Performance of Four Class 95 Electret Filters Against Diesel Particulate Matter

his study was done to assess performance of four Class 95 respirator filters exposed to diesel engine exhaust. NIOSH-certified electret filters from two manufacturers were used. N95 filters from each manufacturer were tested. P95 and R95 filters from Manufacturer X and Y, respectively, were also tested. Only R and P series filters are typically recommended for diesel exposures. Prior to diesel exposure, laboratory penetration and pressure drop were measured using applicable NIOSH certification conditions, except there was no loading test. The filters were then exposed to diesel engine exhaust from a portable air compressor. Each type of filter was divided into three groups for different exposure patterns: 1) a single exposure of 1-2 hours; 2) a single exposure of approximately 8 hours; or 3) two exposures on different days totaling approximately 8 hours. After the diesel exhaust exposure, laboratory penetration and pressure drop were retested using NIOSH test conditions. Mean laboratory penetration of Manufacturer X N95 filters increased to a high of 0.79% for the 8-hour exposure. N95 filters from Manufacturer Y showed larger increases in mean laboratory penetration, reaching 19.7% for the intermittent exposure. P95 filters remained far below 1% laboratory penetration for all exposures. Mean laboratory penetration for R95 filters increased with all exposures, up to 11% for the 8-hour exposure. Penetration of the particulate portion of the diesel exhaust was measured as elemental carbon (EC) for each group of filters using NIOSH method 5040. P95 filters did not permit detectable EC penetration. The highest mean EC penetration for any group was 4.31% for Manufacturer Y N95 filters exposed intermittently. Because of design differences among N95 filters, they should not be used for diesel particulate exposures. The R and P95 filters tested in this study would provide acceptable filtration for workplaces, where exposure conditions are less harsh than these experimental conditions.