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Hospitals are scrambling to sterilize and reuse N95 masks, deploying high-tech methods like ultraviolet light and concentrated hydrogen peroxide. But the father of the modern N95 mask thinks a much simpler technique could work: heating them.
Peter Tsai is a material scientist credited with inventing technology that makes material used in N95 masks. He told VICE News that he’s researching whether blasting the masks at intense temperatures for short periods would kill the virus without degrading the mask. He hopes to publish the results of his research within days.
“We are going to use heat, [158 degrees Fahrenheit (70 degrees Celsius)], for 30 minutes, to see if we can kill COVID-19,” he said on Tuesday afternoon. “We should get the results in one or two days.”
Tsai, a recently retired professor at the University of Tennessee, is one of several researchers at companies or institutions looking at heat as a potential low-tech solution for the shortage of masks plaguing hospitals around the country. Desperate to stretch their personal protective equipment for much longer than its intended single use, nurses and doctors told VICE News they’re using alcohol or even Clorox wipes to try to decontaminate their masks — a desperate move that could do more harm than good.
“Obviously no one wants to spray down their N95s every day and reuse PPE [personal protective equipment], but until we receive government support and safety of healthcare workers becomes a priority, we have no choice,” said a resident at Elmhurst Hospital in Queens. “The hospitals simply don’t have the supplies.”
“We should get the results in one or two days.”
Before the coronavirus pandemic hit the United States, the FDA and the CDC had advised that N95 masks should not be reused. But to cope with the shortage, federal agencies have changed their recommendations. While some hospitals have the means to use UV light or a newly FDA-approved process using vaporized hydrogen peroxide, other medical centers might not. They most likely only have access to an autoclave or a similar device that can heat items while controlling both the temperature and the humidity.
It’s well established that high heat kills viruses. For instance, Middle East Respiratory Syndrome, or MERS, can be killed if exposed to a temperature of 149 degrees Fahrenheit (65 degrees Celsius) for more than 15 minutes, according to 2014 research conducted by Pasteur Institute, a prominent nonprofit research foundation based in Paris.
Masks have also successfully been sterilized of H1N1 using warm, moist heat, according to studies done in the 2010s by Applied Research Associates, a private research and engineering company.
But this coronavirus strain, SARS-CoV-2, is too new to have a fully vetted and peer-reviewed body of research. The Pasteur Institute is researching whether this new coronavirus can be killed with high heat, but the research won’t be finished for another several days.
Jean-Claude Manuguerra, a head researcher at the institute, said SARS-CoV-2 might not react to the same levels of heat in the same way. Killing this virus, compared to previous strains, could take more heat or even a longer amount of exposure.
“This is very different between viruses, and some viruses shed much more than others,” he said. “In the case of SARS-CoV-2, the shedding of the virus is much more than for SARS, which is down in the lung, and more also than MERS,”
For his research, Tsai is using numbers coming out of China, where the pandemic first broke out.
“Right after the outbreak, a lot of virologists did a lot of experiments, and they found 65 degrees Celsius [149 degrees Fahrenheit] for 30 minutes, that will kill COVID-19,” Tsai told VICE News.
The trick is finding the perfect temperature that kills the virus while not destroying the mask. Temperatures over 200 degrees Fahrenheit (100 degrees Celsius) would kill any virus — but would just about destroy an N95 mask. But Tsai said European certification requires a mask to be able to withstand 158 degrees Fahrenheit (70 degree Celsius) for up to 24 hours.
The masks are also electrostatically charged. That allows them to suck in and trap airborne particles that might contain viruses, rather than allowing those particles to spread or even enter a person’s body. Tsai, who invented that process, said the electrostatic charge can be undone if the mask is exposed to super high temperatures, which would make the mask less effective. But at just the right temperature, heating the masks could be a life-saver.
Scott Mechler, a mechanical engineer at the Massachusetts-based Consolidated Sterilizer Systems, said that tracks with research he’s conducting. Although his company isn’t working with active viruses, he said they have experimented on the temperatures at which face masks begin to break down.
“If you get up to about 100 to 120 degrees Celsius (212 to 248 degrees Fahrenheit), you start to see rapid degradation of the masks,” he said. “We've been focusing on trying not to damage the mask, and we've been using this number of 65 to 80 Celsius (149 to 176 Fahrenheit) for 30 minutes as kind of our gospel trying to achieve that, while not going over.”
But Mechler cautioned that the masks can only be reused three to five times if they’re disinfected in this way.
Cover image: Close-up of N95 respirator mask during an outbreak of COVID-19 coronavirus, San Francisco, March 30, 2020. (Photo by Smith Collection/Gado/Getty Images)