Deactivating coronavirus on N95 respirators for reuse

Inner and outer view of an N95 mask between dry heat treatment cycles showing no deformation of the respirator. A thermocouple is affixed to the inner surface of the respirator with Kapton tape to measure the surface temperature of the mask over 10 heating cycles in a standard laboratory convection box oven. Masks are heat treated inside a self-sealing autoclave pouch (background) to prevent dispersion of viral particles from airflow inside the oven. Photos by Trevis Massey/LLNL.

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Thermal process to deactivate virus
The LLNL team is testing the efficacy of using 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, they are studying whether respirators retain functionality after thermal treatment.
Using a standard laboratory oven, the team conducted initial tests regarding how thermal treatment affects respirator components that play a key role in ensuring a secure fit on the user’s face, such as the metal nose clip, nose foam and neck straps. Following treatment, they tested the fit of the masks in LLNL’s respirator shop and identified thermal conditions that do not compromise the fit.
With these initial tests completed, the team is now studying deactivation efficacy. Using a mouse hepatitis virus that is related to SARS-CoV-2 but does not cause disease in humans, they are investigating whether any live virus remains on the filter of an N95 respirator after heat treatment. Following treatment, they 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 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 front-line health care workers need protection.”
The multidisciplinary research team includes materials scientists, biologists and engineers who rapidly came together during LLNL’s limited operations to study this challenge and provide results in an accelerated timeframe. In addition to Baxamusa, the team includes Mihail Bora, Monica Borucki, Eric Duoss, Kyle Fuhrer, Razi Haque, Travis Massey, Samuel Paik and Maxim Shusteff.