NIH Study Details Methods for Decontaminating N95 Respirators

The study has not been peer-reviewed yet, but the findings have been released to assist the public in responding to COVID-19.

N95 respirators are a critical piece of protective equipment for health care workers responding to cases of coronavirus disease 2019 (COVID-19). However, the respirators are designed for single use and with coronavirus cases continuing to climb throughout the United States, these protective tools are in short supply.

A new study conducted by scientists with the National Institutes of Health (NIH) had concluded that N95 respirators can effectively be decontaminated and maintain “functional integrity” for up to 3 uses.

The NIH announced the findings in a statement today in conjunction with a pre-print, but caution that they are not yet peer reviewed. The study was conducted in a controlled laboratory setting and are being shared to assist in the response to COVID-19.

The study was conducted by a team with the NIH’s Rocky Mountain Laboratory in Hamilton, Montana which is a part of the National Institute of Allergy and Infectious Diseases, in collaboration with a team from the University of California, Los Angeles.

The teams tested the decontamination of small sections of N95 filters that were previously exposed to SARS-CoV-2. They tested a number of methods including vaporized hydrogen peroxide, 70-degree Celsius dry heat, ultraviolet light, and 70% ethanol spray.

Following the decontamination process, the investigators found that all 4 methods eliminated detectable virus from the N95s. Next, they treated clean respirators with the same decontamination methods to evaluate durability. For this, employees volunteered to wear the masks for 2 hours to determine if they maintained proper fit and seal.

The decontamination process was then repeated 3 times for each mask using the same procedure.

During this stage, the study team observed that ethanol spray damaged the fit and seal of the N95 after 2 rounds of decontamination; therefore, it is not recommended to use ethanol spray. It was also observed that respirators treated with UV and heat started show fit and seal problems following 3 contaminations. As such, it is suggested that masks treated with these methods of decontamination can be re-used twice.

There were no observed failures with the vaporized hydrogen peroxide treated masks, suggesting that they can be re-used 3 times. Based on this, the authors concluded that this is the most effective decontamination method for N95 respirators. The authors caution anyone who decontaminates an N95 respirator to check the fit and seal prior to each re-use.