LLNL Investigating Inexpensive Methods for Sterilizing and Reusing N95 Masks

Dentistry Today
Photo by Trevis Massey/LLNL


Photo by Trevis Massey/LLNL

Lawrence Livermore National Laboratory (LLNL) is studying ways to safely and rapidly remove viral threats from N95 respirators without compromising the device’s fit and its ability to filter particles so they can be reused.

N95 masks typically are used once in healthcare settings because they can be contaminated when treating infected patients, posing a risk to caregivers who continue wearing them as well as to other patients treated by the provider. The pandemic, then, has resulted in N95 shortages.

Interdisciplinary LLNL researchers including materials scientists, biologists, and engineers are exploring ways to deactivate the SARS-CoV-2 virus on N95 respirators by using inexpensive tools that are readily available in hospitals and field settings to ensure their continued availability.

“In healthcare settings, it is always preferable to use an N95 respirator just one time. But in emergency situations, additional options may need to be considered,” said Sal Baxamusa, who is leading LLNL’s research team.

LLNL is studying deactivation techniques that rapidly remove the viral threat without compromising the way the respirator fits on the user’s face and without leaving toxic residue that could harm users.

For example, liquid disinfectants like bleach can damage the filer, and sterilization methods that rely on ultraviolet light do not penetrate deep enough to full decontaminate the filter. Also, sending masks offsite to a central location with sophisticated decontamination equipment might not be practical during a crisis when respirator supply is limited.

LLNL is testing the efficacy of a thermal process where heat penetrates through the outer cover of the respirator to deactivate the virus on internal parts, including the filtering element. At the same time, LLNL is studying whether respirators retain functionality after thermal treatment.

Using a standard laboratory oven, LLNL conducted initial tests regarding how thermal treatment affects respirator components that ensure a secure fit on the face, such as the metal nose clip, nose foam, and neck straps. Following treatment, researchers tested the fit of the masks in LLNL’s respirator shop and identified thermal conditions that don’t compromise fit.

With these initial tests completed, LLNL is now studying deactivation efficacy. Using a mouse hepatitis virus that is related to SARS-CoV-2 but does not cause disease in humans, LLNL is investigating whether any live virus remains on the filter of an N95 respirator after heat treatment.

Following treatment, LLNL will gently remove viral particles from the material and count the number of infectious particles that are present. While thermal treatment does not completely decontaminate all pathogens, the researchers said, they anticipate 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 healthcare workers need protection,” said Maxwell.

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