No abstract

No abstract

2016-12-24T18:13:07

Although respirators and filters are designed to prevent the spread of pathogenic aerosols, a stockpile shortage is anticipated during the next flu pandemic. Contact transfer and reaerosolization of collected microbes from used respirators are also a concern. An option to address these potential problems is UV irradiation, which inactivates microbes by dimerizing thymine/uracil in nucleic acids. The objective of this study was to determine the effects of transmission mode and environmental conditions on decontamination efficiency by UV. In this study, filters were contaminated by different transmission pathways (droplet and aerosol) using three spraying media (deionized water . UV irradiation at constant intensity was applied for two time intervals at each relative humidity condition. The highest inactivation efficiency (IE), around 5.8 logs, was seen for DI aerosols containing MS2 on filters at LRH after applying a UV intensity of 1.0 mW/cm 2 for 30 min. The IE of droplets containing MS2 was lower than that of aerosols containing MS2. Absorption of UV by high water content and shielding of viruses near the center of the aggregate are considered responsible for this trend. Across the different media, IEs in AS and in BE were much lower than in DI for both aerosol and droplet transmission, indicating that solids present in AS and BE exhibited a protective effect. For particles sprayed in a protective medium, RH is not a significant parameter.

Inactivation of collected viral aerosols is important for preventing a filter medium's serving as a fomite. The focus of this study was to evaluate the inactivation efficiency (IE) achieved through filtration coupled with microwave irradiation. MS2 aerosolized through a Collison nebulizer was fed into the system and collected onto the filter. For in-flight microwave decontamination, microwave irradiation was applied to an HVAC (heating, ventilation and air conditioning) filter supported on a SiC disk for three cycles of selected irradiation times per 10 min (i.e., 1, 2.5, 5, and 10 min/10 min) at power levels ranging from 125 W to 375 W. The survival fraction (SF) on the substrate and the IE through the entire system were investigated to determine the efficacy of this approach. SF decreased and IE increased as microwave power level was increased (p = 0.02 and p < 0.01, respectively) or the application time was extended (p = 0.03 and p < 0.01, respectively). Both measures changed sharply above a threshold temperature of around 90°C and reached 2 logs at 116 and 109°C, respectively. The log SF and IE of -2.59 and 3.62, respectively, were observed when the operating condition of 375 W for 10 min/cycle was used and the SiC disk facilitated microwave absorption. When a quartz frit was used as a support instead of the SiC disk, log inactivation efficiencies of 0.8, 1.0, and 1.3 were measured at relative humidities of 30%, 60% and 90%, respectively, under the same irradiation conditions. Relative humidity is a significant parameter from 50-80°C (p = 0.01). The results demonstrate that microwave-assisted filtration systems can be used as an effective means for inactivating viruses.