Respirators may be disinfected up to 20 times without loss of fit or filtration

Jacqueline Mitchell 617-667-7306; jsmitche@bidmc.harvard.edu

JULY 02, 2020

Respirators may be disinfected up to 20 times without loss of fit or filtration

Boston – The COVID-19 pandemic has resulted in an international shortage of N95 respirators, the traditionally single-use, virus-filtering face masks that are essential to protecting health care workers from infection. As infection rates begin to spike in some regions around the country, a team of microbiologists from Beth Israel Deaconess Medical Center identified an efficient, low-cost method of disinfecting N95 respirators for re-use up to 20 times. Their findings, which could help alleviate shortages among health care providers, are published online in mBio.

“One of the greatest threats to health care workers’ well-being is the critical shortage of personal protection equipment—N95 respirators in particular,” said James E. Kirby, MD, Director of the Clinical Microbiology Laboratory at BIDMC. “Given the contemporary limitations of the supply chain, it is imperative to identify effective means of decontaminating, reusing, and thereby conserving N95 respirator stockpiles.”

Kirby and colleagues set out to identify a low-cost, widely accessible decontamination method that simultaneously provides maximal decontamination and imparts minimal structural damage to the N95 respirators. Using a less deadly, but much harder to kill virus known as a bacteriophage virus as a stand-in for the virus that causes COVID-19, the team contaminated N95 respirators with the model virus. Next, they placed the contaminated masks in a 110- or 150-watt microwave oven, evaluating various configurations of common household items, such as coffee mugs, sandwich bags and rubber bands for ease and efficiency of killing the virus with steam heat generated by the oven.

The scientists found that the optimal configuration consisted of a quarter of a cup of water in the bottom of a glass container with a large enough opening to expose the entire N95 respirator to the column of steam generated by the oven’s heat. With the container covered by mesh from a produce bag and secured by a rubber band, the scientists placed the respirator on top of the mesh and then ran the oven for one minute increments.

Subsequent testing revealed dramatic reduction in the amount of model virus remaining—an average of more than 99.999 percent reduction—after three minutes in the microwave.

Kirby and colleagues next examined the respirators’ fit and function after one, five or 20 three-minute treatments in the microwave using all seven exercises of the United States’ Occupational Safety and Health Administration’s (OSHA) fit test protocol. They found no structural or functional issues with the respirators.

“Safe and effective decontamination of N95 respirators protects health care workers and maintains the health care system’s capacity to handle incoming patients,” Kirby said. “The ability to re-sterilize the respirator at least 20 times without detriment to filtration or fit provides a compelling disinfection method that should prove generally accessible to health care workers in diverse settings, including outpatient practices, frontline providers, and remote clinical settings.”

Study co-authors included Katelyn E. Zulauf, Alex B. Green, Robert Seeley, and Alana Dale of BIDMC; Alex N. Nguyen Ba, Tanush Jagdish, and Dvir Reif of Harvard University. Zulauf was supported by the National Institute of Allergy and Infectious Diseases training grant (T32AI007061). The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.

About Beth Israel Deaconess Medical Center

Beth Israel Deaconess Medical Center is a part of Beth Israel Lahey Health, a new health care system that brings together academic medical centers and teaching hospitals, community and specialty hospitals, more than 4,000 physicians and 35,000 employees in a shared mission to expand access to great care and advance the science and practice of medicine through groundbreaking research and education.