Study: Small UV Device Can Disinfect N95s in a Minute

November 13, 2020
Frank Diamond

Investigators claim that their device can decontaminate N95s and surgical masks in the time it would take an infection preventionist to wash her hands.

In a normal year, the reuse of N95 and surgical face masks wouldn’t happen, but this has not been a normal year. When supplies of the masks ran short early on during the coronavirus disease 2019 (COVID-19) pandemic, they had to be reused and methods were sought to decontaminate them. Larger hospitals and healthcare systems have the capacity to use ultraviolet (UV) light to decontaminate face masks, but what about smaller hospitals or points of care such as a doctor’s office? Investigators with Case Western Reserve University School of Medicine think that they might have found the solution to this problem, according to a pre-print study in the American Journal of Infection Control.

They say that the UV radiation needed to inactivate 90% of single-stranded RNA viruses on gel can be anywhere from 1.32 - 3.20 mJ cm. This should also be enough to deactivate SARS-CoV-2 on face shields, though the investigators note that there’s no real consensus on this point yet. But because of their porousness, N95s and surgical masks (what the authors refer to as FFRs—filtering facepiece respirators) would require a UV dose of at least 1 Jcm.

“This relatively high required dose may make existing UVGI [ultraviolet germicidal irradiation] devices inefficient for decontamination in this context,” the study states. “For example, we previously described a protocol for the decontamination of FFR in biosafety cabinets available in academic laboratories. Achieving germicidal doses in these cabinets would require a minimum of 4.3 hours per-side, limiting the ease of use and throughput capacity of these devices for UVGI. These data are summarized in a recently released” US Centers for Disease Control and Prevention report.

The investigators developed what they described as a small-footprint UV-C tower device called the Synchronous UV Decontamination System (SUDS). They claim that SUDS can decontaminate N95s and surgical masks in the time it would take a healthcare provider, such as an infection preventionist, to wash her hands. SUDS is a small machine, small enough to fit on a nursing station counter, according to the study. It can hit all surfaces of the masks with more than 2 J cm, disinfecting them in less than a minute.

“Care providers could use our device to rapidly decontaminate their mask between patient encounters during standard handwashing protocols,” the study states. “Our proposed decontamination workflow using SUDS is as follows: 1) care provider doffs mask and places it in SUDS, 2) while SUDS runs, care providers can replace gloves and wash hands, 3) SUDS door opens automatically and care provider removes decontaminated mask. This workflow ensures that a care provider can continue using the same mask, which minimizes the need for re-fitting, and obviates the need for collection and dissemination.”

The study’s investigators note that other researchers have also concluded that UVGI is less likely to compromise the masks than bleach, microwave irradiation, and vaporized hydrogen peroxide, and various healthcare facilities have started using what the study calls “homebrew” UVIG devices.

“Many of the existing solutions, however, require collection and dissemination of masks to be decontaminated in batches’, adding logistical requirements to already busy workflows,” the study states. “Motivated by this, we designed the SUDS to fit directly into the workflow at the point-of-care to provide quick and easy decontamination of FFR.”