What mask protects the respiratory system from inhalation of hazardous fumes?

N95 respirators and toxic gases or vapors

09.15.2008

Inhaltsverzeichnis Show

N95 respirators and toxic gases or vapors
N95 respirators and toxic gases or vapors
1. What is it for?
2. How do I decide which respiratory protective equipment to recommend?
3. What types are available?
4. What are its limitations?
5. Where must you wear respiratory protection?
6. How do I use it?
7. How do I look after it?
What masks protect against fumes?
What type of respiratory protection is required to protect against toxic fumes or gases?
Which type of mask has adequate respiratory protection from exposure to hazardous drugs?
What offers the best protection against respiratory hazards?

N95 respirators and toxic gases or vapors

From the Massachusetts Nurse Newsletter
September 2008 Edition

By Thomas P. Fuller, ScD, CIH

There is a common misunderstanding in health care that the N95 respirator can protect workers from gases and vapors. This is completely false. The N95 offers no protection from exposure to any chemical odors, gases or vapors that one would typically experience in a hospital or health care setting.

N95 respirators use a filter of densely woven fibers that can stop aerosol particles through impaction, interception and diffusion as the air being breathed in passes the mesh. They are 95 percent efficient in stopping particles down to about 0.1 micrometers (microns) in diameter. So they work well on tuberculosis, and other bacteria, that range in size from about 0.3 to 20 microns.

Gas molecules, however, range in size from only 0.0003 - 0.006 microns. As a result, gases like oxygen, chlorine, hydrogen sulfide and ammonia can all pass freely in the spaces between the fibers in an N95 mask.

The recommendation to use an N95 respirator to reduce the impact of a chemical gas exposure is comparable to the use of a placebo in patient care. Any improvements in conditions are only perceived and are not real.

In order to remove gases from the air they must be either absorbed or adsorbed by a filter media. Absorption occurs when a gas or vapor penetrates a solid structure (like charcoal) and gets “trapped” in the constituent molecules, atoms and ions of the structure. Adsorption is a phenomenon where the gas or vapor interacts with the outer surface of a solid structure through either van der Walls attraction or a combination of chemical interactions.

Workers in indutriddifferent industries are exposed to thousands of different airborne agents. The selection of the appropriate respirator for the hazardous airborne agent is a complex process and should only be done by a qualified industrial hygienist who thoroughly understands the toxic properties of the agents, the workplace levels and safe or regulatory limits of exposure, and the protective capabilities of the respirator.

Any employer with hazardous airborne working conditions is required by the Occupational Safety and Health Administration (OSHA) to have a written respiratory protection program. The program requires that only knowledgeable and competent professionals implement the program, to include assessment of the specific hazards, selection of the respirator appropriate to protect the workers, medical clearance, fit-testing, and worker training. Just like only certain glove materials are protective for only certain chemicals, respirators must be selected in accordance with the airborne hazards and concentrations in the workplace. And just like physicians and nurses have the responsibility to prescribe and administer medicines safely and competently, industrial hygienists have the responsibility to assess workplace exposures and specify appropriate respiratory protection.

For more information visit the Web site of the American Industrial Hygiene Association at aiha.org or contact Dr. Thomas P. Fuller by email at .

1. What is it for?

As part of your duties, you might have to work in areas where you could be exposed to harmful dusts, fumes or gases, or where there is likely to be a deficiency of oxygen (or both). The most likely area will be when rummaging ships.

If you cannot avoid these areas (e.g. by employing different working methods), you must wear respiratory protective equipment.

Many different types are available, from simple dust masks to complex breathing apparatus. This section deals with respirators designed to protect against harmful dust. Breathing apparatus designed to protect against toxic fumes or oxygen deficiency is covered in the next section.

You must make sure that respiratory protective equipment is suitable for the hazards in the area where you are working. You can then decide the types of equipment you need to use (see the next section). To find out whether the equipment is suitable, you should ask:

Is the atmosphere safe to breathe without respiratory protective equipment?; and
Is the substance contaminating the air a dust, gas or vapour?

Advice may also be available from experts. The section on hazardous substances gives advice on examination of such substances.

3. What types are available?

The respirators used in many administrations purify the air by drawing it in through a filter which removes harmful substance(s). Various types of filter are available, depending on the hazards you are likely to encounter.

It is essential you choose the appropriate type and filter. Using the wrong type can be very dangerous because it won’t protect you.

WARNING: Equipment must be fitted properly and training must be provided before use.

	Dust mask	A basic dust mask will provide LIMITED protection in dusty environments. Ensure it is fitted closely to the nose and around the chin. It may not provide protection against fine dust or nano-particles. It will NOT provide protection against vapours and gasses. SINGLE USE ONLY
	Half face filter mask	TRAINING AND PROPER FITTING REQUIRED. Uses replaceable filters. Appropriate filter must be chosen for the conditions. It will NOT provide protection against vapours and gasses. Filters must be replaced regularly and the condition of the mask checked. Additional Eye Protection may be necessary.
	Full face filter mask	TRAINING AND PROPER FITTING REQUIRED. Uses replaceable filters. Appropriate filter must be chosen for the conditions. Filters must be replaced regularly and the condition of the mask checked.
	Powered air purifying respirator	TRAINING AND PROPER FITTING REQUIRED. Creates a positive pressure flow of clean air around the face using a pump to filter the air. Uses replaceable filters. Appropriate filter must be chosen for the conditions. Filters must be replaced regularly and the condition of the mask checked.
Where there is gas or vapour and or limited oxygen respiratory protection will not protect you. You must not enter such areas unless trained and equipped with Breathing Apparatus
	Self-contained breathing apparatus	TRAINING AND PROPER FITTING REQUIRED. Creates a positive pressure flow of clean air around the face using a tank of pressurised air. See Breathing Apparatus for more information.

Full face mask and powered full face respirator can provide protection again vapours and gases – depending on the type of the filter used.

4. What are its limitations?

Respirators provide no protection against toxic gases, and are mainly designed to protect you against harmful or nuisance dusts. They are only as good as the filter material — if it is missing, damaged or worn the respirator will not protect you.

Use in high temperatures: You may find some types of respirator uncomfortable if you wear them for long periods in a warm environment.
Using dust respirators: Always check that you have the appropriate respirator and filter before you enter any dusty atmosphere. Remember: the area could also be deficient in oxygen — the respirator will not protect you from this.

The filters in respirators will eventually become clogged with dust and then breathing will be more difficult. Replace the filters (outside the contaminated atmosphere) as recommended by the manufacturer.

Remember: some respirators with cartridge filters also have a recommended ‘maximum use’ period. Make sure you know what it is and follow it.

5. Where must you wear respiratory protection?

You should wear respirators whenever you have to work in dusty atmospheres. Managers should determine whether respirators are required following their health and safety risk assessments.

The respiratory protection in combination with full body protection and appropriate gloves should be worn also when handling with dangerous goods or the chemicals with unknown composition.

6. How do I use it?

It is important that you know how to use all forms of respiratory protection. Your manager should give you training which covers:

what the hazard is and what could happen to you if you do not use the equipment;
why the respirator chosen is appropriate to the hazard (i.e. what it protects you against);
the limitations of the equipment;
how to use the equipment; and
practice in handling, fitting and testing the equipment.

The fit of the face-piece is particularly important. It must be airtight. For this reason, full-face respirators are not suitable for officers with a beard or who wear spectacles.

Test the fit of the face-piece before use, as follows:

close the inlet valve;
inhale gently so the face-piece collapses slightly, and hold your breath for 10 seconds;
if the face-piece remains in the slightly collapsed position, and no inward leakage of air is detected, the fit is satisfactory;
if you do detect any leakage, adjust the face-piece and repeat the test. If you still notice a leakage, the face-piece is probably faulty and must not be used. (Do not over-tighten the straps around your head — they should only be adjusted so as to give an airtight fit to the face);
for hygiene reasons, it is better if each respirator supplied is used exclusively by a single officer. It should also be cleaned and disinfected immediately after use.

7. How do I look after it?

Storage: You should store the respirator in its carrying case, a clean metal box or a clean polythene bag.

Inspections: You must inspect all respirators before use, as follows:

Face-piece	Check for cracks, punctures or other damage
Harness	Check that the stitching is sound
Valves	Check for damage and make sure that they move freely and that the mountings are secure
Filters	Check that they are undamaged and securely attached and that they are the right type for the materials to be encountered
Other components	Check that they are securely fixed and undamage

Replacing filters: Replace filters in accordance with the manufacturer’s instructions or sooner if you have difficulty breathing when using the respirator. Spare filter cartridges must be stored in a dark, dry place at room temperature. Unused filters have a shelf life and must not be used beyond the marked expiry date.

Cleaning: The respirator must be kept clean and disinfected and must be visually inspected after each use. Do not wash the filter — you should dismantle the equipment and wash the rest with soap and water (not detergents or solvents). Clean and check the exhalation valve and disinfect the whole unit with a mild, household fluid. Do not replace the filter until the unit is thoroughly dry — but keep it out of direct sunlight.

Servicing and repairs: Servicing and repairs must be carried out only by experienced people, normally the manufacturer. Do not attempt to carry out even minor repairs, except for replacing filter cartridges.

What masks protect against fumes?

N95 respirators are designed to protect against particulate matter such as dust, fumes, mists, aerosols, and smoke particulates.

What type of respiratory protection is required to protect against toxic fumes or gases?

Chemical Cartridge/Gas Mask Respirator: Gas masks are also known as "air-purifying respirators" because they filter or clean chemical gases out of the air as you breathe. This respirator includes a facepiece or mask, and a cartridge or canister. Straps secure the facepiece to the head.

Which type of mask has adequate respiratory protection from exposure to hazardous drugs?

The primary airborne exposure concerns are particulates and aerosols, for which NIOSH approved particulate respirators can help reduce exposures to hazardous drugs.

What offers the best protection against respiratory hazards?

GAS MASKS. Gas masks are more effective than chemical cartridge respirators against high concentrations of toxic gases. The chemical filter in the gas mask removes toxic vapors and particles from the air, such as fumigants for buildings.