A study by the University of Erbana-Champaign showed that exposing N95 respirators in a multicooker to dry hot air for 50 minutes disinfects them inside and out without compromising their filtration capacity or damaging structural elements such as rubber straps. Such a method would allow multicooker owners to safely reuse limited supplies of disposable N95 respirators.
A team of researchers led by civil engineering and environmental engineering professors Thanh "Helen" Nguyen and Vishal Verma published their findings in Environmental Science and Technology Letters.
N95 Respiratory Masks are the gold standard for personal protective equipment that protects against aerosols and particles that spread the COVID-19 coronavirus.
“A cloth mask or surgical mask protects people from droplets that the mask wearer throws out when breathing (and also when sneezing and coughing). And the N95 respirator protects the wearer by filtering out even smaller particles from the inhaled air that can carry the virus, ”Nguyen said.
The high pressure on healthcare facilities during the COVID-19 pandemic has led to a severe shortage of healthcare workers and other essential workers, prompting creative approaches to sterilizing protective equipment for reuse.
“There are many different ways to sterilize anything, but most of them damage the filter material or destroy the design of the N95 respirator,” Verma said. “Any method of sterilization will require decontamination of all surfaces of the respirator, but it is equally important to maintain air filtration efficiency and a snug fit of the respirator to the face. Otherwise, the respirator will not provide adequate protection. "
The researchers hypothesized that dry hot air might be a method that meets all three criteria - decontamination, maintaining the effectiveness of the mask's filter material, and not interfering with the mask's ability to fit snugly to the face. And this method does not require preliminary special preparation of the mask and does not leave any chemical residues on the mask. They also wanted to find a method that was widely available at home. They decided to test the multicooker - a device that many people have at home.
Their study confirmed that the multicooker used in the study, in one cycle of the Cooking Rice program, which maintains a temperature of about 100 degrees for 50 minutes, decontaminates the mask inside and outside from four different classes of viruses, including coronavirus - and does it more efficiently. than ultraviolet light.
They then tested the filtering efficiency of the mask material and the mask's ability to fit snugly to the face after this treatment.
“In my aerosol testing lab, we built a chamber specifically to investigate the filtration efficiency of N95 respirators and measure the particles passing through it,” Verma said. "The respirators retained their filtering capacity by more than 95% and retained their shape - still fixing properly on the face, even after 20 disinfection cycles in a multicooker."
Researchers have posted a video demonstrating this decontamination method. They point out that heating should be dry - no water is added to the pan, the temperature should be kept at 100 degrees Celsius for 50 minutes, and a small towel should cover the bottom of the pan so that the respirator doesn't have direct contact with the heating element. At the same time, according to Nguyen, several masks can be placed on top of each other so that they are processed inside the multicooker at the same time.
Researchers see the potential benefits of using the multicooker method for healthcare workers, especially in small clinics or hospitals that do not have sufficient air sterilizers. It can also be useful for those who have an N95 respirator at home and want to reuse it, Nguyen said.
This study was supported by the Environmental Protection Agency and the USDA.