The only 30 CFR 11 filters which could be used in quantitative fit testing were high-efficiency particulate aerosol (HEPA) filters. These were the only filters which did not have significant penetration of the aerosols used in quantitative fit tests. However, the new National Institute for Occupational Safety and Health (NIOSH) respirator certification regulations (42 CFR Part 84) require all particulate respirators to be tested with an aerosol in the most penetrating size range and to have a minimum filter efficiency of 95%. As a result of improved filter performance assured by these new regulations, a question has arisen regarding whether N95 respirators (one of the new classes of particulate respirators) could be quantitatively tested. In response, NIOSH and TSI Incorporated researchers developed a method for testing N95 filtering-facepiece respirators using the PortaCount Plus with a filter ratio test clamp to measure filter penetration. Meanwhile, TSI also developed a new accessory (the N95-COMPANION for the PortaCount Plus) to fit test N95 respirators. The purpose of the study was to determine how well the fit factors from these two methods correlate. The facepiece fit of each respirator model was measured on a panel of 25 subjects with varying face sizes. A "standard" PortaCount Plus test was conducted for each subject/respirator combination. However, since N95 filter media can have significant penetration of ambient particles, the "standard" PortaCount Plus fit test measured total penetration (i.e.,filter penetration and face seal leakage) and not just face seal leakage. Filter penetration was measured on each respirator using the PortaCount Plus with the clamp, and an adjusted fit factor computed. Immediately after the "standard" PortaCount Plus test, a fit test for each subject/respirator combination was conducted using the N95-COMPANION without the respirator being redonned. Log-transformed Companion fit factors and log-transformed adjusted fit factors were strongly correlated (R2 ranged from 0.66 to .92 depending on the regression models). The slope of the regression equation for one respirator model was significantly different from the slopes for the other four respirator models. The authors concluded that both methods provided comparable fit factors for each respirator/subject combination. Future studies should characterize the ambient particle size distribution inside the N95 filtering-facepiece respirators
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