The evaluation of CBRN canisters for use by firefighters during overhaul

Air-purifying respirators (APRs) have been proposed to provide an additional respiratory protection option for structural firefighters involved in overhaul operations and wildland firefighters, where particulate and aldehyde exposures have been documented. Previous studies (Anthony et al., 2007) developed test methods to evaluate APR cartridges and canisters for use in overhaul activities, where initial findings indicated that multi-gas cartridges may not be effective. This study evaluated the performance of three chemical, biological, radiological, and nuclear (CBRN) canisters (MSA, 3M, and Scott) and one multi-gas canister similar in appearance to CBRN canisters but without CBRN certification (3M FR-64040). Challenge concentrations typical of overhaul exposures were generated by combusting common household materials. Twelve tests were conducted, using random canister selection, where challenge air and air filtered by the canisters were tested. All tests examined penetration of CO; NO(2); SO(2); respirable dust; aldehydes, including formaldehyde, acrolein, and glutaraldehyde; and hydrogen cyanide. Six of the tests also investigated naphthalene, benzene, and hydrogen chloride, but challenge concentrations from the simulated overhaul smoke were near the limit of detection (LOD) and were two orders of magnitude below short-term or ceiling concentrations of concern and were eliminated from further study with the combustion materials used in this study. In all tests, an irritant index was computed to evaluate the aggregate penetration of contaminants in the smoke mixture, using 15- and 30-min occupational exposure limits as well as assessing individual penetrations. In all cases, the challenge concentration irritant index exceeded unity, ranging from 2.3 to 21. For all 12 tests, the APR canister reduced the overall irritant index to levels below unity, indicating that these canisters would provide protection for firefighters working in overhaul environments. However, in some tests, levels of carbon monoxide were higher than recommended for persons wearing APRs. Since these canisters do not protect against carbon monoxide, firefighters must still rely on direct reading warning to indicate high CO levels, indicating the need to leave the area if wearing an APR, as these APR canisters would be inappropriate.