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University Study Reveals Usage Time And Effectiveness Of Covid Masks

Published on: 3 Sep, 2021
Updated on: 3 Sep, 2021

library image of a face masks to curb Covid-19 spread.

Air pollution experts at the University of Surrey have said respirator masks can be worn for up to 9.5 hours and be 97% effective in protecting against virus-laden particles such as Covid-19.

Medical face masks were comparable with respirators at up to 7.3 hours of usage time and around 81% effectiveness. But hand-made masks were the least effective at 47% but could be worn slightly longer at up to 8.8 hours, said researchers from Surrey’s Global Centre for Clean Air Research (GCARE).

Professor Prashant Kumar, founding director of GCARE, said: “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.

“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 our fight against Covid-19.”

In a paper published by the Journal of Hazardous Materials, 11 types of face protective equipment were tested including four respirators, three medical masks and four hand-made masks.

The study explored how long a mask could be worn and when it should be discarded, recycled or washed to optimise its usage time.

The GCARE team showed that over time the filters of a face covering started to become clogged by aerosol particles and breathing resistance increased. The crossover point between particle penetration and breathing resistance gave an estimate for how long a mask could be worn.

Detailed assessment of different size particles in the aerosols, combined with imaging from a scanning electron microscope, revealed material characteristics such as pore density, fibre thickness, filter material and the number of layers influenced the mask’s performance.

The  respirator masks provide the best performance with between 3.2 and 9.5 hours usage time and were around 97% effective.

Medical masks could be worn for between 2.6 and7.3 hours at around 81% effectiveness. Hand-made masks had a slightly higher usage time at between 4.0 and 8.8 hours but with a lot less protection at 47 per cent.

The study said factors such as the leakages due to their poor fitting, the wearer’s activity and the aerosol concentration levels in a setting such as indoor, outdoor, cars or trains affected the performance of the masks.

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