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A video shared on the UK prime minister’s Twitter account has been called out by medical professionals for featuring a face mask with a valve on it.
The animated video, published on Tuesday, explains how the guidance on face coverings in England is changing from 24 July, when it will be mandatory to wear a face covering in shops and supermarkets, as well as on public transport.
While the video gets across the important message that “your face covering must cover your nose and mouth at all times”, it doesn’t do the best job educating people on the right type of mask to wear, argue health experts.
Halfway through, an animated man can be seen wearing a face mask that appears to have a valve on it. The caption reads: “By wearing a face covering, you are protecting others and slowing the spread of the virus.”
But masks with valves have been banned in some cities and counties in America because they don’t protect other people from the wearer’s germs.
The guidance on face coverings in England is changing.— UK Prime Minister (@10DowningStreet) July 14, 2020
From 24 July, it will be mandatory to wear a face covering in shops and supermarkets, as well as on public transport.
Your face covering must cover your nose and mouth at all times. pic.twitter.com/qKKqNDSAu5
Experts say the one-way valve closes when a person breathes in and opens when they breathe out. This means while the valve doesn’t let germs in, protecting the wearer, it does allow a person’s exhalations to leave the mask – and therefore does not protect others and slow the spread of the virus.
Professor Trisha Greenhalgh, an expert in primary care at University of Oxford, tells HuffPost UK the government “need to change” the video.
“The valve acts like an exhaust pipe, potentially spewing germs out to the environment,” she says. “Cloth face coverings are the best thing. They stop droplets – that’s why they get wet of course, and you have to change them when they do.
“Droplets contain viral particles so the more droplets get caught in your face covering, the fewer germs get into the air. A valved mask bypasses the barrier and potentially emits the droplets in an explosive gas cloud!”
Dr Nisreen Alwan, associate professor in public health at the University of Southampton, responded to 10 Downing Street’s tweet to say: “The graphic is wrong. Don’t use a mask with a valve because it pushes air out and doesn’t protect others. Use any cloth face covering over mouth and nose.”
Earlier this month, Dr Bharat Pankhania, a senior clinical lecturer at the University of Exeter Medical School, urged people to stop wearing masks with valves in them. He told LBC they force a “high velocity flow of air from the mouth out through the valve which could create a plume of infection”.
“Wearers can propel, much further, the very droplets we are trying to capture within the mask,” he said.
Clear messaging on face masks is crucial for the adoption of wearing face masks and coverings by the general public, a study by the University of Oxford found. But so far, the messaging has been anything but.
The 10 Downing Street Twitter account has since shared a new video featuring a face cover which doesn’t have a valve on it.
Face coverings help slow the spread of #coronavirus.— UK Prime Minister (@10DowningStreet) July 15, 2020
Wear one in public places and make sure it covers your nose and mouth at all times.
Exemptions include young children, people with breathing difficulties and people living with a disability.https://t.co/6Jltlo0YDy pic.twitter.com/YRRAQRTN2J
At the time of writing, the video featuring the mask with the valve hadn’t been removed.
HuffPost UK has contacted 10 Downing Street for comment and is waiting to hear back.
This article originally appeared on HuffPost and has been updated.