Research reveals optimal usage time and effectiveness of different face masks

Dec 17, 2023

Source: Ingimage

Respirator masks have been hailed as the "go-to" face covering to mitigate Covid-19, according to new research from the University of Surrey.

A new study, published in the Journal of Hazardous Materials today, explored the effectiveness of 11 masks, including four respirators, three medical and four handmade face coverings, within a submicron range.

"Our research aims to give the general public clear and accurate information so they can make informed decisions"

Prashant Kumar

The laboratory investigation, carried out by air pollution experts at the university, also sought to uncover how long a mask should be worn.

Researchers from the university's Global Centre for Clean Air Research (GCARE) developed a filter testing rig to measure the filtration performance of different face mask materials.

Findings showed that, over time, the filters of a face mask can start to become clogged by aerosol particles, while breathing resistance also increases as the masks are worn.

Those behind the study used the crossover point between the time at which particles penetrated the mask and breathing resistance, to estimate an ideal usage duration for the different types of face coverings.

Results showed that respirator masks were 97% effective in protecting against virus-laden particles and should be worn between 3.2 to 9.5 hours for maximum effectiveness.

Meanwhile, medical face masks gave between 2.6 to 7.3 hours of usage time and were around 81% effective, said the researchers.

In addition, handmade face coverings were found to be effective for four to 8.8 hours and 47% effective against virus-laden particles.

Professor Prashant Kumar, senior author of the paper and founding director of GCARE, said: "It is important to reiterate that while vaccination is key to the fight against Covid-19, face coverings are also essential.

"Donning a face mask is not only about protecting yourself but all those around you," he noted.

"While any face mask is better than no face mask, our research aims to give the general public clear and accurate information so they can make informed decisions as we continue in our fight against Covid-19," added Professor Kumar who is also associate dean at the university.

The researchers highlighted that the effectiveness of masks was measured based on a continuous filtering of air that typically had the aerosol concentrations found in a roadside environment.

Therefore, they expected that in practice, when factors such as the level of activity of wearers and different aerosol concentrations levels were accounted for, a mask's usage time could increase "appreciably".

Over the course of the coronavirus pandemic, leading unions have been calling for higher-grade personal protective equipment (PPE) for nurses and colleagues, to ensure they are protected against the virus and its new more transmissible variants.

Updated national guidance published in June, stated that respiratory PPE, such as FFP3 masks, should no longer be limited to staff in areas where aerosol-generating procedures take place.

But unions said the change did not go far enough and wanted to see a more "precautionary approach" adopted for the workforce.

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