A respirator equipped with an end-of-service life indicator is approved for which contaminant?

A respirator with an end-of-service life indicator (ESLI) is designed to provide a visual or audible signal that indicates when the filter or cartridge has reached its effective life limit for a specific contaminant. This feature is crucial for ensuring that users are aware of when the respirator may no longer provide adequate protection.

Among the options provided, carbon monoxide is a contaminant that presents unique challenges for detection, as it is colorless and odorless. An ESLI would be particularly beneficial for such gases because it helps prevent exposure to dangerous levels of the contaminant without users relying solely on their senses, which could fail them in the case of carbon monoxide exposure.

Conversely, other gases listed, such as chlorine and hydrogen sulfide, typically have distinct sensory indicators (strong odors or colors) that can alert users to their presence before reaching dangerous levels. In contrast, carbon dioxide is generally not a primary concern for respiratory protection, as it is not typically classified as a toxic gas at normal atmospheric concentrations, thus not requiring a respirator to have an ESLI.

This means that the approval of respirators with ESLIs aligns closely with the need for safeguarding against gas exposure that lacks physical sensory warnings, making carbon monoxide the most relevant contaminant in the