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

Prior to the pandemic we routinely monitored air quality in a magnetically-shielded, biomagnetic clean lab 8 in the 0.3, 0.5, 1 and 10 μm size bins using a MetOne TM Aerocet 531S laser particle counter, which is NIST-referenced and meets or exceeds CE and ISO 21501 certifications. These units sample air at ambient pressure with a small pump, running it through the laser detectors and counting particles in the four size bins. In order to use this to sample the air passing through a filter, we constructed a testing facility as shown in Fig. 1 . We wrapped a Styrofoam bust of a human head (previously used as an EEG blank) in three layers of ordinary kitchen plastic wrap to give surface friction and pliancy, drilled a vent hole "mouth", and placed the N95 respirators over the opening. This setup was housed inside a Plexiglass box, which was then pressurized with 'dirty' Pasadena air (the pressurized box reached ~2,000,000 particles > 0.3 μm/cf) using an industrial heat gun dryer (a Gilson TM MA-290F) in non-heat mode, mounted to the side. Air passed through the filters and then exited through a PVC pipe, which was sampled by the particle counter at ambient pressure. The air then flowed through a 2 m length of plastic hose to minimize backflow of outside air into the counter from turbulence. The flow rate through the mask was adjusted using the intake manifold on the heat gun to ~23 l/min.