N95 masks unsafe to use after 2nd sterilization: Winnipeg hospital study

A worker wears a protective suit as precautionary measure while making an N95 mask at Atfil factory (High Technology in Air Filtration), Mexico City, Mexico, May 21, 2020. Photo by Carlos Tischler/Eyepix/ABACAPRESS.COM

A new study out of Winnipeg suggests that after an N95 mask is worn and sterilized more than once, it starts to fail safety tests.

Earlier this year. researchers at the St. Boniface Hospital Albrechtsen Research Centre began examining how the masks’ performance, when used by health-care workers during the coronavirus pandemic, would be affected by sterilization after eight hours of wear.

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“The results showed that yes, we can safely re-sterilize the kind of single-use N95 masks typically worn by health care workers in order to gain a second use, but not more than that,” said Dr. Mike Czubryt, principal investigator at St. Boniface Hospital Research Centre.

The study was recently accepted for publication by the Journal of Hospital Infection.

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Czubryt and his team found that after being worn in real-life conditions and sterilized once, the masks passed all material, fit and filtration tests. But a second time around yielded different results.

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“After a second sterilization cycle, the masks started to fail the fit testing, deeming them unsafe for use in a health-care setting,” Czubryt said.

The team called the results “discouraging” after previous studies showed that the masks could be chemically sterilized up to 10 times.

However, those studies didn’t take into account real-world use, said Czubryt.

“Since masks can be re-sterilized once, that will still theoretically double the current stockpile of N95s around the world.

“So this information should be helpful for health-care decision makers who are looking at exactly how far they can stretch their stockpile and how much to order from suppliers for future needs.”

The study will benefit health-care facilities with a “workflow… to safely recycle hundreds of masks per day while keeping workers safe,” Czubryt added.

“The team believes that if adopted broadly, our mask re-sterilization protocol could dramatically improve global availability, particularly in areas hardest hit by COVID-19 where supplies are low and new shipments delayed.”

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