Selecting an air-purifying respirator
When it comes to selecting an air-purifying respirator, chemical cartridges or gas masks are a step up from two-strap disposable air-purifying respirators.
Air-purifying respirators can filter chemical gases and in some cases, particulate as well, out of the air as you breathe. These respirators are comprised of a face piece or mask, filters/cartridges (a filter in a metal shell is called a “canister”), and rugged straps to provide a snug, secure, airtight fit to the entire face.
Air-purifying respirators can be either full-face or half masks, with mechanical or chemical cartridges to filter dusts, mists, fumes, vapors or gases. Air-purifying respirators or masks are generally available in three types:
- Disposable respirators – intended to be used once or until the cartridge expires. Cartridges are permanently attached and have no replaceable parts.
- Reusable respirators – with replaceable cartridges and parts.
- Disposable/reusable respirators – few or no replaceable parts except cartridges.
Within those three main categories are three types of air-purifying respirators:
- Particulate respirators – captures dust, mists and fumes, but will not protect against gas or vapors.
- Combination respirators – normally used when both particulate and gas hazards are present.
- Gas and vapor respirators – does not protect against particulate hazards, but made to protect against specific gases and vapors.
To get the proper respiratory protection when selecting an air-purifying respirator, you must know the proper cartridge to use. Most filter medium is activated carbon, but other materials are used for specific conditions. The absorption capacity of filters is limited, so filters must be replaced in a timely manner.
Workers should consult the Material Safety Data Sheet for the substance that needs to be filtered or contact a safety professional for advice. All respirator cartridges are assigned a color designating the type of contaminant they will filter:
- Olive: Multi-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 oil-free particulate – N95, N99, N100
Notice that there are cartridges that protect against more than one hazard, but there is no “all-in-one” filter that protects against all substances. You must know what hazards you will be working under in order to choose the right filter.
Replaceable cartridges and parts must be from the same manufacturer as the mask body in order to retain NIOSH (National Institute for Occupational Safety and Health) approval.
Any time an air-purifying respirator is used in the workplace as part of a personal protection equipment, a written program must be established to conform to Occupational Safety and Health Administration (OSHA) regulations.
The program can vary in format, but must contain specific information on topics ranging from buying a respirator to employee training. See here an OSHA example of a respirator written program.
Ongoing workplace monitoring ensures construction workers are adequately protected. Any change in workplace conditions 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 to this rule is that written programs are not required when employees use air-purifying respirator voluntarily and not because of a written standard.
When selecting an air-purifying respirator, keep in mind that air-purifying respirators cannot be used in oxygen-deficient atmospheres, which can result when gas displaces the oxygen or oxygen is consumed by a chemical reaction. These conditions require the use of supplied-air respirators.
—By Rob Fanjoy