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

medRxiv. 2020 Oct 6:2020.10.05.20206953. doi: 10.1101/2020.10.05.20206953. Preprint.


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 4.38×103 PFUml-1(SD 772.68) was recovered from untreated masks while 4.44×102 PFUml-1(SD 203.67), 4.00×102 PFUml-1(SD 115.47), 1.56×102 PFUml-1(SD 76.98) and 4.44×101 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.

PMID:33052360 | PMC:PMC7553180 | DOI:10.1101/2020.10.05.20206953