According to a new study by the University of Illinois, Urbana-Champaign- 50 minutes of dry heat in an electric cooker, such as a rice cooker or Instant Pot, could effectively sanitize N95 respirator masks. It could decontaminate 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.
A type of respirator, an N95 mask, offers more protection than a surgical mask does because it can filter out both large and small particles when the wearer inhales. In the COVID-19 pandemic, the N-95 Masks become personal protective equipment that protects the wearer against airborne droplets and particles.
Vishal Verma, the co-author of the study, said, “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.”
According to scientists, dry heat might be a method to meet all three criteria—decontamination, filtration, and fit—without requiring special preparation or leaving any chemical residue.
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.
Verma said, “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. 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.”
Scientists created a video demonstrating the method. They note that the heat must be dry—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.
Scientists 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. Also, 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.
- Chamteut Oh et al., Dry Heat as a Decontamination Method for N95 Respirator Reuse, Environmental Science & Technology Letters (2020). DOI: 10.1021/acs.estlett.0c00534