Effectiveness of Ultraviolet-C Light and a High-Level Disinfection Cabinet for Decontamination of N95 Respirators

TLDR

Shortages of N95 respirators amid the COVID‑19 pandemic have created an urgent need for effective decontamination strategies. The study aims to evaluate the efficacy of various decontamination technologies for N95 respirators. The authors used a modified ASTM E‑2197‑11 quantitative carrier disk test to assess UV‑C light, a high‑level disinfection cabinet generating aerosolized peracetic acid and hydrogen peroxide, and dry heat at 70 °C for 30 min on bacteriophages Phi6, MS2, and MRSA inoculated onto three commercial N95 respirators, with 3‑ and 6‑log10 reductions defined as effective decontamination and disinfection, respectively. UV‑C light reduced contamination but failed to achieve full decontamination of viruses on N95 respirators, whereas the high‑level disinfection cabinet achieved complete decontamination of all tested organisms with three cycles, while dry heat was ineffective for bacteriophages.

Abstract

Background-Shortages of personal protective equipment (PPE) including N95 filtering facepiece respirators is an urgent concern in the setting of the global COVID-19 pandemic. Decontamination of PPE could be useful to maintain adequate supplies, but there is uncertainty regarding the efficacy of decontamination technologies.Methods-A modification of the American Society for Testing and Materials standard quantitative carrier disk test method (ASTM E-2197-11) was used to examine the effectiveness of ultraviolet-C (UV-C) light, a high-level disinfection cabinet that generates aerosolized peracetic acid and hydrogen peroxide, and dry heat at 70°C for 30 minutes for decontamination of bacteriophages Phi6 and MS2 and methicillin-resistant Staphylococcus aureus (MRSA) inoculated onto 3 commercial N95 respirators. Three and 6 log10 reductions on N95 respirators were considered effective for decontamination and disinfection, respectively. Results-UV-C administered as a 1-minute cycle in a UV-C box or a 30-minute cycle by a room decontamination device reduced contamination but did not meet criteria for decontamination of the viruses from all sites for any of the N95s. The high-level disinfection cabinet was effective for decontamination of all the organisms from the N95s and achieved disinfection with 3 disinfection cycles over ~60 minutes. Dry heat at 70°C for 30 minutes was not effective for decontamination of the bacteriophages. Conclusions-UV-C could be useful to reduce contamination on N95 respirators. However, the UV-C technologies studied did not meet our criteria for decontamination under the test conditions used. The high-level disinfection cabinet was effective for decontamination of N95s and met criteria for disinfection with multiple cycles.