Vapor H2O2 sterilization as a decontamination method for the reuse of N95 respirators in the COVID-19 emergency

Ebru Oral; Keith K Wannomae; Rachel L Connolly; Joseph A Gardecki; Hui Min Leung; Orhun K Muratoglu; Anthony Griffiths; Anna N Honko; Laura E Avena; Lindsay GA McKay; Nick Flynn; Nadia Storm; Sierra N Downs; Ralph Jones; Brandon Emmal

The VHP treatment was performed using a Steris ARD1000® in a 691 ft 3 room; samples were exposed to 410± 83 ppm of vaporized hydrogen peroxide for approximately 3 hours followed by off-gassing until hydrogen peroxide was undetectable (0 ppm, approximately 4.5 hours total from initiation of VHP cycle). Following VHP exposure, respirator pieces were added to 2mL of DMEM + 2% FBS + antibiotics/antimycotics (Gibco™) and vortexed at 2,000 rpm for 2 minutes, followed by centrifugation at 1,000 RCF for 5 minutes. Virus from plastic dishes was resuspended in 2mL of complete DMEM. Infectivity was quantified using a plaque assay in duplicate using 200 µL of the undiluted eluate to a 1:10,000 dilution. Additionally, samples were plated (500µL) in duplicate on cells and following a 1-hour incubation, 1.5mL complete DMEM was added. These plates were observed for cytopathic effect for five days.