Health care workers wear N95 respirator masks to keep themselves safe while caring for people with infectious diseases such as COVID-19.

These masks were designed for only one use. But early study results from research by the National Institutes of Health (NIH) have found that the masks can be decontaminated and potentially reused up to three times.

"To test mask safety, NIAID researchers first exposed the masks to SARS-CoV-2, the virus that causes COVID-19, and then to various cleaning treatments."

The study was led by researchers at NIH's Rocky Mountain Laboratories in Montana, part of the National Institute of Allergy and Infectious Diseases (NIAID). To test mask safety, NIAID researchers first exposed the masks to SARS-CoV-2, the virus that causes COVID-19, and then to various treatments, including ultraviolet (UV) light, an alcohol spray, dry heat, and vaporized hydrogen peroxide. They decontaminated each mask three times. 

Volunteer lab workers separately tested masks that were not exposed to the virus but were decontaminated by the four treatments. The workers wore masks for two hours to make sure that they still fit properly after decontamination.

All of the treatments removed the virus from the masks, but some worked better than others.

The study found that the hydrogen peroxide treatment was the most effective and that it could remove the virus from the mask fabric after 10 minutes of treatment. The masks treated with hydrogen peroxide also still fit and sealed over the face properly, suggesting that they could potentially be reused up to three times. Both the UV and heat-treated masks showed problems with fit and seal after three treatments. This suggests that masks treated with these methods could potentially be reused twice.

Unlike the other treatments, the alcohol spray damaged the mask's fit and seal after only two cleanings. So the researchers do not recommend using it for N95 respirators. They also urge health care workers who decontaminate N95 masks to check the fit and seal before each reuse.

The Centers for Disease Control and Prevention says that the general public should not wear N95 masks because they are critical supplies that must be reserved for health care workers. However, cloth face coverings are recommended for general use to help prevent the spread of COVID-19. To clean cloth facing coverings, machine wash and dry them regularly.