NIH Scientists Say N95 Masks Can Be Cleaned At Least 3 Times — But The FDA Is Allowing Up To 20

Scientists from the National Institutes of Health who started investigating the coronavirus back in January have weighed in on the safety of cleaning and reusing the coveted N95 medical masks.

In a study released this week, researchers found that it’s safe to clean and reuse the highly sought-after N95 respirator masks at least three times. But that raises questions about whether a new plan to decontaminate masks as many as 20 times at Boston hospitals is safe for medical workers depending on them amid the coronavirus equipment shortage.

“After three cycles of vaporized hydrogen peroxide treatment, the masks were still effective,” said Dr. Marshall Bloom, associate director for scientific management at the Rocky Mountain Laboratories in Hamilton, Montana. “It's possible that you could extend that, but it wasn't something that they looked at.”

Partners HealthCare facilities, including Massachusetts General Hospital and Brigham and Women’s Hospital, are using the hydrogen peroxide method, through a plant in Somerville. The Pentagon awarded Battelle, a Columbus, Ohio-based nonprofit, a $415 million contract for 60 of the decontamination machines nationally. The plan is to clean up to 80,000 masks per day at the Somerville site.

Rich Copp, a spokesman for Partners, said they are planning to clean and reuse masks five to 10 times, “but we’ll evaluate as the process moves forward.”

State and federal officials, as well as hospital representatives, are relying on the mask cleaning amid a critical shortage of masks and other gear to protect health care workers. Battelle has said the federal Food and Drug Administration approved the mask cleaning for emergency use, in part at President Trump’s urging.

But some prominent nurses’ groups have raised alarms about the safety of sterilizing and reusing masks that were intended only for single use in the past.

“None of this is OK. But if the NIH has tested it for three times, let's follow that,” said Judith Pare, director of the Division of Nursing Education and practice for the Massachusetts Nurses Association, which represents 23,000 nurses.

The NIH scientists studied three other decontamination methods as well — 70 degrees Celsius (158 degrees Fahrenheit) dry heat, ultraviolet light, and 70% ethanol spray. All four approaches cleaned the respirators, but some affected the mask’s important close fit.

They found that ethanol spray damaged the integrity of the mask’s fit and seal after two decontamination sessions. UV and heat-treated respirators began showing fit and seal problems after three decontaminations, leading them to conclude they should be cleaned only twice.

Some Massachusetts hospitals are using the UV cleaning method, including Children’s Hospital and UMass Memorial Medical Center.

The study's authors concluded that the vaporized hydrogen peroxide treatment being done in Somerville was most effective, “because no virus could be detected after only a 10-minute treatment.”

A spokeswoman for the state’s Department of Public Health had no immediate comment Thursday.

Martha Bebinger and Lisa Mullins contributed to this report.