How to sanitise N95 masks; here's the best way

Owners of electric multicookers may be able to add another use to its list of functions, as it can sanitize N95 respirator masks, say researchers. This could enable wearers to safely reuse limited supplies of the respirator masks originally intended to be one-time-use items.

The study published in the journal 'Environmental Science and Technology Letters' found 50 minutes of dry heat in an electric cooker such as a rice cooker or Instant Pot, decontaminated N95 respirator masks inside and out, while maintaining their filtration and fit.

"There are many different ways to sterilize something, but most of them will destroy the filtration or the fit of an N95 respirator," said study researcher Vishal Verma from the University of Illinois in US.

"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," Verma added.

The right way to sanitize N95 masks

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. 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 cooking cycle, which maintains the contents of the cooker at around 100 degree Celsius or 212 Fahrenheit for 50 minutes, decontaminated the masks, inside and out, from four different classes of the virus, including 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 said.

"The respirators maintained their filtration capacity of more than 95 per cent and kept their fit, still properly seated on the wearer's face, even after 20 cycles of decontamination in the electric cooker," he added.

The researchers created a video demonstrating the method. They noted that the heat must be dry heat -- no water added to the cooker, the temperature should be maintained at 100 degree 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.

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 that do not have access to large-scale heat sanitization equipment.