In a new study, researchers found owners of electric multi-cookers may be able to add another use to its list of functions: sanitization of N95 respirator masks.
They found that 50 minutes of dry heat in an electric cooker, such as a rice cooker or Instant Pot, decontaminated N95 respirators inside and out while maintaining their filtration and fit.
This could enable wearers to safely reuse limited supplies of the respirators, originally intended to be one-time-use items.
The research was conducted by a team at The University of Illinois, Urbana-Champaign.
N95 respirator masks are the gold standard of personal protective equipment that protects the wearer against airborne droplets and particles, such as the coronavirus that causes COVID-19.
A cloth mask or surgical mask protects others from droplets the wearer might expel, but a respirator mask protects the wearer by filtering out smaller particles that might carry the virus.
High demand during the COVID-19 pandemic has created severe shortages for health care providers and other essential workers, prompting a search for creative approaches to sanitization.
The team says there are many different ways to sterilize something, but most of them will destroy the filtration or the fit of an N95 respirator.
Any sanitation method would need to decontaminate all surfaces of the respirator, but equally important is maintaining the filtration efficacy and the fit of the respirator to the face of the wearer. Otherwise, it will not offer the right protection.
The researchers hypothesized that dry heat might be a method to meet all three criteria—decontamination, filtration, and fit—without requiring special preparation or leaving any chemical residue.
They also wanted to find a method that would be widely accessible to people at home. They decided to test an electric cooker, a type of device many people have in their pantries.
They verified that one cooking cycle, which maintains the contents of the cooker at around 100 degrees Celsius or 212 Fahrenheit for 50 minutes, decontaminated the masks, inside and out, from four different classes of the virus, including a coronavirus—and did so more effectively than ultraviolet light.
Then, they tested the filtration and fit.
They note that the heat must be dry heat—no water added to the cooker, the temperature should be maintained at 100 degrees Celsius for 50 minutes and a small towel should cover the bottom of the cooker to keep any part of the respirator from coming into direct contact with the heating element.
However, multiple masks can be stacked to fit inside the cooker at the same time.
The researchers see the potential for the electric-cooker method to be useful for health care workers and first responders, especially those in smaller clinics or hospitals that do not have access to large-scale heat sanitization equipment.
In addition, it may be useful for others who may have an N95 respirator at home—for example, from a pre-pandemic home-improvement project—and wish to reuse it.
The authors of the study include civil and environmental engineering professors Thanh “Helen” Nguyen and Vishal Verma.
The study is published in Environmental Science & Technology Letters.
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