveness simply means
that the procedures used must accomplish the objectives set forth in Appendix
B-2, i.e., must ensure that the respirator is properly cleaned and disinfected
in a manner that prevents damage to the respirator and does not cause harm to
the user.
Procedures for Cleaning
and Inspecting Respirators
- Remove
filters, cartridges, or canisters. Disassemble facepieces by removing
speaking diaphragms, demand and pressure- demand valve assemblies, hoses,
or any components recommended by the manufacturer. Discard or repair any
defective parts.
- Wash
components in warm (43 deg. C [110 deg. F] maximum) water with a mild
detergent or with a cleaner recommended by the manufacturer. A stiff
bristle (not wire) brush may be used to facilitate the removal of dirt.
- Rinse
components thoroughly in clean, warm (43 deg. C [110 deg. F] maximum),
preferably running water. Drain.
- When
the cleaner used does not contain a disinfecting agent, respirator
components should be immersed for two minutes in one of the following:
1.
Hypochlorite
solution (50 ppm of chlorine) made by adding approximately one milliliter of
laundry bleach to one liter of water at 43 deg. C (110 deg. F); or,
2.
Aqueous
solution of iodine (50 ppm iodine) made by adding approximately 0.8 milliliters
of tincture of iodine (6-8 grams ammonium and/or potassium iodide/100 cc of 45%
alcohol) to one liter of water at 43 deg. C (110 deg. F); or,
3.
Other
commercially available cleansers of equivalent disinfectant quality when used
as directed, if their use is recommended or approved by the respirator
manufacturer.
- Rinse
components thoroughly in clean, warm (43 deg. C [110 deg. F] maximum),
preferably running water. Drain. The importance of thorough rinsing cannot
be overemphasized. Detergents or disinfectants that dry on facepieces may
result in dermatitis. In addition, some disinfectants may cause
deterioration of rubber or corrosion of metal parts if not completely
removed.
- Components
should be hand-dried with a clean lint-free cloth or air-dried.
- Reassemble
facepiece, replacing filters, cartridges, and canisters where necessary.
- Test
the respirator to ensure that all components work properly.
Donning and Doffing
A respirator must be put on and worn properly if it
is to fit and offer effective protection. Always inspect your respirator prior
to donning. Donning instructions, found on or in each respirator package,
should be fully explained and demonstrated to the wearer by a competent
person. Once proper donning and
adjustment procedures are understood, each wearer will complete the same
procedure as trained prior to respirator use. Users must be medically evaluated
before donning the respirator and being fit tested.
User Seal Checks
The individual who uses a
tight-fitting respirator is to perform a user seal check to ensure that an
adequate seal is achieved each time the respirator is put on. Either the
positive and negative pressure checks listed below, or the respirator
manufacturer's recommended user seal check method shall be used. User seal
checks, however, are not substitutes for qualitative or quantitative fit tests.
Facepiece Positive and/or Negative Pressure Checks
Positive
pressure check.
Close off the exhalation valve and exhale gently into the facepiece. The face
fit is considered satisfactory if a slight positive pressure can be built up
inside the facepiece without any evidence of outward leakage of air at the
seal. For most respirators this method of leak testing requires the wearer to
first remove the exhalation valve cover before closing off the exhalation valve
and then carefully replacing it after the test.
Negative
pressure check.
Close off the inlet opening of the canister or cartridge(s) by covering with
the palm of the hand(s) or by replacing the filter seal(s), inhale gently so
that the facepiece collapses slightly, and hold the breath for ten seconds. The
design of the inlet opening of some cartridges cannot be effectively covered
with the palm of the hand. The test can be performed by covering the inlet
opening of the cartridge with a thin latex or nitrile glove. If the facepiece
remains in its slightly collapsed condition and no inward leakage of air is
detected, the tightness of the respirator is considered satisfactory.
Manufacturer's Recommended User Seal Check
Procedures
The respirator manufacturer's
recommended procedures for performing a user seal check may be used instead of
the positive and/or negative pressure check procedures provided that the
employer demonstrates that the manufacturer's procedures are equally effective.
