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| Credit NIOSH |
#15,308
For well over a decade we've been discussing the inevitable shortage of N95 respirators (and surgical masks) during a pandemic (see 2009's Caught With Our Masks Down). Although our National Strategic Stockpile contained over 100 million respirators, that was less than 2% of what was estimated as being needed for a severe pandemic.
Since the math was obvious - and no one seemed willing to stockpile the quantity of PPEs required - we saw a push for alternative plans (see 2014's NIOSH: Options To Maximize The Supply of Respirators During A Pandemic).Basic PPEs should have been the foundation of our public health pandemic response, not an afterthought. But we have what we have, and so HCWs and hospitals across the country and around the world have had to find creative ways to stretch supplies as best they can.
One idea, heavily promoted by the White House, has been the decontamination and reuse of N95 respirators - which are normally a one-time-use item - suggesting that respirators might be reused up to 20 times.
Last March, in ECDC Technical Document: Cloth Masks & Mask Sterilization Options, we looked at several potential processes, including steam, Hydrogen Peroxide Vapor, and Gamma Radiation - all of which present significant challenges (mask deformation, and even toxic chemical residues).Today we have a new research letter - published in the EID Journal - that looks at four decontamination processes (Ethanol, Dry Heat, Vaporized Hydrogen peroxide (VHP), & UV light), and finds that N95 respirators can be decontaminated and reused, but that the fit and filtration can degrade over several cycles.
I've only posted some excerpts, so follow the link to view the entire article and accompanying graphics.
Research Letter
Effectiveness of N95 Respirator Decontamination and Reuse against SARS-CoV-2 Virus
Robert J. Fischer, Dylan H. Morris, Neeltje van Doremalen, Shanda Sarchette, M. Jeremiah Matson, Trenton Bushmaker, Claude Kwe Yinda, Stephanie N. Seifert, Amandine Gamble, Brandi N. Williamson, Seth D. Judson, Emmie de Wit, James O. Lloyd-Smith, and Vincent J. Munster
Abstract
The coronavirus pandemic has created worldwide shortages of N95 respirators. We analyzed 4 decontamination methods for effectiveness in deactivating severe acute respiratory syndrome coronavirus 2 virus and effect on respirator function. Our results indicate that N95 respirators can be decontaminated and reused, but the integrity of respirator fit and seal must be maintained.
The unprecedented pandemic of coronavirus disease has created worldwide shortages of personal protective equipment, in particular respiratory protection such as N95 respirators (1). Transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) occurs frequently in hospital settings; numerous reported cases of nosocomial transmission highlight the vulnerability of healthcare workers (2). The environmental stability of SARS-CoV-2 virus underscores the need for rapid and effective decontamination methods.
In general, N95 respirators are designed for one use before disposal. Extensive literature is available for decontamination procedures for N95 respirators, using either bacterial spores, bacteria, or respiratory viruses (e.g. influenza A virus) (3–6). Effective inactivation methods for these pathogens and surrogates include UV light, ethylene oxide, vaporized hydrogen peroxide (VHP), gamma irradiation, ozone, and dry heat (A. Cramer et al., unpub data, (3–6).
The filtration efficiency and fit of N95 respirators has been less well explored, but reports suggest that both filtration efficiency and N95 respirator fit can be affected by the decontamination method used (7; Appendix).
(SNIP)
Our findings showed that VHP treatment had the best combination of rapid inactivation of SARS-CoV-2 virus and preservation of N95 respirator integrity under the experimental conditions (Figure, panel C). UV light killed the virus more slowly and preserved respirator function almost as well. Dry heat at 70ºC killed the virus with similar speed to UV and is likely to maintain acceptable fit scores for 1–2 rounds of decontamination but should not be used for 3 rounds. Consistent with earlier findings (8), ethanol decontamination reduced N95 integrity and is not recommended.
All treatments, particularly UV light and dry heat, should be conducted for long enough to ensure sufficient reduction in virus concentration. The degree of required reduction depends upon the degree of initial virus contamination. Policymakers can use our estimated decay rates together with estimates of real-world contamination to choose appropriate treatment durations (Appendix).
Our results indicate that, in times of shortage, N95 respirators can be decontaminated and reused up to 3 times by using UV light and HPV and 1–2 times by using dry heat. Following nationally established guidelines for fit testing, seal check, and respirator reuse is critical (9,10). We recommend performing decontamination for sufficient time and ensuring proper function of the respirators after decontamination using readily available qualitative fit testing tools.
Dr. Fischer is a member of the Virus Ecology Section at the Rocky Mountain Laboratories. His research interests include the ecology of emerging viruses in their natural and spillover hosts, including SARS-CoV-2.
According to Kaiser Health News, the HPV (Battelle) process takes about 12 hours, and since masks must be collected and shipped to a processing center, the turn around time can be up to 10 days.
A report from WOSU Public Media - posted June 1st - indicates that most of the masks returned have been functional, but a few problems and/or concerns have been reported.
U.S. Hospitals Greet Battelle's PPE Cleaning Units With Gratitude, And Some Concern
Today's research letter, however, suggests that N95's should be decontaminated only 3 times using this method, which is in sharp contrast to the 20 times being promoted by Battelle. As to which is closest to reality, your guess is as good as mine.
Hopefully we'll get more data as the summer progresses, and have a better idea on the practical (and logistical) limits of decontaminating N95s before fall.
Stay tuned.
