ESLIs for Respirator Cartridges/Canisters


End-of-service-life is when a respirator can no longer provide the expected level of protection to the user. Your filter medium is clogged. Breathing while wearing the respirator may have become difficult; or the sorbent, when protecting against gases or vapors, has reached its capacity and can no longer capture and retain harmful contaminants. Or, this may be when the respirator becomes damaged, soiled, or its integrity is no longer intact.

In a NIOSH blog, according to the Occupational Safety and Health Administration’s (OSHA), Respiratory Protection Standard 29 CFR 1910.134, employers are required to provide a respirator cartridge change schedule.  A change schedule is the part of the written respirator program which says how often cartridges should be replaced and what information was relied upon to make this judgment.

A cartridge’s useful service life is how long it provides adequate protection from harmful chemicals in the air. The service life of a cartridge depends upon many factors, including environmental conditions, breathing rate, cartridge filtering capacity, and the amount of contaminants in the air. It is suggested that employers apply a safety factor to the service life estimate to assure that the change schedule is a conservative estimate.

Some gas- and vapor-removing air-purifying respirators are also equipped with passive end-of-service-life indicators (ESLIs). The ESLI is usually specific to only one contaminant. The ESLI gives the wearer an indication, often a color change, that the contaminant will no longer be sufficiently removed by the cartridge/canister and that the cartridge/canister should be replaced.

However, ESLI could be affected by the conditions in the work environment. The OSHA regulation exists to ensure the filter change happens in the event that the ESLI doesn’t function properly. The ESLI can be used as a change indicator if conditions allow, which adds a safety margin to the change schedule. The indicator will change color prior to the end of the cartridge life.

If conditions do not allow the ESLI to function properly or if multiple gases are present, and the ESLI is an indicator for only one of those gases, OSHA requires that a change schedule be the primary method of keeping track of your cartridge’s/canister’s lifespan.

Additionally, OSHA has mandatory use limits and exposure limits for certain substances like acrylonitrile, benzene, butadiene, formaldehyde, vinyl chloride, and methylene chloride. Workers depending on respiratory protection who are exposed to any of these contaminants at or above the OSHA Permissible Exposure Limit (PEL) must change cartridges/canisters according to OSHA’s requirements.

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