HOMEMADE face masks can stop the spread of deadly coronavirus – but can also generate "intense backward jets", experts say. 

Researchers from the University of Edinburgh put seven types of Covid-19 face masks to the test, including surgical masks, respirators, lightweight and heavy-duty face shields, and handmade masks.

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And they found that all of the face coverings, apart from those with a valve, reduced the forward flow of exhaled breath by at least 90 per cent.

However, the researchers also discovered that they produce "intense backward jets" whenever someone coughs or breathes heavily.

It comes after the Government urged Brits to wear face coverings while out of the home – and unveiled step-by-step guides on how to make face coverings at home using old T-shirts.

The researchers put the masks to the test using a special type of imaging to detect the distance and direction travelled by the air that is expelled when someone coughs or breathes heavily.

'Far-reaching leakage jets'

Measurements were taken from people wearing different face masks from people standing or lying down, as well as from a manikin connected to a cough-simulating machine.

They found that while the surgical and handmade masks did limit the forward flow of an outward breath, they also generated "far-reaching leakage jets to the side, behind and above and below".

And "intense backward jets" generated whenever someone was coughing or breathing heavily.

Meanwhile, full-face shields worn without a mask enabled "a strong downward jet" to be released.

Respirator masks, commonly used by workers exposed to fine dust, were also found to offer protection – but valves on these masks designed to make breathing easier "could potentially allow infectious air to spread considerable distances in front".

The researchers said that only masks that form a tight seal with the face were able stop the escape of virus-laden fluid particles.

When it comes to making homemade masks, Brits are being urged to "ensure it seals gaps around the face, but be careful because making something that obstructs the mouth and nose is always dangerous".

The University of Edinburgh says its findings could help steer official guidance on wearing masks to help combat coronavirus, which can be transmitted in small droplets of moisture in people's breath.

It is important to seal all gaps otherwise air will be projected at high speed in directions that we cannot control

Dr Ignazio Maria Viola, who headed-up the study, told Sky News that he had "generally been impressed by the effectiveness of all the face coverings we tested".

And he added that scarves offer similar protection in limiting the spread of Covid-19 – although they are not ideal and "might not be very popular in the summer".

He said: "Firstly, you need to have multiple layers to make it effective, and second it is important to seal all gaps (hence it should be tightish) otherwise air will be projected at high speed in directions that we are not aware of and that we cannot control. I also guess that it should be washed after every use."

Dr Viola warned any new decisions on policy should bear in mind that people could end up having a false sense of security when wearing face coverings – meaning they fail to observe social distancing.

And he added that another risk lies in the "potential transmission route through touching a mask that has been infected and thus transferring the virus from the mask, to your hands, to other surfaces".

Dr Felicity Mehendale, a surgeon at the Centre for Global Health, added that it was "reassuring to see the handmade mask worked just as well as the surgical mask to stop the wearer's breath flowing directly forwards".

Despite this, she added: "The strong backward jets mean you need to think twice before turning your head if you cough while wearing a mask, and be careful if you stand behind or beside someone wearing a mask."

Earlier this month, Brits were told to wear face coverings in public to prevent the spread of coronavirus.

Strong backward jets mean you need to think twice before turning your head if you cough while wearing a mask

Boris Johnson said that homemade masks should be worn in enclosed spaces where social distancing isn’t possible or where you may come into contact with people from outside of your household.

It includes public transport and in some shops, the Prime Minister's 50-page roadmap to get the UK out of lockdown revealed.

The Department of Health said that after considering the latest scientific advice from Sage, face coverings can help reduce the spread of Covid-19.

Advice from Sage

They stressed that the evidence shows face coverings can stop you passing coronavirus on to others, if you are asymptomatic or have yet to develop symptoms.

It's unlikely they will stop you catching the bug.

TfL also said all passengers and staff would need to wear masks on the Underground, and advised people avoided busy times.

No 10 stressed that face coverings could include scarves and homemade masks – and added surgical masks used as vital PPE should be left for NHS and healthcare workers.

The guidelines state that children under the age of two should not wear masks, nor should anyone who may find it difficult to manage them safely. This includes primary age children and those with respiratory conditions.

The Government also warned that for face coverings to be effective, people must wash their hands before putting them on and taking them off.

Masks aren't necessary if you're outside, while exercising, at schools or in offices.


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