Scalable, effective, and rapid decontamination of SARS-CoV-2 contaminated N95 respirators using germicidal ultra-violet C (UVC) irradiation device

Rathnasinghe, R.; Karlicek, R. F.; Schotsaert, M.; Koffas, M. A.; Arduini, B.; Jangra, S.; Wang, B.; Davis, J. L.; Alnaggar, M.; Costa, A.; Vincent, R.; Garcia-Sastre, A.; Vashishth, D.; Balchandani, P.

Importance: Particulate respirators such as N95 masks are an essential component of personal protective equipment (PPE) for front-line workers. This study describes a rapid and effective UVC irradiation system that would facilitate the safe re-use of N95 respirators and provides supporting information for deploying UVC for decontamination of SARS-CoV-2 during the COVID19 pandemic. Objective: To assess the inactivation potential of the proposed UVC germicidal device as a function of time by using 3M 8211 - N95 particulate respirators inoculated with SARS-CoV-2. Design: A germicidal UVC device to deliver tailored UVC dose was developed and snippets (2.5cm2) of the 3M-N95 respirator were inoculated with 106 plaque-forming units (PFU) of SARS-CoV-2 and were UV irradiated. Different exposure times were tested (0-164 seconds) by fixing the distance between the lamp (10 cm) and the mask while providing an exposure of at least 5.43 mWcm-2. Setting: The current work is broadly applicable for healthcare-settings, particularly during a pandemic such as COVID-19. Participants: Not applicable. Main Outcome(s) and Measure(s): Primary measure of outcome was titration of infectious virus recovered from virus-inoculated respirator pieces after UVC exposure. Other measures included the method validation of the irradiation protocol, using lentiviruses (biosafety level-2 agent) and establishment of the germicidal UVC exposure protocol. Results: An average of 4.38x103 PFUml-1(SD 772.68) was recovered from untreated masks while 4.44x102 PFUml-1(SD 203.67), 4.00x102 PFUml-1(SD 115.47), 1.56x102 PFUml-1(SD 76.98) and 4.44x101 PFUml-1(SD 76.98) was recovered in exposures 2s,6s,18s and 54 seconds per side respectively. The germicidal device output and positioning was monitored and a minimum output of 5.43 mWcm-2 was maintained. Infectious SARS-CoV-2 was not detected by plaque assays (minimal level of detection is 67 PFUml-1) on N95 respirator snippets when irradiated for 120s per side or longer suggesting 3.5 log reduction in 240 seconds of irradiation. Conclusions and Relevance: A scalable germicidal UVC device to deliver tailored UVC dose for rapid decontamination of SARS-CoV-2 was developed. UVC germicidal irradiation of N95 snippets inoculated with SARS-CoV-2 for 120s per side resulted in 100% (3.5 log in total) reduction of virus. These data support the reuse of N95 particle-filtrate apparatus upon irradiation with UVC and supports use of UVC-based decontamination of SARS-CoV-2 virus during the COVID19 pandemic.