How many times can you really re-use an N95 mask?

N95 masks can be decontaminated up to 25 times and reused, something that can help when shortages occur.

During the start of the COVID-19 pandemic, there were severe shortages of PPE including N95 respirators. In the U.S., the Centers for Disease Control and Prevention and Occupational Safety and Health Administration (OSHA) released guidance regarding extended use and re-use strategies. 

The use of vaporized hydrogen peroxide (VHP) was explored as a way to decontaminate masks.

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A prospective cohort study was conducted at a large tertiary care academic center in Boston, Massachusetts from June 15 to Aug. 31, 2020 to determine mask effectiveness, filtration efficacy, and integrity over repeated decontamination processes. Results were published in the American Journal of Infection Control.

The decontamination process used in the study aligned with the manufacturer’s instructions for use and available FDA emergency use authorizations at the time.

“We sought to determine whether repeated VHP reprocessing would affect N95 respirator integrity as defined by qualitative and quantitative fit and filtration efficiency over 25 reprocessing cycles,” the study said.

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Function was defined as continued filtration efficiency greater than or equal to 95% of airborne particles with a diameter of 0.3-micron or more. Effectiveness was defined as passing a user seal check after every reprocessing cycle and retaining a good fit. Any reprocessed N95 masks that did not meet these measures were removed from the study.

The study used three male and four female participants who underwent qualitative and quantitative fit testing for N95 respirators. None had facial hair that could affect the seal one the mask was put on. 

The BioquellTM BQ-50 hydrogen peroxide vapor generator was used. After each VHP decontamination cycle, a seal check was done on the participants when they put on and removed their N95 mask. No physical cleaning of the masks was done. VHP reprocessing continued for 25 cycles.

All seven respirators underwent filtration efficiency testing for various particle sizes – first for narrow particle size range (0.3-0.375μm) and then a larger range (0.3-10 μm). This was assessed at baseline and after cycles 10, 15, 20, and 25, the researchers said.

In the end, all the N95 masks had passed the user seal checks, and filtration efficiency remained at greater than 95% throughout the study.

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