Characterization of a novel, low-cost, scalable ozone gas system for sterilization of N95 respirators and other COVID-19 related use cases.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), an elusive and highly pathogenic agent, has resulted in the ongoing COVID-19 pandemic affecting numerous populations worldwide. New studies investigating the tenacity of SARS-CoV-2 have highlighted its ability to persist on a myriad of surfaces for several days, including gowns and shoes. As a result, there is a global need for sterilization of a variety of potentially-contaminated items, ranging from clothing to personal protective equipment like face coverings. To this end, we have designed and constructed a cost-effective, scalable, and sustainable sterilization system that uses ozone gas to inactivate viral particles. We sought to determine the efficacy of the system in the sterilization of viral particles as well as its ability to sterilize N95 respirators for reuse. N95 respirators inoculated with P22 bacteriophage and sterilized in the ozone system showed a 6-log10 reduction in viral load when treated at 25 ppm for 150 minutes. Further, N95 respirators treated with five 150-minute cycles at 35 ppm for a total concentration-time product (CT) of 26,250 ppm min in the ozone system showed comparable filtration efficiency to untreated N95 respirators in a 50 to 200 nmr particulate challenge filtration test. Interestingly, the surgical N95 respirators tested showed complete inactivation of fluid resistance and degradation of the elasticity of polyisoprene straps after five cycles in the sterilization system. Taken together, these data suggest that while our ozone system may negatively affect certain protective aspects of surgical N95 respirators, it does effectively sterilize viral particles and can be utilized for a multitude of other use cases, including sterilizing polypropylene face coverings after potential SARS-CoV-2 contamination. In addition to providing long-term environmental benefits, deployment of this system during the ongoing pandemic reduces the risk of COVID-19 community transmission while conserving monetary resources otherwise spent on the continuous purchase of disposable face coverings.