N95 masks can be safely decontaminated and reused, study shows
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Researchers found that decontaminating N95 respirators using vaporized hydrogen peroxide provided a “viable means” to reuse the masks without compromising their effectiveness.
Christina F. Yen, MD, who was a clinical infectious diseases fellow at Beth Israel Deaconess Medical Center in Boston during the project, and colleagues conducted a prospective cohort study from June 15 through Aug. 31, 2020, to determine if reprocessed N95 masks remained effective following 25 cycles of vaporized hydrogen peroxide (VHP).
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The researchers determined the continued function of the masks by their ability to filter 95% or more of airborne particles 0.3 µm or greater in diameter. They determined masks’ effectiveness through user seal checks — participants checked the seal of their respirators by donning and doffing the masks after each VHP cycle. If reprocessed masks did not meet these requirements, they were removed from the study.
They selected three male and four female participants for the study and fitted them for 3M 1860/1860S N95 masks. No participants had any facial hair because it would have impacted the seal, the researchers said.
They tested the filtration efficacy of seven masks — one for each participant — first with narrow particles, sized 0.3 to 0.375 µm, and then larger particles sized 0.3 to 10 µm. They assessed them at baseline after cycles 10, 15, 20 and 25.
All reprocessed masks met the primary endpoints after 25 user seal checks, eight quantitative and four qualitive fit tests, and filtration efficacies remained 95% or higher, according to the researchers. Filtration efficacy was 100% for narrow particles and 99.95% for larger particles.
“The findings from our study expand upon previous findings that VHP is a relatively safe method for reprocessing N95 respirators, and could help address shortages in future epidemics,” Yen said in a news release. “It is important that we now find ways to scale and translate this capability to smaller hospitals and resource-limited health care settings that could benefit just as much — perhaps more — from this type of personal protective equipment reprocessing in future disaster scenarios.”
According to the authors, current studies that evaluate masks often perform either qualitative or quantitative tests but never both. By conducting both types of tests, the authors said they addressed the potential for subject failures.
The type of mask and VHP decontamination are common, which increases the generalization of the findings, they said.
The authors noted that similar studies that assess fit often use mannequins, whereas the authors used human participants, which allowed the design to mirror “real-life variability in facial structure and size.”
Last year, researchers reported that universal use of N95 masks by health care workers in COVID-19 hot spots could lower nosocomial transmission of SARS-CoV-2.
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