Autoclave Sterilization and Ethanol Treatment of Re-used Surgical Masks and N95 Respirators during COVID-19: Impact on their Performance and Integrity

Grinshpun, Sergey A.; Yermakov, Michael; Khodoun, Marat

BACKGROUND: An exceptionally high demand for surgical masks and N95 filtering facepiece respirators (FFRs) during the COVID-19 pandemic has considerably exceeded their supply. These disposable devices are generally not approved for routine decontamination and re-use as standard of care while this practice has widely occurred in hospitals. The US Centers for Disease Control and Prevention allowed it “as a crisis capacity strategy.” However, limited testing was conducted on the impact of specific decontamination methods on the performance of N95 FFRs and no data was presented for surgical masks. AIM: We evaluated common surgical masks and N95 respirators with respect to the changes in their performance and integrity resulting from autoclave sterilization and a 70% ethanol treatment; these methods are frequently utilized for re-used filtering facepieces in hospitals. METHODS: The filter collection efficiency and pressure drop were determined for unused masks and N95 FFRs, and for those subjected to the treatments in a variety of ways. The collection efficiency was measured for particles of approximately 0.037–3.2 μm to represent aerosolized single viruses, their agglomerates, bacteria and larger particles carriers. FINDINGS: The initial collection efficiency and the filter breathability may be compromised by sterilization in an autoclave and ethanol treatment. The effect depends on a protective device, particle size, breathing flow rate, type of treatment and other factors. Additionally, physical damages were observed in N95 respirators after autoclaving. CONCLUSION: Strategies advocating decontamination and re-use of filtering facepieces in hospitals should be re-assessed considering the data obtained in this study.