Face masks with breathing valves risk spreading coronavirus, Sage scientist warns

The public should stop wearing face masks with breathing valves as they risk spreading coronavirus particles, a Sage scientist has said.

The nation is beginning to adjust to the new normal of wearing face coverings on public transport, and inside shops from July 24, to prevent the spread of potentially infected droplets on to others.

But, it has been warned some varieties of masks may offer false protection as they let out breath via a valve.

Dr Ben Killingley, a consultant in acute medicine and infectious diseases at University College London Hospital, who sits on the Government's Scientific Advisory Group for Emergencies (Sage) committee said the public should not be wearing this style of mask if they want to stop their droplets escaping.

The FFP masks, also referred to as respirators, are highly effective at filtering particles coming in, providing protection for the wearer. But due to their tight fit a breathing valve is often fitted, meaning the wearer's breath is released.

These types of masks are commonly seen in medical settings to protect health workers from breathing in the viruses, or on construction sites to prevent workers breathing in dust particles.

"The idea of having a valve is that it's easier to breathe through," Dr Killingley said.

"When you breathe in, the valve is closed so that means that you're not breathing in anything from the air, but when you breathe out the valve opens a bit so it's a bit easier to breathe.

"They're absolutely fine to protect you from infection, but they're not generally recommended to stop stuff coming out.

"I think that is something that the public needs to know, that they shouldn't really be wearing a valved respirator if they're [wanting to stop] stuff coming out," he added.

Rishi Sunak, the Chancellor, was seen wearing a mask with a breathing valve on Wednesday, but Treasury sources told The Sunday Telegraph the valve was fitted with a filter, meaning Mr Sunak's breath was filtered before it was released.

Dr David Strain, Senior Clinical Lecturer at the University of Exeter Medical School, said: “Face masks with valves undermine the purpose of them as a population preventative strategy. They allow exhaled breath to come out directly with minimal filtration.

"Potentially infectious droplets are more likely to be passed on."

But he added that some masks are fitted with inserts into the valves to reduce the risk of droplets escaping and "these are indistinguishable by external appearance".