Types of Respirators
Quick Tips #275
Respirators are among the most important pieces of protective equipment for working in hazardous environments. Selecting the right respirator requires an assessment of all the workplace operations, processes and environment. The identity of the hazard and its airborne concentrations need to be determined before choosing a respirator. This assessment should be done by experienced safety personnel or by an industrial hygienist.
Several agencies are responsible for researching and establishing contaminant exposure limit levels for hazardous substances. The American Conference of Governmental Industrial Hygienists (ACGIH) is a voluntary organization of safety professionals that develops and reviews exposure limit values. ACGIH results are based on animal, human and industrial studies. The National Institute for Occupational Safety and Health (NIOSH) is a federal agency that conducts research on safety and health concerns. NIOSH is responsible for developing and revising recommended exposure limits for hazardous substances. The recommendations are then transmitted to the Occupational Safety and Health Administration (OSHA), a federal agency in the Department of Labor which has safety, regulatory and enforcement authority over most industry and business.
Types of Respirators
Once a workplace assessment has been completed and engineering controls have been ruled out, the respirator selection process can begin. There are several different respirators for various hazard situations. The respirator you choose should provide protection against the hazard for which it was designed, in addition to being NIOSH approved.
Air-purifying respirators can be either filtering facepiece, full-face or half masks with mechanical or chemical cartridges to filter dusts, mists, fumes, vapors or gases. They are available in three types: disposable, reusable, and disposable/reusable.
Filtering facepiece respirators are meant to be disposable, one time use devices. These are used to filter out particulate matter only.
Disposable air-purifying respirators are intended to be used once or until the cartridge expires. The cartridges are permanently attached and have no replacement parts.
Reusable air-purifying respirators use both replaceable cartridges and parts. They can be full face or half mask respirators. NOTE: The replaceable cartridges and parts must be from the same manufacturer to retain a NIOSH approval.
Gas masks are designed for slightly higher concentrations of organic vapors, gases, dusts, mists and fumes. The volume of sorbent used as the medium is higher than a chemical cartridge.
Powered air-purifying respirators use a blower to pass the contaminated air through a filter. The purified air is then delivered into a mask or hood. They filter dusts, mists, fumes, vapors and gases, just like ordinary air-purifying respirators.
Air-purifying respirators cannot be used in oxygen-deficient atmospheres, which can result when another gas displaces the oxygen or consumption of oxygen by a chemical reaction occurs. Oxygen levels below 19.5% require either a source of supplied air or supplied-air respirator protection. Levels below 16% are considered to be unsafe and could cause death.
Supplied-air respirators provide the highest level of protection against highly toxic and unknown materials. Supplied air refers to self-contained breathing apparatuses (SCBAs) and air-line respirators.
SCBAs have a limited air supply that is carried by the user, allowing for good mobility and fewer restrictions than air-line respirators.
Air-line respirators have an air hose that is connected to a fresh air supply from a central source. The source can be from a compressed air cylinder or air pump that provides at least Grade D breathing air.
Emergency escape breathing apparatuses (EEBAs) provide breathing air for 5, 10 or 15 minutes depending on the unit. These are for emergency situations in which a worker must escape from environments immediately dangerous to life or health (IDLH).
Respirators can be made from a variety of materials. The most popular facepiece materials are silicone, neoprene, and rubber. In general, rubber and neoprene are rigid, durable materials. Silicone is preferred for its comfort, flexibility and ease in cleaning. Full-face respirators are available with six-strap harnesses or ratchet suspensions. The harness type can be worn with a hard hat, but ratchet suspensions are generally easier to adjust, making donning and doffing easier.
Various features are available to help you customize respirators to suit your employees and the specific hazards they encounter. For example, nose cups reduce lens fogging and lens covers protect the lens from paint, minor chemical splash and scratches.
Spectacle kits are needed when using prescription corrective lenses. The frame mounts into full-face masks, and the prescription lenses are made by the wearers' optometrist. This allows the wearer to maintain a proper fit and still wear prescription lenses.
To determine the proper cartridge for air-purifying respirators, either contact a safety professional or consult the Material Safety Data Sheet of the substance that needs to be filtered. All cartridges are assigned a color designating the type of contaminant they will filter:
Cartridge Color: Contaminant
White: Acid gas
Black: Organic vapors
Green: Ammonia gas
Yellow: Acid gas and organic vapors
Purple: Any particulates - P100
Orange: Any particulates - P95, P99, R95, R99, R100
Teal: Any particulates free of oil - N95, N99, or N100
The medium used as the filter is usually activated carbon. The adsorption capacity of the filter is limited.
Particulate Filter Classification
NIOSH published new public health regulations and upgraded test requirements for the certification of particulate filters in the summer of 1995. Currently, most filters meet these test requirements, giving you a large selection from which to choose. These filters also meet the criteria set by the Centers for Disease Control (CDC) for protection against Tuberculosis.
The nine classes of filters are broken down into three series: N, R, and P. Each series has three efficiency levels: 95%, 99%, and 99.97%. The efficiency levels are determined by testing the filter with either sodium chloride (NaCl) or dioctyl phthalate (DOP) until a maximum load of 200 mg is reached. Sodium chloride is a mildly degrading material, while dioctyl phthalate is highly degrading. The difference between the three series of filters is found in their limitations and the way they are tested.
The N series filter is tested with NaCl, and is used in environments free of oil aerosols. The R series is tested with DOP. A respirator with this series filter should only be worn for one work shift. The P filter is also tested with DOP, but the test doesn't stop at a 200 mg load. The test continues until there is no further decrease in efficiency at the 95%, 99%, or 99.97% level.
Employers are required to fit test any employee who needs to wear a respirator. This includes dust/mist respirators. Fit testing is a requirement of 29 CFR 1910.134 (See Quick Tips #140: Respirator Fit Testing Requirements and Procedures).
Anytime a respirator is used in the workplace, a written program must be established. A program outlines very specific procedures for respirator use in all situations. The program can vary in format, but must contain specific information on topics ranging from buying a respirator to employee training.
Ongoing workplace monitoring ensures that employees are adequately protected. Any change in the workplace operations may change the levels of contaminants or introduce new hazards. If a change occurs, the entire respirator program should be re-evaluated to determine its effectiveness.
One exception, is that employers are not required to include in a written respiratory protection program those employees whose only use of respirators involves the voluntary use of filtering facepieces. Voluntary use guidelines are found in 29 CFR 1910.134 Appendix D.
Commonly Asked Questions
|Q.||What are nuisance levels?|
|A.||Nuisance levels refer to concentrations of contaminants below the OSHA permissible exposure level.|
|Q.||What is the shelf life of a cartridge?|
|A.||Cartridges can have a limited or indefinite shelf life. Contact the manufacturer of the cartridge for specific information on the cartridge shelf life.|
|Q.||What does HEPA stand for?|
|A.||High efficiency particulate absolute. HEPA filters remove from air 99.97% or more of particles having a diameter of 0.3 microns.|
American National Standards Institute
11 W. 42nd Street
New York, NY 10036
ANSI Z88.2-1992, American National Standard for Respiratory Protection.
Blackwell, Daid S., Rajhans, Practical Guide to Respiratory Usage in Industry, Boston, 1985.
Hansen, Doan J., The Work Environment. Occupational Health Fundamentals, Chelsea, 1991, pp. 304–308.
Plog, Barbara A., Fundamentals of Industrial Hygiene, National Safety Council, 1988, pp.521–568.
Find even more information you can use to help make informed decisions about the regulatory issues you face in your workplace every day. View all Quick Tips Technical Resources at www.grainger.com/quicktips.
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