Do respirators have end-of-service-life indicators on them?

Yes. Some do, for others like the N95 the “indicator” may be the appearance, whether the respirator is damaged, contaminated with visible blood or body fluids, or misshapen. For other types of respirators there are specific indicators integral in the device. All self-contained breathing apparatuses have an alarm that tells the wearer that he/she is going to run out of air from his cylinder and he/she must leave the contaminated area. Some gas- and vapor-removing air-purifying respirators are also equipped with end-of-service-life indicators (ESLI). The ESLI are usually specific to only one contaminant. The ESLI gives the wearer an indication, often a color change, that the contaminant will no longer be able to be removed by the cartridge or canister and that the cartridge or canister should be replaced.