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

Since March 31 ^st , 2020, during the height of the pandemic, we have decontaminated thousands of 3M 1860 respirators with Ultraviolet C (UVC) for our frontline workers. There is no published peer-reviewed data regarding the dose required to effectively disinfect SARS-CoV-2 on N95 filtering facepiece respirators (FFRs). Four different locations (facepiece and strap) on 5 different N95 FFR models (3M 1860, 8210, 8511, 9211; Moldex 1511) were inoculated with a 10 μL drop of SARS-CoV-2 viral stock (8 × 10 ⁷ TCID ₅₀ /mL). The outside-facing and wearer-facing surfaces of the respirators were each irradiated with a dose of 1.5 J/cm ² UVC (254 nm).

Viable SARS-CoV-2 was quantified by a median tissue culture infectious dose assay (TCID ₅₀ ). UVC delivered using a dose of 1.5 J/cm ² , to each side, was an effective method of decontamination for the facepieces of 3M 1860 and Moldex 1511, and for the straps of 3M 8210 and the Moldex 1511. This dose is an appropriate decontamination method to facilitate reuse of respirators for healthcare personnel when applied to certain models/materials. Increasing the dose may improve decontamination for the other models and straps; however, UVC radiation can degrade certain polymers in a dose dependent manner, and the effects may vary greatly between different models. Therefore, fit-testing of UVC decontaminated respirators must be performed each time a new model and/or dose is introduced into the healthcare system.