By Laura French
CHAMPAIGN, Ill. — A recent study found that household electric cookers can be used to safely sanitize N95 masks in less than an hour.
University of Illinois, Urbana-Champaign researchers 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, according to a university press release.
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 Letters.
“There are many different ways to sterilize something, but most of them will destroy the filtration or the fit of an N95 respirator,” Verma said in a statement. “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 for people at home. They decided to test an electric cooker, a type of device many people have in their pantries.
They verified that one cycle on their model's rice-cooking preset, which maintains the contents of the cooker at around 212 Fahrenheit for 50 minutes, decontaminated the masks, inside and out, from four different classes of virus, 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-testing lab specifically to look at the filtration of the N95 respirators, and measured particles going through it,” Verma stated. “The respirators maintained their filtration capacity of more than 95% and kept their fit, still properly seated on the wearer’s face, even after 20 cycles of decontamination in the electric cooker.”
The researchers created a video demonstrating the method. They note that the heat must be dry heat, with no water be added to the cooker, the temperature should be maintained at 212 Fahrenheit – or 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, Nguyen said.
The researchers see 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.
The Environmental Protection Agency and the U.S. Department of Agriculture supported the research.