Dry heat generated from electric cookers, such as rice cookers or pressure cookers, can be used to sanitise N95 masks, according to a study by the University of Illinois at Urbana-Champaign.
This could allow the in-demand respirators, originally meant to be single-use items, to be safely reused, researchers posited.
Civil and environmental engineering professors Thanh “Helen” Nguyen and Vishal Verma, who led the research, published their study titled “Dry Heat as a Decontamination Method for N95 Respirator Reuse” in the Environmental Science And Technology Letters journal.
The researchers said that dry heat maintained 100°C for 50 minutes can effectively deactivate a number of viruses without damaging the fit and filtration of the N95 mask.
“We found that the dry heat generated by an electric cooker (100°C, 5% relative humidity, 50 min) effectively inactivated Tulane virus (TV, >5.2-log10 reduction), rotavirus (RV, >6.6-log10 reduction), adenovirus (AdV, >4.0-log10 reduction), and transmissible gastroenteritis virus (TGEV, >4.7-log10 reduction),” the researchers said in their study.
It added: “The respirator integrity (determined on the basis of the particle filtration efficiency and quantitative fit testing) was not compromised after 20 cycles of a 50min dry heat treatment.”
Hence, the researchers believed that the method of dry heat decontamination through electric cookers can be used as an “effective and accessible” method for the safe reuse of N95 respirators.
Due to Covid-19, the study explained that the N95 mask has become an essential part of the personal protection equipment (PPE) worn by healthcare workers. It added that PPE shortage has forced some healthcare providers to reuse N95 masks.
According to the World Health Organisation in a guide on the rational use of PPE, N95 masks is recommended for healthcare workers involved in aerosol-generating procedures such as bronchoscopy and sputum induction on Covid-19 patients.
In a YouTube video to demonstrate the decontamination method, researchers began by placing a towel in the pot to cover the bottom – direct contact with the heating element and the high heat it produces will damage the mask – and then placed the N95 mask on top of the towel.
Depending on the size of the cooker, several masks can be stacked on top of each other and disinfected at the same time.
Researchers cautioned viewers not to add any water into the cooker as only dry heat is needed. After completing the cooking process, the mask is ready to be used again.
For other materials such as the commonly-used three-ply mask, researchers said further studies are needed as “different materials may require different temperatures and treatment times to produce the same treatment result”.
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