Differentiating Between Physical and Viable Penetrations When Challenging Respirator Filters with Bioaerosols

Abstract

The feasibility of a novel testing protocol that allows differentiating between the physical (total) and viable bioaerosol penetrations through respirator filters was investigated. Three respirator models -two conventional N95 filtering-facepiece respirators (FFR) used as controls and one P95 iodinated polymer FFR with antimicrobial properties -were challenged with aerosolized MS2 bacteriophage virus. Physical (P physical ) and viable (P viable ) filter penetrations were simultaneously measured with the FFR sealed on a manikin at a constant inhalation flow rate of 85 L/min. Separate testing was performed on specially-manufactured P95 filter swatches with (i) no iodinated resin additive and (ii) "high" amount of the additive to determine whether it influenced filtration behavior of the P95 respirator. Bioaerosol collection on the N95 FFR filters fell in the range consistent with previous studies featuring about 2% penetration for MS2 and a peak around l5%. The P95 iodinated polymer respirator was found to be highly efficient, attributed in part to the iodinated resin powder which in separate swatch tests was found to increase the filter collection efficiency. No statistically significant differences were observed between penetration values obtained for total and culturable viruses for the two control respirators. Similarly, no difference was observed for the iodinated respirator, which suggested that the microbial inactivation effect was of insufficient magnitude to be detected or was not present for viral particles that penetrated the filter. Possible "long-term" inactivation effect of the iodine-based additive on the viable viruses, which were captured on the filter over time, was beyond the scope of this study. The novel testing protocol appears to be an adequate tool for evaluating respirators designed to protect against bioaerosol particles. Further improvement may be considered with respect to the aerosolization method for viable microorganisms.

Performance of Conventional and Antimicrobial-Treated Filtering Facepiece Respirators Challenged with Biological Aerosols

“…Thus, in contrast to Lee et al, (26) no statistical differences in PEN V were observed for the AM-FFR tested with or without the iodine neutralizer in our study. This may be due to several experimental differences resulting in less iodine vapor accumulation in the AGI sampling fluid in this study than in that of Lee et al In this study the airflow rate was a factor of two lower (face velocity of 7 cm/s vs. 14.2 cm/s), the sampling time was a factor of six shorter (20 min vs. 2 hr), and the loading of the iodine treatment was a factor of 10 lower (∼10 g/m 2 for a commercial AM-P95 FFR (27) vs. 125g/m 2 ). Because Table IV are based on combining both sets of PEN V measurements taken with and without iodine neutralizer as they were not found to be statistically different.…”

Evaluation of the Performance of Iodine-Treated Biocidal Filters Under the Influence of Environmental Parameters

“…Its capability for inactivating airborne bacteria and viruses has been reported in several studies (Foarde et al 2000;Heimbuch et al 2004;Heimbuch and Wander 2006;Ratnesar-Shumate and Wu 2004;Ratnesar-Shumate et al 2008). Other studies that also lacked appropriate controls reported no difference in the performance between conventional and iodine-treated FFRs for penetrating bioaerosols (Eninger et al 2008;Lore et al 2012). The capacity of various proteins (such as gelatin or bovine serum albumin, BSA) to take up iodine (Eninger et al 2008), the reversibility of iodine attachment ) and the use of water-based collection and analytical media, which are known to create an efficient kill mechanism (Taylor et al 1970) combine to form challenges to attaining a definitive measurement to verify the antimicrobial mechanism of PSTI as well as its practical significance.…”

Bioaerosol Science, Technology, and Engineering: Past, Present, and Future

“…For personal exposure protection, respiratory filter masks, such as N95 respirators, and surgical masks are widely adopted (Burton et al 2007;Lee et al 2008). The bioaerosol filtration efficiencies of these respirators were extensively studied, and it was shown that the N95 filtering face piece respirators may not provide the expected protection level against small virions (Balazy et al 2006a(Balazy et al , 2006bEninger et al 2008aEninger et al , 2008bShaffer and Rengasamy 2009). In a review article, it was pointed out that the respiratory protection against bioaerosol exposure is dependent on several factors: bioaerosol size and filter characteristics, flow rate, face-fitting characteristics, and efficiency degradation of filter material (Rengasamy et al 2004).…”