End Of Service Life Indicator

An End-of-Service-Life Indicator (ESLI) is a device or system in respiratory protective equipment that warns the user when the respirator’s protective element is approaching the end of its effective service life, such as when a sorbent cartridge is nearing saturation or is no longer effective. In CSA respiratory guidance, it is described as a device incorporated into the filtering element to notify the wearer that the element is saturated and no longer useful.

On a manufacturing or shop floor, an ESLI is used to tell workers when to replace a cartridge, filter, or other air-purifying element before breakthrough occurs. This matters in jobs involving solvents, gases, or particulates where the worker cannot rely only on smell or symptoms; the ESLI provides a visual, audible, or other detectable warning tied to the respirator’s remaining protection capacity. WorkSafeBC ties respiratory protection use to manufacturer instructions and storage conditions, and for emergency use requires workers to be informed when expired respirators are used. A worker monitors the ESLI during exposure tasks, and when the indicator shows saturation or loss of effectiveness, the cartridge or filter is removed from service immediately. Supervisors use the indicator as part of the respiratory protection program, along with fit testing, change-out schedules, and hazard assessments.

• ⚠️Relying on ESLI alone without a respiratory protection program; OSHA defines ESLI as only one part of warning the user, and the employer must ensure the respirator is appropriate for the hazard and used within its certified limits.
• ⚠️Using an indicator on the wrong contaminant or exposure scenario; ESLIs are not universally reliable for every gas, vapor, humidity condition, or mixed contaminant environment, and cartridge life can end before the indicator changes if the exposure profile differs from test assumptions.
• ⚠️Ignoring manufacturer instructions or continuing to use expired/damaged equipment; WorkSafeBC requires use in accordance with manufacturer instructions, and allows expired respirators only in emergency last-resort situations with worker notification and proper storage history.