The effect of ultraviolet C radiation against different N95 respirators inoculated with SARS-CoV-2

Highlights • Ultraviolet C at a dose of 1.5 J/cm2 to both sides is effective on some models of N95 s. • Straps may require additional disinfection to decontaminate properly. • SARS-CoV-2 decontamination does not apply to all hospital respiratory pathogens. • N95 model and fit-testing following irradiation need to be considered for UVC decontamination.
Objectives There are currently no studies that have examined whether one dosage can be uniformly applied to different respirator types to effectively decontaminate SARS-CoV-2 on N95 filtering facepiece respirators (FFRs). Health care workers have been using this disinfection method during the pandemic. Our objective was to determine the effect of UVC on SARS-CoV-2 inoculated N95 respirators and whether this was respirator material/model type dependent. Methods Four different locations (facepiece and strap) on 5 different N95 FFR models (3 M 1860, 8210, 8511, 9211; Moldex 1511) were inoculated with a 10 μL drop of SARS-CoV-2 viral stock (8 × 107 TCID50/mL). The outside-facing and wearer-facing surfaces of the respirators were each irradiated with a dose of 1.5 J/cm2 UVC (254 nm). Viable SARS-CoV-2 was quantified by a median tissue culture infectious dose assay (TCID50). Results UVC delivered using a dose of 1.5 J/cm2, to each side, was an effective method of decontamination for the facepieces of 3 M 1860 and Moldex 1511, and for the straps of 3 M 8210 and the Moldex 1511. Conclusion This dose is an appropriate decontamination method to facilitate reuse of respirators for healthcare personnel when applied to certain models/materials. In addition, some straps may require additional disinfection to maximize the safety to frontline workers. Implementation of widespread UVC decontamination methods requires a careful consideration of model, material type, design, and fit-testing following irradiation.