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Study: Sterilize N95 Masks With a Microwave

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July 9, 2020 -- As one of the best lines of defense against coronavirus, N95 masks are vital for health care workers treating infected patients.

Though the masks are supposed to be used one time, the rising need and ongoing shortages have led hospitals to try mask sterilization techniques such as hydrogen peroxide vaporization, UV light, and heat incubation. A recent study from the American Society for Microbiology offers a new decontamination tool that is much more accessible and affordable: a microwave.

Researcher James E. Kirby, MD, from the Beth Israel Deaconess Medical Center of Harvard says the study’s findings are crucial to the many health care centers that lack the high-capacity sterilization systems of large hospitals.

“We knew there was a critical shortage of personal protective gear and N95 masks, and we knew there was a need for a solution,” he says.

The team of eight researchers set out to provide an easy disinfection method to different health care settings including “outpatient practices, frontline providers, and remote clinical settings.”

“The goal of this work was to identify a widely accessible, microwave-generated steam decontamination method,” the article says. “To this effect, we utilized only common household items.”

The materials include water, a glass container, mesh, a rubber band, and a 1,100- or 1,150-watt microwave. The researchers filled the container with 60 milliliters of water, then secured the mesh material over the top of it with a rubber band. They then placed the N95 mask on the mesh and microwaved it for 3 minutes. This effectively killed all viruses, including coronavirus, they say.

“It’s simple, but sometimes very simple things work well,” Kirby says.

The researchers found that this sterilization method could be repeated 20 times on a single N95 mask without damage. Even though the type of mask they used had a metal piece, they didn’t have an issue with it heating or sparking during the 20 cycles of testing, Kirby said.

Though the study was done with health care settings in mind, Kirby doesn’t see the harm in trying the same method at home.

A recent USA Today opinion piece by ICU specialists Pierre Kory, MD, and Paul H. Mayo, MD, reinforces the importance of N95s as coronavirus rates increase. Their stance is grounded on emerging evidence showing that coronavirus may be transmitted via aerosol droplets.

“The only mask that can prevent aerosol-size droplet inhalation is an N95,” the authors say.

Due to the shortage of N95s available to health care workers, many people are wearing cloth masks, which can be decontaminated in the washer. But more people may turn to N95 masks as more research emerges about the pandemic’s transmission.

Editor's note: This story was updated July 10, 2020 to add that the researchers did not see any sparking of the metal piece in the mask during the experiments. 

WebMD Health News Reviewed by Michael W. Smith, MD on July 09, 2020

Sources

American Society for Microbiology: “Microwave-Generated Steam Decontamination of N95 Respirators Utilizing Universally Accessible Materials.”

James E. Kirby, MD, Beth Israel Deaconess Medical Center. 

USA Today: “ICU doctors: Many more Americans need to wear N95 masks to slow COVID-19.”

American Medical Association.

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