An Efficient Ethanol-Vacuum Method for the Decontamination and Restoration of Polypropylene Microfiber Medical Masks & Respirators

Albert I. Nazeeri; Isaac A. Hilburn; Daw-An Wu; Kabir A. Mohammed; D. Yovan Badal; Moses H.W. Chan; Joseph L. Kirschvink

is the (which was not peer-reviewed) The copyright holder for this preprint . https://doi.org/10.1101/2020.04.12.20059709 doi: medRxiv preprint Results: Table 1 lists the medical masks and respirators that we have examined so far. New N95 respirators from 3M TM typically gave filtration readings above 95% (consistent with their N95 rating from NIOSH), and other mask types with lower ratings gave similarly consistent results. Although we did not use standard ASHRAE aerosol procedures, data from the experimental setup, shown in Fig. 1 , are in agreement with those procedures and verify the utility of our experimental setup. Similarly, the N95 respirators dropped in efficiency by 20-30% following alcohol cleaning; this is consistent with previously reported results 3, 4 . Table 2 shows the results from five cycles of alcohol decontamination / drying that were conducted on three varieties of 3M TM N95 respirators (3M TM 8200, 8210 and 8511 masks). After these cycles, all masks remained at or above 95% filtration efficiency. As of this writing have conducted 18 wet/dry/vacuum cycles on 6 different masks, all of which drop in performance after wetting, but return to within 99% of their initial filtration efficiency after vacuum treatment to < 6 mBar.