Industrial microwaves could make face masks reusable in hospitals

face masks in hospitals
The finding could increase supply and reduce waste in hospitals. Source: mohamed_hassan (via Pixabay)
The team at Cardiff University showed that 90 seconds of exposure could make respirators and face masks reusable in hospitals.

By Holly Giles | Deputy Editor 

Researchers from Cardiff University have been testing the ability to use industrial microwave ovens to decontaminate personal protective equipment (PPE) including respirators and surgical masks in order to make them reusable.

In the study the researchers tested respirators against three different microwave disinfection cycles and then afterwards, checked their ability to filter bacteria and viral-sized aerosols to check they still worked as PPE. The team reported their findings in the Journal of Hospital Infection, where they showed that some respirators can be decontaminated in just 90 seconds of exposure in an industrial-grade oven. 

This finding is important in helping combat demand for PPE as many hospitals have reported difficulty is accessing respirators and surgical masks over the course of the pandemic. It is also thought this finding could reduce the environmental impact of the pandemic; one estimate suggests that if all the UK wore single-use masks each day for a year it would create 66,000 tonnes of waste and 57,000 tonnes of plastic packaging. Current estimates state that 129 billion face masks are being disposed of every month of the COVID-19 pandemic so any technique to reduce this number is definitely welcomed.

“Being unable to access adequate PPE puts frontline workers and patients at risk of contracting coronavirus. Whilst masks are usually considered to be single use items, we wanted to find out whether they could be safely disinfected and used again,”

said co-author of the study Prof Jean-Yves Maillard, from the School of Pharmacy and Pharmaceutical Sciences.

Whilst this was successful for some respirators, microwaving surgical masks was shown to remove their aerosol filtering capacity meaning the masks no longer worked. Michael Pascoe, co-author of the study from the School of Pharmacy and Pharmaceutical Sciences, said:

“Surgical masks are known to lose effectiveness once they become moist – we suspected that microwave disinfection would lead to a similar loss in their ability to filter aerosols and this was confirmed by our lab observations.”

The team then built on this using dry heat instead and showed that exposure to 70°C dry heat for 90 minutes was effective at decontaminating both surgical masks and respirators. After three dry heat cycles, both types of mask retained their aerosol filtering properties.

This research may have important implications in hospital settings in increasing supply of PPE to staff and reducing waste, but researchers have highlighted that this cannot be transferred to a domestic setting. 

Professor Adrian Porch, from the School of Engineering, said:

“Domestic microwave ovens typically have much lower power, around 800 W, and use rotating turntables rather than a rotating antenna. Significantly longer exposure times would be needed to achieve similar results and it is unknown how this would affect the functioning of the mask. Masks which contain thin wires can even catch fire when placed in a microwave.”

This is not a technique to try at home but may help our key workers in fighting the virus and keeping them safe. The research from Cardiff University is expected to be implemented into hospitals as the pandemic progresses.


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