WEARING a used face mask can be worse than not wearing one at all, a new study has claimed.
Researchers specifically looked at the three-layer surgical masks, which are commonly worn among healthcare professionals.
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They found that when the masks are worn for the first time the can filter out nearly three-quarters of tiny particles that stay in the air and are most responsible for infection.
However, if that same mask is used more than once they only filter out one-quarter of the tiny droplets because the masks become deformed with each wear.
The researchers, from the University of Massachusetts Lowell and California Baptist University, say their findings are evidence of why a mask shape should be considered when looking at protection and designing new masks.
Co-author Dr Jinxiang Xi, an associate professor of biomedical engineering at UMass Lowell, said: "It is natural to think that wearing a mask, no matter new or old, should always be better than nothing.
"Our results show that this belief is only true for particles larger than five micrometers, but not for fine particles smaller than 2.5 micrometers."
The three-layer masks are among the most recommended to protect yourself and others from contracting Covid-19.
The inner layer is made from an absorbent material, the middle layers acts as a filter and the most outer later is made from a non-absorbent material.
For the study, which was published in the journal Physics of Fluids, the team developed a computer model of an individual wearing a surgical mask with pleats.
They then looked as the behavior of the tiny liquid droplets and particles that linger in the air.
The model was able to track where those droplets and particles landed on the mask and the face and if they travelled in to the nose or lungs.
Their model showed that when people wear face masks, it changes the way the air flows around the face.
The team found that air does not enter through the nose and mouth at specific points but through the entire mask surface at low speeds.
When they looked at how the three-layer filtration worked, the researchers found that new masks can filter 65 per cent of particles.
However, if it a used mask it can only filter out 25 per cent.
The team believes this happens because the pleats in the mask affect airflow patterns and when they are used more than once it can change shape and diminish its efficiency.
The researchers believe this is because the pleats of the surgical mask affect airflow patterns and, when used over and over again, they change shape and their efficacy diminishes.
Xi added: "We hope public health authorities strengthen the current preventative measures to curb COVID-19 transmission, like choosing a more effective mask, wearing it properly for the highest protection, and avoid using an excessively used or expired surgical mask."
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