April 2, 2020

Duke Health to Decontaminate N95s with Hydrogen Peroxide Vapor

A forthcoming paper in Applied Biosafety describes the efforts of scientists affiliated with the Duke University Health System to validate a method for decontaminating N95 respirators with vaporized hydrogen peroxide. The authors expect the method, if used in tandem with interim CDC guidelines for extending the working life of respirators, to help ease the strain on respirator supplies at Duke healthcare facilities during the COVID-19 pandemic. A pre-publication version of the paper (PDF) is available on the website of Duke’s Occupational and Environmental Safety Office.

While CDC has not approved any decontamination method for respirators, the agency has issued guidance that decontamination and reuse of respirators may be necessary to extend capacity during a crisis. CDC identifies vaporized hydrogen peroxide as a promising method, along with ultraviolet germicidal radiation and moist heat.

Duke conducted its decontamination trials in a special laboratory on the university campus. The laboratory, one of the regional biocontainment laboratories of the National Institute of Allergy and Infectious Diseases, contains a room designed for decontamination of laboratory equipment with hydrogen peroxide vapor.

The method described in the paper involves placing used respirators on racks and distributing a 35 percent hydrogen peroxide solution through the room until the concentration reaches 480 ppm. The respirators are “gassed” for 25 minutes, and the vapor is maintained in the room for an additional 20 minutes. Staff do not enter the room until the concentration falls below 1 ppm, the OSHA permissible exposure limit for hydrogen peroxide. The respirators are then removed from the room and allowed to sit for four hours to allow off-gassing of the hydrogen peroxide.

After trial runs, quality assurance checks and fit testing of the decontaminated respirators indicated that they were ready for reuse.

Some of the authors of the Applied Biosafety paper conducted a webinar March 31 to explain the method. Nicole Greeson, CIH, one of the paper’s authors, stated that Duke staff had conducted approximately 400 fit tests of decontaminated respirators and that all had passed.

Most Duke healthcare workers are on twelve-hour shifts, the authors said. Workers have been instructed to use a single N95 per shift. Afterward, they place their used respirator in containers, which are collected and delivered to the laboratory for decontamination. The decontaminated respirators are then put back into use.

The authors expect the combination of extended use and decontamination of respirators to extend the life of an N95 for up to two weeks.

A recording of the webinar is available online.