The researchers found that dry heat treatment of the N95 mask can kill four types of virus, including the coronavirus. Thus, after processing, they can be reused.
Scientists from the University of Illinois at Urbana-Champaign came to such a discovery. They suggest processing medical protective masks in household electric cooker for 50 minutes at 100 degrees. First of all, we mean protective respirators N95, but in this way it is possible to disinfect reusable masks of other types.
The study — published in Environmental Science & Technology Letters, a peer-reviewed journal — joins a growing body of research that has emerged during the pandemic that evaluates the efficacy of kitchen appliances as a sanitation tool. In February, a team from Chung Shan Medical University in Taiwan found that dry-steaming surgical masks in a rice cooker for several minutes had a sterilizing effect, the Taipei Times reported. Taiwan’s health minister later demonstrated the technique at a Central Epidemic Command Center news conference. More recently, scientists in Ohio suggested in April that steaming masks in rice cookers could also be effective — a finding that aligns with guidance from the Centers for Disease Control and Prevention on reusing N95 respirators, which lists “moist heat” as a promising method of decontamination.
To guide their experiments, the researchers turned to 3M’s suggestions for reusing its respirators, which draw on recommendations from the CDC and other federal agencies, according to the study. The company states that an effective decontamination technique must inactivate the target virus without negatively affecting the mask’s fit and filtration ability or leaving behind a residue from dangerous chemicals.
To evaluate the effectiveness of the method, the researchers placed the mask in a Electric Cooker 15 cm high, 22 cm in diameter and 5.7 liters in volume. No water was added to the bowl, a small towel was placed on the bottom so that the mask would not melt on contact with the bottom. In the intervals from 5 to 13 minutes, the temperature of the surface of the multicooker bowl and the temperature on the surface of the mask were measured using an infrared thermometer.
“The manufactured model of the Electric Cooker gives complete information about how viruses are destroyed, how the filtration of small particles passes through the mask, and how normal gas exchange is maintained when air passes through the fabric of the mask by 95%,” said Verma. “Moreover, after 20 cycles of disinfection, the layers of the mask retained their original functions.”
After warming up the masks, the researchers assessed their integrity based on two criteria: determining the degree of permeability of particles through the mask surface and the insulating properties of the mask associated with its fit to the face.
According to the results of the experiment, the method of sterilizing the mask using dry heat allows you to almost completely suppress the activity of the Tulane virus, rotavirus, adenovirus, infectious coronavirus. The virus particles are no longer active both on the surface and inside the mask. The degree of impermeability of the mask was 95%, the masks retained their shape after 20 disinfection cycles for 50 minutes in an Electric Cooker or oven. At the same time, no matter how many masks are sterilized at the same time, this does not affect the final result.
Scientists are confident that such a sterilization method meets the main criteria for sanitation: disinfection, filtration and sufficient air intake into the human respiratory tract without any additional devices and reagents.
Still, Nguyen touted her team’s results.
“We looked for a method that is easy to use, not expensive, not involving chemicals,” she said. “As long as you make sure you don’t have moisture, as long as you can measure temperature and keep the same exposure time, it is very likely to work.”
For more clarification checkout study’s FAQ page.