Aerosolized Bitrex is a qualitative fit-testing agent used to screen out respirators having poor facepiece fits and thereby aids the selection of respirators with adequate facepiece fits. In this study, a total penetration test was used as an indicator of whether a respirator provided an adequate facepiece fit to its wearer using the PortaCount. Total penetration is faceseal leakage and filter penetration. Adequate protection was defined as a total penetration less or equal to 10 percent (a fit factor of less or equal to 10). This is the level of protection expected for a half-mask respirator. A panel of 25 subjects with varying facial sizes wore five different models of N95 filtering-facepiece respirators; this resulted in 125 tests. The results of the Bitrex fit texts were compared to total penetration values. The order in which testing was performed was randomized. The subject redonned the respirator between the Bitrex fit text and the total penetration test. In 59% of the tests, passing a Bitrex text correctly identified respirators having an adequate fit. In 9% of the cases, wearers passed the Bitrex test but received inadequate protection. In 41% of the texts, Bitrex results caused respirators providing adequate protection to be rejected. In 91% of the tests, failing a Bitrex test correctly identified respirators which did not provide adequate protection. These results suggest passing a Bitrex may not ensure an adequately fitting respirator.
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