A 50 minute cook cycle at 212 F in a dry electric multicooker decontaminates an N95 respirator without chemicals and without compromising filtration or fit. Credit: Chamteut Oh
Multiple electric range cooker owners can add another use to their list of functions, a new study suggests: disinfecting N95 respirators.
The University of Illinois, Urbana-Champaign study found that 50 minutes of dry heat in an electric cooker, such as a rice cooker or Instant Pot, decontaminated the N95 respirators inside and out while maintaining their filtration and fit. This could allow users to safely reuse limited supplies of respirators, originally intended to be single-use items.
Led by civil and environmental engineering professors Thanh “Helen” Nguyen and Vishal Verma, the researchers published their findings in the journal. Environmental science and technology charts.
N95 respirators are the gold standard of personal protective equipment that protects the user against airborne droplets and particles, such as the coronavirus that causes COVID-19.
Professor Helen Nguyen. Credit: L. Brian Stauffer
“A cloth mask or surgical mask protects others from droplets that the user can expel, but a respirator protects the user by filtering out the smallest particles that could carry the virus,” said Nguyen.
High demand during the COVID-19 pandemic has created a severe shortage of healthcare providers and other essential workers, prompting the search for creative approaches to disinfection.
A towel prevents the respirator from touching the heating element at the bottom of the pot. Credit: Chamteut Oh
“There are many different ways to sterilize something, but most of them destroy the leakage or fit of an N95 respirator,” Verma said. “Any disinfection method would need to decontaminate all surfaces of the respirator, but it is equally important to maintain the filtration efficiency and fit the respirator to the wearer’s face. Otherwise, it will not offer adequate protection. “
The researchers hypothesized that dry heat could be a method to meet all three criteria – decontamination, filtration, and adjustment – without requiring special preparation or leaving behind any chemical residue. They also wanted to find a method that was widely accessible to people at home. They decided to try an electric cooker, a type of appliance that many people have in their pantries.
They verified that a cook cycle, which keeps the contents of the pot at around 100 degrees Celsius or 212 Fahrenheit For 50 minutes, it decontaminated the masks, inside and out, of four different classes of viruses, including a coronavirus, and did so more effectively than ultraviolet light. Then they tested the filtration and fit.
“We built a chamber in my aerosol test lab specifically to observe the leakage of N95 respirators and measure the particles that pass through it,” Verma said. “The respirators maintained their filtration capacity of over 95% and maintained their fit, still seated correctly on the wearer’s face, even after 20 decontamination cycles in the electric range.”
The researchers created a video (included below) demonstrating the method. They point out that the heat should be dry heat: no water should be added to the pot, the temperature should be kept at 100 degrees Celsius for 50 minutes, and a small towel should cover the bottom of the pot to prevent any part of the respirator from entering. direct contact with the heating element. However, multiple masks can be stacked to fit inside the pot at the same time, Nguyen said.
The researchers see the potential for the electric cooker method to be useful for healthcare workers and first responders, especially those in smaller clinics or hospitals who do not have access to large-scale thermal disinfection equipment. In addition, it may be useful to other people who may have an N95 respirator at home, for example from a home improvement project before a pandemic, and want to reuse it, Nguyen said.
Reference: “Dry heat as a decontamination method for the reuse of N95 respirators” by Chamteut Oh, Elbashir Araud, Joseph V. Puthussery, Hezi Bai, Gemma G. Clark, Leyi Wang, Vishal Verma and Thanh H. Nguyen, July 15 2020, Environmental science and technology charts.
DOI: 10.1021 / acs.estlett.0c00534
The Environmental Protection Agency and the United States Department of Agriculture supported this work.
