Study identifies three effective methods to sanitize N95 respirators for reuse

Bethesda, MD — Three methods to decontaminate N95 filtering facepiece respirators for reuse are being recommended by the National Institutes of Health after researchers at the agency successfully tested their effectiveness and the repeat functional integrity of the respirator after each sanitization.

To help preserve the supply of N95s in the health care industry during the COVID-19 pandemic, the researchers tested small sections of N95 filter fabric that had been exposed to the coronavirus that causes COVID-19 using four decontamination methods: vaporized hydrogen peroxide, 70° C dry heat, ultraviolet light and 70% ethanol spray.

“All four methods eliminated detectable viable virus from the N95 fabric test samples,” an April 15 NIH press release states.

The researchers then treated “fully intact, clean respirators” with the same decontamination methods to test their reuse durability. Volunteers wore the masks for two hours to determine if they maintained a proper fit and seal over the face; decontamination was repeated three times.

Vaporized hydrogen peroxide proved to be the most effective decontamination method, as no virus could be detected after only a 10-minute treatment. Further, the respirator showed no failures during the integrity testing process, suggesting it could be reused three times.

UV light and dry heat were acceptable methods as long as they were applied for at least 60 minutes, and the respirator began showing fit and seal issues after three decontaminations, leading to the conclusion that it could be reused only twice.

Ethanol spray, on the other hand, damaged the integrity of the respirator’s fit after two decontaminations, so is not recommended by NIH.

Anyone using decontamination methods to reuse N95 respirators is advised to check the fit and seal before each reuse.

The study, which has not undergone a peer review but was released to assist in the public health response to COVID-19, was published online April 15 by medRxiv, an online archive and distribution server for complete but unpublished manuscripts in the medical, clinical and related health sciences.