Develop operating standards for UV disinfection of N95 masks without compromising performance

In 2020, amid supply shortages, medical institutions across the U.

Now, researchers at the National Institute of Standards and Technology (NIST) have conducted perhaps the most rigorous examination yet of the effects of UV light on N95 masks, showing that the masks can be disinfected with little or no effect on their shape or function

This result represents a critical step toward designing a UV standard that could have far-reaching benefits in the future

Dianne Poster, a research chemist and senior advisor at NIST, said: "Currently, UV technology is in its infancy in the health care setting

N95 masks are effective against infectious respiratory diseases

When COVID-19 first broke out in the U.

UV-C has been used for decades to remove bacteria and viruses from air, water and surfaces, and its applications are supported by scientific research

To better understand how UV-C can be used to sterilize N95 masks, NIST partnered with UV-Concepts (a manufacturer of UV-C systems that are not currently marketed for N95 sterilization) and ResInnova Laboratories (an antimicrobial testing company)

The authors of the new study attached N95 masks to a shelf within the UV-Concepts system -- a housing made up of 19 UV-C lamps and painted them with a reflective surface, then irradiated them with UV light for 3 minutes, 10 each of 10 times

The team soaked some masks in a solution containing OC43, a human coronavirus that is a close relative of the virus that causes Covid-19

But N95 masks, sanitized or not, depend only on their ability to work

"The UV-C wavelengths used to inactivate viruses are not known to produce chemicals like ozone, which destroys the plastic in N95 masks

The authors performed extensive testing on N95 masks to see if radiation altered their entire or even individual fibers

To prevent the effects of UV light beyond what the microscope can see, the authors looked elsewhere for potential changes

Wright said the researchers measured how resistant the masks were to the air flowing through them to see if UV light would make N95 masks harder to inhale

The NIST team also examined whether the irradiation affected the filtering ability or mechanical properties of the N95

Meanwhile, experts at the National Institute for Occupational Safety and Health (NIOSH), part of the Centers for Disease Control and Prevention, have also studied N95 masks exposed to radiation in enclosures
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But despite using different methods to study some of the same mask properties as the NIST team, as well as some different aspects, such as mask fit, they came to the same conclusion
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In the future, researchers and members of the UV industry can use the authors' data to gain an initial understanding of how different levels of UV-c radiation affect the performance and cleaning of N95 masks, which is necessary to standardize these methods
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What's more, the study shows the benefits of collaboration when standard approaches are limited and many specialists, capabilities and facilities across disciplines are required
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"Personally, as a private, independent laboratory, I found it very rewarding to be able to work with federal agencies and manufacturers on this project," said study co-author and President and CEO of ResInnova Labs Officer Matthew Hardwick said
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"UV standards developed through collaborations like this can help us deal with the next emergency we encounter when the PPE supply chain is strained," Poster said
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