Performance of conventional and antimicrobial-treated filtering facepiece respirators challenged with biological aerosols

This study evaluated the filtration performance of four commercially available models of National Institute of Occupational Safety and Health (NIOSH)-certified filtering facepiece respirators (FFR) against both biological and inert aerosols at a flow rate of 85 L/min. Conventional N95 and P100 FFRs and two antimicrobial (AM)-treated FFRs (an N95 and a P95, both with iodine-based AM treatments) were tested for both physical penetration (PEN _P) and viable penetration (PEN _V) with three different bioaerosols, including MS2 bacteriophage virus, and the spores and vegetative cells of Bacillus atrophaeus bacteria, in addition to inert sodium chloride (NaCl) aerosol. For each FFR model, the PEN _P measured with NaCl was predictive of its MS2 PEN _P, and it was observed that spores and bacteria aerosols were also filtered similarly to the inert aerosol. For both conventional FFRs, up to a 1-log reduction in PEN _V in comparison with PEN _P was observed and attributed to the experimental variability of the test system. For both models of AM-FFRs, no statistically significant differences between PEN _V and PEN _P for any of the three different bioaerosol challenges were observed. Thus, no bioaerosol filtration enhancement over the conventional FFRs was detected for either iodine-based AM-FFR. In the absence of any standardized test methods, we recommend that future studies evaluating the filtration performance of AM-treated FFRs incorporate the experimental best practices described herein.