Choosing between Air-purifying and Atmosphere-supplying Respirators

Choosing the right equipment involves taking into consideration not only the site hazards, but which of the available pieces of respiratory protection will serve the job the best. For example, an air-purifying respirator (which uses filters or sorbents to remove harmful substances from the air) does not supply oxygen to workers. Therefore, an air-purifying respirator could never be used in oxygen-deficient atmospheres.

Atmosphere-supplying respirators, on the other hand, supply air to the user and are better suited for oxygen-deficient atmospheres or IDLH situations. However, in some cases there is a time limitation for use of these devices: oxygen may run out of the supply pack. Therefore, employers must always consider the time required to perform the task when selecting an atmosphere-supplying respirator. If the task requires a long length of time, an atmosphere-supplying respirator that supplies breathable air from an air compressor through an air line is the safest option.

OSHA additionally suggests that employers note the following when selecting an air-purifying respirator: "SARs eliminate the need for concern about filter breakthrough times, change schedules, or using end-of-service-life indicators (ESLI) for airborne toxic materials."

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