UCLA Scientists Test Decontamination Methods for N95 Respirators so They Can Be Used Again

Often used by healthcare workers treating patients with COVID-19 and designed to be used only once, N95 respirators can be effectively decontaminated and used up to three times, according to research by UCLA scientists and colleagues. Photo credit: CDC / Debora Cartagena

Scientists hope that new methods can alleviate the chronic shortage of personal protective equipment.

N95 respirators often worn by health care workers who are used to treat patients COVID-19 and are designed for single use only, research by UCLA scientists and colleagues has shown that they can be effectively decontaminated and used up to three times.

An early version of their study was published online. The full study is due to appear in the journal in September Emerging Infectious Diseases.

N95 respirators reduce exposure to airborne infectious agents, including SARS-CoV-2, the virus that causes COVID-19, and one of the most important pieces of personal protective equipment used by clinical workers to prevent the virus from spreading. Critical shortages in these masks have led to efforts to find new decontamination methods that can expand their uses.

“Although N95 respirators are designed to be used only before disposal, N95 respirators can be decontaminated and reused up to three times in times of shortage,” said James Lloyd-Smith, co-author of the study and UCLA Professor of Ecology and Evolutionary Biology. “But the integrity of the respirator seat and seal must be preserved.”

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In a controlled laboratory environment, the researchers tested various decontamination methods on small sections of the N95 filter fabric that were exposed to SARS-CoV-2. The methods involved vaporized hydrogen peroxide and dry heat at 70 degrees Celsius (158 degrees Fahrenheit), ultraviolet light and a 70% ethanol spray. All four methods eliminated detectable traces of viable virus from the N95 tissue test samples.

The researchers then treated completely intact, clean respirators with the same decontamination methods to test their durability if reused. Employees at the Rocky Mountain Laboratories of the National Institutes of Health in Montana volunteered to wear the masks for two hours to see if they were properly seated and face sealed. The scientists decontaminated each mask three times using the same procedure.

The masks treated with vaporized hydrogen peroxide showed no defects, suggesting that they could potentially be reused three times, Lloyd-Smith said. Those treated with ultraviolet light and dry heat showed problems with fit and sealing after three decontaminations, suggesting that these respirators could potentially be reused twice.

The study’s authors concluded that vaporized hydrogen peroxide was the most effective method because no traces of the virus could be detected after just 10 minutes of treatment. They found that ultraviolet light and dry heat are also acceptable decontamination methods, as long as the methods are used for at least 60 minutes.

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The ethanol spray, the scientists found, damaged the integrity of the fit and seal of the respirator after two sessions and is not recommended for decontamination of N95 respirators.

The researchers stressed that anyone decontaminating an N95 ventilator should carefully check the fit and seal of the face before each reuse.

Reference: “Effectiveness of the decontamination and reuse of N95 respirators against the SARS-CoV-2 virus” by Robert J. Fischer, Dylan H. Morris, Neeltje van Doremalen, Shanda Sarchette, M. Jeremiah Matson, Trenton Bushmaker, Claude Kwe Yinda, Stephanie N. Seifert, Amandine Gamble, Brandi N. Williamson, Seth D. Judson, Emmie de Wit, James O. Lloyd-Smith and Vincent J. Munster, June 3, 2020, Emerging Infectious Diseases.
DOI: 10.3201 / eid2609.201524

The study’s co-authors include Amandine Gamble, a UCLA postdoctoral fellow at Lloyd-Smith’s laboratory, and researchers at Rocky Mountain Laboratories, part of the National Institute for Allergies and Infectious Diseases at the NIH.

Funding sources included the National Institute of Allergy and Infectious Diseases, the Defense Advanced Research Projects Agency, and the National Science Foundation.

In a much-cited study in March, Lloyd-Smith and colleagues reported that the virus that causes COVID-19 remains on surfaces and in aerosols for several hours to days.

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