137
RESPIRATORS 

Respirator protection is an important and necessary method used to protect persons engaged in all forms of asbestos work from unnecessary exposure to asbestos fibers. 

Respirators can be broadly categorized as Negative-pressure types or Positive-pressure types. In a negative-pressure respirator, one or more air purifying filters or cartridges are attached via an inhalation valve to a tight-fitting rubber facepiece. The negative air pressure created by inhalation draws the contaminated air through the purifying filter to the workers. Because of this, a leak-proof seal between the facepiece and the worker's face is absolutely essential for proper protection. Leaks may be caused by improper fit, the presence of facial hair or foreign substances under the sealing surface, or cracked or damaged seals, valves or cartridges.

The air purifying cartridges used in negative pressure respirators offer considerable resistance to the free flow of air. During inhalation (the negative pressure phase), contaminated air will quite readily bypass the cartridge and follow the path of least resistance through any leaks which are present, thereby exposing the worker. Because of this, negative-pressure respirators provide less protection than all other types of respirators.

Negative-pressure respirators are also known as air purifying respirators (APR). They offer no protection against oxygen deficiency, and generally have the lowest protection factor rating of all respirator types. Although OSHA regulations permit the use of half mask dual HEPA cartridge APRs for asbestos exposure up to ten times the permissible exposure limit of .2 fibers per cubic centimeter, it is highly recommended that their use be limited to operations where actual asbestos levels would be expected to be below detectability; such as: building inspection, glove bag removals, pre-abatement preparations, and final cleaning.

Powered Air Purifying Respirators (PAPR), Supplied Air, and Self-Containing Breathing Apparatus (SCUBA) are all positive-pressure respirators.

Powered Air Purifying Respirators (PAPR) use the same type of cartridges and filters as APRs to clean the air. PAPRs employ a portable, rechargeable battery pack and blower to force the contaminated air through the cartridge and supply the filtered air to the worker's breathing zone. PAPRs are available in both tight-fitting and loose-fitting styles. Because the air is being drawn from the immediate work area, they too offer no protection against oxygen deficiency. Nominal protection factors for PAPRs fall between that of APRs and supplied-air types.

Both APRs and PAPRs employ either chemical cartridges or mechanical filters. The type of cartridge, and hence the particular hazardous substance for which it provides protection is identified by labeling and a standardized color coding of the cartridge. 

The specific cartridge to be used for protection against exposure to asbestos dust is a 'High Efficiency Particulate Air" (HEPA) filter cartridge, which has been assigned the code color magenta (purple). Regardless of manufacturer, HEPA cartridges are identified by both labeling and the code color magenta. Some manufacturers color the entire cartridge case magenta, some use a magenta stripe, while others print the label in magenta ink on a black background. Supplied Air Respirators, also called Type C Respirators, supply clean air via a hose to the face mask from outside the work area and they do offer protection against oxygen deficiency.

Self-Contained Breathing Apparatus employs air tanks which are worn by the worker to supply the air. They are seldom used in asbestos work.

More information on the respiratory protection requirements as they apply to asbestos abatement work can be found in the United States Environmental Protection Agency booklet, "Respiratory Protection," OSHA 3079 which can be obtained from your regional federal OSHA office. Relevant regulations governing the use of respirators are found in the Code of Federal Regulation 29 CFR 1910.134 and 29 CFR 1926.103.


(published October 1988)