The Effect of Ultraviolet C Radiation Against Different N95 Respirators Inoculated with SARS-CoV-2

Ozog, David M.; Sexton, Jonathan Z.; Narla, Shanthi; Pretto-Kernahan, Carla D.; Mirabelli, Carmen; Lim, Henry W.; Hamzavi, Iltefat H.; Tibbetts, Robert J.; Mi, Qing-Sheng

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.