Background: An exceptionally high demand for surgical masks and N95 filtering facepiece respirators (FFRs) during the COVID-19 pandemic has considerably exceeded their supply. These disposable devices are generally not approved for routine decontamination and reuse as a standard of care, while this practice has widely occurred in hospitals. The US Centers for Disease Control and Prevention allowed it "as a crisis capacity strategy". However, limited testing was conducted on the impact of specific decontamination methods on the performance of N95 FFRs and no data was presented for surgical masks. Aim: We evaluated common surgical masks and N95 respirators with respect to the changes in their performance and integrity resulting from autoclave sterilization and a 70% ethanol treatment; these methods are frequently utilized for re-used filtering facepieces in hospitals. Methods: The filter collection efficiency and pressure drop were determined for unused masks and N95 FFRs, and for those subjected to the treatments in a variety of ways. The collection efficiency was measured for particles of approximately 0.037e3.2 mm to represent aerosolized single viruses, their agglomerates, bacteria and larger particle carriers. Findings: The initial collection efficiency and the filter breathability may be compromised by sterilization in an autoclave and ethanol treatment. The effect depends on a protective device, particle size, breathing flow rate, type of treatment and other factors. Additionally, physical damages were observed in N95 respirators after autoclaving. Conclusion: Strategies advocating decontamination and re-use of filtering facepieces in hospitals should be re-assessed considering the data obtained in this study.

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Outdoor traffic-related airborne particles can infiltrate a building and adversely affect the indoor air quality. Limited information is available on the effectiveness of high efficiency particulate air (HEPA) filtration of traffic-related particles. Here, we investigated the effectiveness of portable HEPA air cleaners in reducing indoor concentrations of traffic-related and other aerosols, including black carbon (BC), PM , ultraviolet absorbing particulate matter (UVPM) (a marker of tobacco smoke), and fungal spores. This intervention study consisted of a placebo-controlled cross-over design, in which a HEPA cleaner and a placebo "dummy" were placed in homes for 4-weeks each, with 48-hour air sampling conducted prior to and during the end of each treatment period. The concentrations measured for BC, PM , UVPM, and fungal spores were significantly reduced following HEPA filtration, but not following the dummy period. The indoor fraction of BC/PM was significantly reduced due to the HEPA cleaner, indicating that black carbon was particularly impacted by HEPA filtration. This study demonstrates that HEPA air purification can result in a significant reduction of traffic-related and other aerosols in diverse residential settings.

Accidental release of biological agents from a bioweapon facility may contaminate large areas, possibly causing disastrous environmental consequences. To address this issue, novel halogen-containing reactive materials are being designed with the added capability to inactivate viable airborne microorganisms. This study determined the efficiency of combustion products of such materials to inactivate aerosolized bacteria and viruses. Spores of Bacillus atrophaeus and MS2 viruses dispersed in dry air were exposed for subsecond time intervals to hydrocarbon flames seeded with different reactive powders so that bioaerosol particles interacted with the combustion products in a controlled high-temperature environment. The experiments were designed to quantify differences in the biocidal effects of different reactive material powders including Al and Mg, a B•Ti nanocomposite, an 8Al•MoO(3) nanothermite, and a novel Al•I(2) nanocomposite. Compared to pure hydrocarbon flame, powder-seeded flame (with no iodine) produced about an order of magnitude greater inactivation of bacterial spores. The iodine-containing material increased the spore inactivation by additional 2 orders of magnitude. The aerosolized MS2 viruses (generally not as stress-resistant as spores) were fully inactivated when exposed to combustion of either the iodinated or noniodinated powders. Overall, the study suggests a great biocidal potential of combustion products generated by novel iodine-containing nanocomposite materials.

SMs do not provide measurable protection against surgical smoke. SMRs offer considerably improved protection versus SMs, while the N100 FFRs showed significant improvement over the SMRs. The FS prototype offered a higher level of protection than the standard N100 FFR, due to a tighter seal. While we acknowledge that conventional N100 FFRs (equipped with exhalation valves) are not practical for human OR use, the results obtained with the FS prototype demonstrate the potential of the new FS technology for implementation on various types of respirators.