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.

Elastomeric, half-facepiece, air-purifying respirator performance in a lead battery plant.

This workplace protection factor (WPF) study of a half facepiece air-purifying respirator with P100 filters was done in a lead battery manufacturing plant. Paired air samples for lead were collected inside and outside respirators worn by workers who were properly trained and quantitatively fit tested. Of the 45 valid sample sets, only four had detectable lead on the inside sample. WPFs were calculated for these sample pairs by dividing the outside sample lead concentration (C(o)) by the inside concentration (C(i)). For the remaining 41 sample pairs, the detection limit for lead was used to calculate a maximum estimated C(i) concentration. The C(o) for each of these sample pairs was divided by the C(i) estimate to obtain a minimum WPF value. All the WPFs were rounded down to two significant figures, resulting in values ranging from 12 to > 2500. A rank and percentile procedure resulted in a 50th percentile WPF of 270 and a lower 5th percentile estimate > 50. These WPFs exceed the assigned protection factor of 10 for half facepieces published by the Occupational Safety and Health Administration. This study's results support the APF of 10 and indicate the respirator provided appropriate protection as it was used in this study. The comparability of the two analytical methods commonly used together in WPF studies was also evaluated. The samples collected outside the respirators were analyzed for lead by proton-induced X-ray emission analysis (PIXE) followed by inductively coupled plasma spectrometry (ICP). While the two methods were highly correlated (r(2) = 0.965), the mean PIXE lead mass was approximately 45% higher than the mean ICP value. This systematic bias was explained by the assumptions used to interpret the PIXE analytical results. When WPF studies use ICP and PIXE for C(o) and C(i) samples, respectively, the calculated WPF values are conservative estimates of respirator performance.