For which EPA level of chemical-protective clothing is the use of an APR permissible?

The use of an Air-Purifying Respirator (APR) is permissible with Level C chemical-protective clothing because this level is designed for situations where there is a known airborne concentration of specific contaminants, but the levels are not high enough to require the use of a self-contained breathing apparatus (SCBA). Level C offers a lesser degree of protection compared to Levels A and B, which require full respiratory protection due to the potential for high levels of exposure or unknown contaminants.

In Level C, a proper understanding of the specific chemical hazards present, combined with effective monitoring, allows for the use of respirators that filter the contaminants from the air, making APRs suitable in these environments. Additionally, Level D is primarily for situations with no known hazards and does not typically involve the use of APRs or any respiratory protection, thereby distinguishing Level C as the correct choice for those scenarios where APRs can be appropriately used.