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

Abstract

Background: Shortages of personal protective equipment (PPE) including N95 respirators are 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.Correction: This is a corrected version of this article. The original version of this article contained data for an additional ultraviolet light device that has been removed from the corrected version as the device tested is no longer manufactured or supported by the manufacturer. The authors have offered to collaborate with the manufacturer to complete additional testing with a current version of the technology. 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 3 methods, including 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. We assessed the decontamination of 3 commercial N95 respirators inoculated with methicillin-resistant Staphylococcus aureus (MRSA) and bacteriophages MS2 and Phi6; the latter is an enveloped RNA virus used as a surrogate for coronaviruses. Three and 6 log 10 reductions on 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 on the N95s. The high-level disinfection cabinet was effective for decontamination of the N95s and achieved disinfection with an extended 31-minute cycle. 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 pre-established criteria for decontamination under the test conditions used. The high-level disinfection cabinet was more effective and met criteria for disinfection with an extended cycle.

Scalable in-hospital decontamination of N95 filtering face-piece respirator with a peracetic acid room disinfection system

“…25,36 However, an extended cycle with the disinfection cabinet was required to achieve a 6 log 10 reduction in bacteriophage MS2 inoculated on N95 respirators. 18 In the current study, an extended cycle (identified as the optimal disinfection cycle in our experiments) was also required to achieve a 6 log 10 reduction in bacteriophage MS2 or G. stearothermophilus spores on N95 respirators. Similarly, Battelle has reported a prolonged VHP cycle time with a total time of 480 minutes for N95 decontamination.…”

“…The test and control respirators were inoculated with ~10 6 colony-forming units (CFU) of G. stearothermophilus spores and ~10 6 plaque-forming units (PFU) of bacteriophage MS2 on the outer and inner surface of the respirator as previously described. 18,25,26 The test organisms were suspended in 8% simulated mucus, 27 and 10 µL aliquots were pipetted onto the respirator surface and spread with a sterile loop to cover an area of 1 cm 2 and allowed to air dry. The test N95 respirators were suspended using metallic 'S' shaped hooks from shelving carts at a height of feet and exposed to PAA submicron droplets.…”

Lower Incidence of COVID-19 at High Altitude: Facts and Confounders

“…Another benefit of greater UV radiation at high altitude will be possibly higher vitamin D levels, which afford protection against several other viral and bacterial infections by T cell enhancement (Grant et al, 2020). Thus, UV radiation might, theoretically, contribute to slowing the spread of the virus as some groups have suggested (Cadnum et al, 2020;Hamzavi et al, 2020;Keil et al, 2020), but this needs to be examined carefully. However, any action of UV radiation will only be relevant to the outdoor environment and most viral transmission occurs indoors, where people congregate in closer quarters and spend many hours of the day.…”

Rapid Review of SARS-CoV-1 and SARS-CoV-2 Viability, Susceptibility to Treatment, and the Disinfection and Reuse of PPE, Particularly Filtering Facepiece Respirators

“…While different regimens of UVGI and heat treatment are effective against a large number of human pathogens, there is a high degree of variability among the susceptibility to temperature and UVC among microorganisms [ 59 , 120 ]. Thus, while the disinfection procedures reviewed here have focused on SARS-CoV-1 and SARS-CoV-2, they would not necessarily be efficacious against all other pathogens, in particular spore-forming bacteria.…”