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

Performance degradation in N95 face respirators is likely caused partially by moisture on the polypropylene fibers. We identify an effective disinfection and restoration method: rinsing the face masks in a 70% v/v ethanol solution, then air drying, followed by pumping on them in a vacuum chamber to a pressure below 6 mBar. We replicated previous reports that alcohol-based decontamination could result in a decrease in efficiency of ~40% after air-drying. As of this writing, we have conducted 18 wet/dry/vacuum cycles on 6 different masks, all of which drop in performance after wetting, but return to within 98% of their initial filtration efficiency after vacuum treatment to < 6 mBar. In addition, this restoration has been verified for up to 5 cleaning cycles on the N95 rated 3M TM 8200, 8210 and 8511 masks.