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Stanford University has recently released a summary of what is known about the re-use of N95 face masks in anaesthetics.

The key findings are:

“It is unknown how wearing the same mask multiple times effects the fit of N95 masks [US National Institute for Occupational Safety and Health (NIOSH)]
• NIOSH states “there is no way of determining the maximum possible number of safe reuses for an N95 respirator as a generic number to be applied in all cases” and advise to “discard N95 respirators following use during aerosol generating procedures.”
• Some methods of N95 mask disinfection can maintain filtration efficiency. Their effect on mask fit is unknown, and these methods are not approved by NIOSH.”

The methods of decontamination are summarised as:

“In summary bleach and microwaves were failures at point of care because the bleach gases (skin and respiratory irritants) remained after multiple strategies were used to remove them, the microwave melted the masks and soaking them first led to reduced filtration. EtO, UVGI, and hydrogen peroxide decontamination were safe and effective in the models tested but it is not known if they would retain filtration, material strength, and airflow integrity with repeated use. EtO, UVGI, and hydrogen peroxide limitations include time from decontamination to reuse and available space and materials to decontaminate in an OR setting. 70C /158F heating in an oven for 30min, or hot water vapor from boiling water for 10 min, are additional effective decontamination methods.”


The full paper can be viewed here: