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Researchers in the US have found that in less than an hour, a rice cooker or similar device could sanitise an N95 mask and allow for it to be used again.
With face masks now a part of daily life, researchers have potentially found a way to extend the lifespan of one of the most in-demand mask types using something found in many people’s homes.
Writing in Environmental Science and Technology Letters, civil and environmental engineering professors Thanh ‘Helen’ Nguyen and Vishal Verma from the University of Illinois said it is possible to sanitise an N95 respirator mask in an electric cooker.
This could include rice cookers, they said, which can sanitise a mask in less than an hour, making the single-use mask reusable. N95 respirator masks are considered the gold standard of personal protective equipment, protecting the wearer against airborne droplets and particles such as the coronavirus that causes Covid-19.
“There are many different ways to sterilise something, but most of them will destroy the filtration or the fit of an N95 respirator,” Verma said.
“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 hypothesised 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.
What they found
Using one cooking cycle of an electric cooker at a temperature of approximately 100 degrees Celsius for 50 minutes, researchers found that the mask was decontaminated inside and out from four different classes of viruses, including a coronavirus type.
“We built a chamber in my aerosol-testing lab specifically to look at the filtration of the N95 respirators, and measured particles going through it,” Verma said. “The respirators maintained their filtration capacity of more than 95pc and kept their fit, still properly seated on the wearer’s face, even after 20 cycles of decontamination in the electric cooker.”
The researchers said that all tested viruses showed a reduction in integrity of the binding proteins and capsid proteins that form the shell around the viruses’ genetic material. This resulted in viruses being inactivated by at least 99.99pc during sterilisation.
In order for the process to work, the electric cooker must be run on a dry heat with no water inside. 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, but it is safe to stack a number of masks inside the cooker at the same time.
The researchers see potential for the electric-cooker method to be useful for healthcare workers and first responders, especially those in smaller clinics or hospitals that do not have access to large-scale heat sanitisation equipment.
