LOS ANGELES – Disposable N95 respirators can be decontaminated and reused, according to research announced Thursday by UCLA scientists.
N95 respirators reduce exposure to airborne infectious agents, including SARS-CoV-2, the virus that causes COVID-19, and are one of the key features of personal protective equipment used by clinical workers in preventing of the spread of the virus. Critical shortages of these masks have prompted efforts to find new decontamination methods that can expand their use.
An early version of the study was published online by the Centers for Disease Control and Prevention, with the full study appearing in the journal Emerging Infectious Diseases in September.
“Although N95 respirators are designed for only one use for disposal, in times of shortage, N95 respirators can be decontaminated and reused up to three times,” said James Lloyd-Smith, co-author of the study and a UCLA Professor of Ecology and Evolutionary Biology. “But the integrity of the fit and seal of the respirator must be preserved.”
In a controlled laboratory environment, the researchers tested several decontamination methods on small sections of N95 filter material exposed to SARS-CoV-2. The methods included evaporated hydrogen peroxide, dry heat at 70 degrees Celsius – 158 degrees Fahrenheit – ultraviolet light and a 70% ethanol spray. All four methods eliminated detectable viable virus from the N95 dust test trials.
The researchers then treated completely intact, clean respirators with the same decontamination methods to use their durability. Employees at the Rocky Mountain Laboratories of the National Institutes of Health in Montana volunteer to apply the masks for two hours to determine if they maintain a good fit and seal over the face. The scientists decontaminated each mask three times, using the same procedure with each.
The masks treated with vaporized hydrogen peroxide did not experience any failures, suggesting that they could potentially be used three times, Lloyd-Smith said. Those treated with ultraviolet light and dry heat began to see problems and sealing problems after three decontaminations, suggesting that these respirators could potentially be reused twice.
The authors of the study concluded that evaporated hydrogen peroxide was the most effective method because no traces of the virus could be detected after only a 10-minute treatment. They found that ultraviolet light and dry heat are also acceptable decontamination procedures, as long as the methods are applied for at least 60 minutes.
The ethanol spray, the scientists discovered, damaged the integrity of the fit and seal of the respirator after two sessions, and they do not recommend it for disinfecting N95 respirators.
The researchers emphasize that anyone who decontaminates an N95 respirator should check the fit before using it again over the face.
