Decontamination of N95 and surgical masks using a treatment based on a continuous gas phase-Advanced Oxidation Process

Abstract

A gas-phase Advanced Oxidation Process (gAOP) was evaluated for decontaminating N95 and surgical masks. The continuous process was based on the generation of hydroxyl-radicals via the UV-C (254 nm) photo-degradation of hydrogen peroxide and ozone. The decontamination efficacy of the gAOP was dependent on the orientation of the N95 mask passing through the gAOP unit with those positioned horizontally enabling greater exposure to hydroxyl-radicals compared to when arranged vertically. The lethality of gAOP was independent of the applied hydrogen peroxide concentration (2–6% v/v) but was significantly (P<0.05) higher when H2O2 was introduced into the unit at 40 ml/min compared to 20 ml/min. A suitable treatment for N95 masks was identified as 3% v/v hydrogen peroxide delivered into the gAOP reactor at 40 ml/min with continuous introduction of ozone gas and a UV-C dose of 113 mJ/cm2 (30 s processing time). The treatment supported >6 log CFU decrease in Geobacillus stearothermophilus endospores, > 8 log reduction of human coronavirus 229E, and no detection of Escherichia coli K12 on the interior and exterior of masks. There was no negative effect on the N95 mask fitting or particulate efficacy after 20 passes through the gAOP system. No visual changes or hydrogen peroxide residues were detected (<1 ppm) in gAOP treated masks. The optimized gAOP treatment could also support >6 log CFU reduction of endospores inoculated on the interior or exterior of surgical masks. G. stearothermophilus Apex spore strips could be applied as a biological indicator to verify the performance of gAOP treatment. Also, a chemical indicator based on the oxidative polymerization of pyrrole was found suitable for reporting the generation of hydroxyl-radicals. In conclusion, gAOP is a verifiable treatment that can be applied to decontaminate N95 and surgical masks without any negative effects on functionality.

The influence of COVID-19 pandemic on biomedical waste management, the impact beyond infection

“…Recently active hydroxyl radical-based decontamination of surgical and N95 masks had been carried out through photo degeneration of hydrogen peroxide and ozone by UV-C. This process is also called “gas-phase Advanced Oxidation Process (gAOP)” (Hasani et al, 2021 ). Another study showed that moist heat and chemical treatment with salt (NaCl) and N-halamide can dramatically reduce pathogenic contaminants from used masks (Zorko et al, 2020 ).…”

TCID50 Measurements of anti-viral efficacy on metal printed masks and plastic surfaces

“…A back titer of the viral stock was performed with each experiment. The log reduction was calculated using the R-log reduction method (33)(34)(35). Ca is the TCID50 value of the infected group, and Cb is the TCID50 value of the uninfected control group.…”

Surface disinfection of wheat kernels using gas phase hydroxyl‐radical processes: Effect on germination characteristics, microbial load, and functional properties

“…The principle of the hydroxyl-radical generating process was later adapted to a gas phase treatment based on H 2 O 2 vapor coupled with ozone gas. The gas phase hydroxyl-radical process has been applied to decontaminate the surface of food and nonfoods within a continuous, low moisture process (Hasani et al, 2019(Hasani et al, , 2021. H 2 O 2 and/or ozone can be degraded by UV-C light and generate free radicals (hydroxyl-radicals) (Krishnan et al, 2017).…”