Lawrence Livermore National Laboratory is researching ways to rapidly decontaminate N95 respirator facemasks without compromising either their fit or their ability to filter airborne particles, so they can be reused during a pandemic.

As during the current COVID-19 pandemic, a shortage of personal protective equipment, including medical-grade surgical masks and respirators, can impede efforts to help infected patients and protect medical providers and first responders.

N95 respirators filter out 95% of airborne particles, as small as 0.3 micrometers, including viruses. Typically, N95 respirators are used only once in healthcare settings, before being disposed of, because they can become contaminated when treating infected patients.

Sal Baxamusa, who leads the LLNL team, said researchers are exploring ways to deactivate the virus that causes COVID-19 using and inexpensive method readily available in hospitals, as well as field settings, to ensure the availability of N95 respirators during a crisis.

“In health-care settings, it is always preferable to use an N95 respirator just one time,” Baxamusa said. “But in emergency situations, additional options may need to be considered.”

Liquid disinfectants like bleach can damage the filter, while sterilization methods that rely on ultraviolet light may not penetrate deep enough to fully decontaminate the filter. Sending used masks offsite to be decontaminated may not be practical during a crisis.

Instead, the LLNL team is testing the use of heat to penetrate the outer cover of a respirator and deactivate the virus on internal parts, including the filter, without affecting the respirators effectiveness.

The first challenge was to determine whether the heat-treated respirators would still provide a secure fit, including metal nose clip, nose foam and neck straps. The team is now studying the effectiveness of viral deactivation.

Using a mouse hepatitis virus that is related to the virus that causes COVID-19, but does not cause disease in humans, researchers are investigating whether any live virus remains on the filter of an N95 respirator after heat treatment. The treatment does not completely decontaminate all pathogens, but the research team anticipates that it can deactivate viruses.

“We are thrilled to be part of this effort to explore options for field-based reuse of respirators,” said Bob Maxwell, who leads LLNL’s Materials Science Division. “This type of solution would make it possible to safely reuse respirators during a pandemic, or any other situation where supplies are limited, and frontline health care workers need protection.”

The multidisciplinary research team includes materials scientists, biologists and engineers. In addition to Baxamusa, the team includes Mihail Bora, Monica Borucki, Eric Duoss, Kyle Fuhrer, Razi Haque, Travis Massey, Samuel Paik and Maxim Shusteff.