Wearing any face mask reduces the distance travelled by a person's breath by more than 90 per cent and could prove vital in stopping the spread of coronavirus, new research has shown.
Scientists at the University of Edinburgh have tested several types of masks, including home-made face coverings, and found all offered some form of protection.
But the researchers discovered that dangerous particles still escape into the air unless any coverings are fitted properly and medical-grade.
People in England are being advised to wear masks on public transport, but the Government has so far stopped short of introduced any compulsory measures on face coverings.
The public health advice in Wales is that they may provide a marginal benefit to others around the mask wearer. Scotland's advice is that they provide "limited" benefits, while face masks are recommended in Northern Ireland.
France has introduced €135 fines to anyone not wearing face coverings on the Metro lines and buses. Similar measures are being enforced in New York and other European countries.
The London Mayor London Sadiq Khan has said the UK Government should follow suit and enforce stricter laws on face masks.
Dr Ignazio Maria Viola, from the University of Edinburgh, co-ordinated the research.
He said: “I have generally been impressed by the effectiveness of all the face coverings we tested.
“However, we discovered that some face coverings allow the emergence of downward or backward jets that people are not aware of and that could be a major hazard to others around them.”
ITV News visited the Edinburgh lab earlier in May where tests were being conducted on face masks
Foreign Secretary Dominic Raab said last week that face coverings "don't really have much of an impact" in protecting the wearer, but they can "provide an incremental mitigation" of the risk to other people.
Scientists in Edinburgh used computer technology to test seven types of masks, which allowed them to measure the distance and direction travelled by air when a person breathes or coughs.
Even face covering without an outlet valve reduced the distance by at least 90 per cent.
Dr Felicity Mehendale, a surgeon at the Centre for Global Health at the University of Edinburgh’s Usher Institute, said: “It was reassuring to see the hand-made mask worked just as well as the surgical mask to stop the wearer’s breath flowing directly forwards.
“This suggests that some hand-made masks can help to prevent the wearer from infecting the public. But, 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.”
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