(CNN) The N95 respirator masks that health care workers need to protect themselves while treating coronavirus patients are in dangerously short supply.

So much so that physicians are wearing used respirators , risking infection to care for patients.

But now, Duke University researchers have developed a method to clean them so they can be safely re-worn.

The team at the Duke Regional Biocontainment Laboratory has already decontaminated hundreds of N95 respirators without damaging them so they can be re-worn several times. It could provide significant relief for hospitals running low on supply

The researchers published their decontaminating protocol so other hospitals can follow their lead.

Using vaporized hydrogen peroxide, the researchers can kill microbial contaminants that lurk on the masks after they're worn.

It's a method labs have used for decades to decontaminate equipment, said Wayne Thomann, director emeritus of the Duke Occupational & Environmental Safety Office.

But the team never thought they'd need it for face masks.

How they do it

Decontaminating requires special equipment in a closed facility to handle the hydrogen peroxide. But the process has already been carried out at Duke Health hospital complexes and can occur at other hospitals, too.

The team can clean up to 500 masks in one cycle , which takes over four hours. They're working to expand that capacity.

Previous research showed that the respirators could be decontaminated and re-worn between 30 to 50 times, but Thomann and the biocontainment lab crew are still evaluating how often they can be re-worn after treating coronavirus patients.

"It will certainly be less than 30, and we will be conservative to ensure performance and safety," Thomann told CNN in an email.

The masks tolerate the decontamination well, he said, so the process doesn't damage them or make them less effective.

Before redistributing the respiratory masks, the team inspects them for tears to make sure they haven't lost their shape -- they must fit snugly and cover the entire mouth to be effective.

N95 masks are essential to fight coronavirus

Personal protective equipment (PPE) like respirator masks, eye masks, gloves and gowns are essential for health care workers treating coronavirus patients. The virus is primarily transmitted through respiratory droplets -- meaning spit, coughs and sneezes -- and any workers caring for those patients are routinely exposed to the virus.

And if physicians and nurses are sickened, there are fewer people to care for patients.

N95 respirators aren't meant to be re-worn. The Centers for Disease Control and Prevention recommends physicians dispose of them after each patient encounter or when the respirator doesn't form an effective seal against the mouth and nose.

But with respirator supplies dwindling , medical professionals have already started reusing them, risking their own safety.

Decontaminating them keeps physicians fighting the coronavirus safer and bolsters hospitals' efforts to treat patients, Thomann said.

"The N95 respirator is the most appropriate respiratory protection for patient care personnel attending Covid-19 patients, particularly performing aerosol-producing procedures on those patients," he told CNN. "Reprocessing helps us ensure they will have the best PPE to protect them."