Types of Respirators
Respirators are designed to protect only against specific types of substances, in certain concentrations, and must be matched to the user, job, and contaminant. This section program will discuss two categories of respirators including:
AIR-PURIFYING RESPIRATORS (APRS)
- Particulate removing
- Vapor/Gas removing
- Combination
SUPPLIED AIR RESPIRATORS (SARS)
- Self-Contained Breathing Apparatus (SCBA)
- Supplied Air Respirator (Air-line)
AIR-PURIFYING RESPIRATORS
- Air-purifying respirators (APRs) remove contaminants from the atmosphere; they must be used only in atmospheres with sufficient oxygen (> 19.5% AND < 23.5 %) and within specified hazard concentration limitations of the specific device.
General Limitations of Air-Purifying Respirators
Air-purifying respirators may not be used for protection in the following circumstances:
- Air-purifying respirators do not provide effective protection against certain gaseous materials. Section 3.1.1.2 discusses specific limitations of APRs in a gas/vapor contaminated environment.
- The maximum contaminant concentration against which an air-purifying respirator will protect is determined by the design efficiency and capacity of the cartridge, canister, or filter and the face-piece-to-face seal on the user. For gases and vapors, the maximum concentration for which the air-purifying element is designed is specified by the manufacturer or is listed on labels of cartridges and canisters. For assistance in determining maximum contaminant concentrations, contact the Department of Environmental Health and Safety
- Air-purifying respirators will not provide the maximum design protection specified unless the face piece is carefully fitted to the wearer's face to prevent inward leakage. The time period over which protection is provided is dependent on canister, cartridge, or filter type; concentration of contaminant; humidity levels in the ambient atmosphere; and the wearer's respiration rate.
- The proper type of canister, cartridge, or filter must be selected for the particular atmosphere and conditions. Air-purifying respirators may cause discomfort due to the noticeable resistance in inhalation.
Specific Limitations for Air-Purifying Particulate-Removing Respirators
- Use for protection against nonvolatile particles only. These respirators offer no protection against gases or vapors.
- These respirators are not for use in an atmosphere immediately dangerous to life or health (IDLH).
- Do not use air-purifying particulate-removing respirators in oxygen-deficient atmospheres.
Specific Limitation for Air-Purifying Gas/Vapor-Removing Respirators
Do not use air-purifying vapor/gas removing respirators with airborne chemicals that have "poor warning properties."
- Appendix G contains a list of gaseous materials for which air-purifying respirators should not be used.
- Do not use air-purifying vapor/gas-removing respirators in atmospheres with unknown chemicals. Do not use in atmospheres with unusually high concentrations of a known chemical.
- Do not use air-purifying vapor/gas-removing respirators in oxygen-deficient atmospheres.
Supplied Air Respirators
Atmosphere-supplying or Supplied Air Respirators (SAR) deliver breathing-air through a supply hose connected to the wearer's face piece. The breathing-air can be provided from a stationary source, i.e., by a compressed air tank (SCBA) or a breathing air compressor (air line)
Atmosphere-supplying respirators are required when there is insufficient oxygen (<19.5 percent), when the concentration of contaminant is too high for an air-purifying cartridge to handle, the toxicity of the material is too hazardous for an air-purifying cartridge, or when required by specific Federal Occupational Safety And Health Administration (OSHA) regulations.
General Limitations
Except for some air-line suits, no protection is provided against skin irritation by materials such as ammonia and hydrogen chloride, or against absorption through the skin of materials such as hydrogen cyanide and organic phosphate pesticides. Use of atmosphere-supplying respirators in an atmosphere Immediately Dangerous to Life or Health (IDLH) is limited to Self-Contained Breathing Apparatus (SCBA) or to those Supplied Air-line Respirators equipped with an "escape" bottle of air.
Note: Oxygen levels exceeding 23.5% (Oxygen Enriched Atmospheres) pose an increased risk of fire and explosion to combustible materials. Respiratory protection devices cannot control hazards of this nature.
Specific Limitations for Self-Contained Breathing Apparatus (SCBA)
Below are some limitations of SCBAs. For specific limitations, consult the owner's manual of the specific make and model of the breathing apparatus.
- The period over which the device will provide protection is limited by the amount of breathing air in the apparatus, the ambient atmospheric pressure (service life of open-circuit devices is cut in half by a doubling of the atmospheric pressure), and the type of work being performed. Some SCBA devices have a short service life (less than 15 minutes) and are suitable only for escape (self-rescue from an irrespirable atmosphere).
- Other limitations of SCBA devices are their weight or bulk, or both, limited service life, and the training required for their maintenance and safe use.
- All self-contained breathing apparatus to be used in an IDLH environment must be rated for at least 30 minutes and must be used in the pressure-demand mode.
Specific Limitations for Supplied-Air Respirators (AIR-LINE)
- Ordinary air-line respirators (no emergency escape air bottle) are limited to use in atmospheres from which the wearer can escape unharmed without the aid of the respirator (i.e., non-IDLH and non-oxygen deficient atmospheres).
- The wearer is restricted in movement by the hose and must return to the respirable atmosphere by retracing his/her route of entry. The hose is subject to being severed or pinched off.
