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NIST studies use of UV for PPE disinfection

29 Mar 2022

Data could help define standards for future pandemics.

The use of ultraviolet illumination as a disinfection agent against Covid-19 became a theme during the pandemic, with UV wavelengths investigated for use cleaning both specific surfaces and the general atmosphere.

Research on the topic has included the development of new electrode materials to modify UV diodes, and ways to potentially recruit sources from home entertainment devices for the task.

Another focus has been testing whether UV could act as a disinfectant for the general environment, with a UK project researching the possibility of creating self-cleaning panels based around UV LEDs to reduce the spread of infections.

One particular interest is whether UV can adequately disinfect personal protective equipment (PPE) such as face masks, allowing the reuse of items which may be in short supply. NIST, the US National Institute of Standards and Technology, has now released the results of what it believes to be the most rigorous examination to date of UV light's effects on N95 respirator masks, the filtering masks commonly available to healthcare workers.

The study, published in NIST's Journal of Research, scrutinized UV-exposed N95 masks for traces of virus and looked for changes in the shape of their fibers, along with the ability of the masks to filter out aerosols and other properties.

"Right now, UV technologies are really in their infancy with respect to the health care environment," said NIST's Dianne Poster, a co-author of the study. "And the data in this paper could be really instrumental in building the foundation for these applications to become more routine."

Respond to the next emergency

NIST studied the use of UV-C illumination for the disinfection of N95 masks, using a commercial UV-C enclosure marketed for cleaning of non-critical and reusable equipment, although one not currently marketed for N95 disinfection and reuse. The project doused masks with a solution of OC43, a human betacoronavirus closely related to Covid-19. The masks were then irradiated with the cabinet's 19 252-nanometer sources for three minutes, 10 times each.

Examination of the masks afterwards showed that disinfection had taken place in all three layers of the mask, with the outer layers showing greater than 99-percent reduction of virus activity.

One key consideration for any proposed disinfection routine was whether the N95 masks were undamaged by the irradiation process, and remained physically able to filter viruses from the air as intended.

"Electron microscopy, flow resistance, tensile strength, and particle filtration metrology by NIST provided results to support the conclusion that the UV-C irradiation had no significant effect on the physical characteristics of the N95 masks," commented the project in its paper.

NIST anticipates that its findings could lead to a similar disinfection approach for other surfaces, such as blood pressure cuffs, fabrics, vinyls, and hospital privacy curtains - plus perhaps use in a future virus pandemic.

"UV standards developed through collaborations such as this could help us respond to the next emergency we encounter where the PPE supply chain is strained," said Dianne Poster.

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