Covid-19 can pass between people up to THREE FEET apart even when they are wearing a mask as repeated coughing reduces their efficiency
- Researchers created a computer model to simulate saliva flowing from a cough
- They found that even with a mask droplets of saliva can still escape the mouth
- As people cough into the mask it becomes even less effective and lets out more
- They say this makes keeping the 6ft social distancing rule in place more vital
- Here’s how to help people impacted by Covid-19
Coronavirus is able to pass between two people standing just three feet apart even if one of them is wearing a surgical grade face mask, a new study warns.
Researchers from the University of Nicosia in Cyprus also found that masks became even less efficient when people repeatedly cough into them.
Scientists say the findings are ‘alarming’ – and underline the importance of keeping the 6ft distancing rule in place – even when masks are worn.
It comes as the Prime Minister, Boris Johnson, is under increasing pressure from industry, particularly the hospitality trade, to relax the distancing guidelines.
Scientists say the findings are ‘alarming’ – and underline the importance of keeping the 6ft distancing rule in place – even when masks are worn
Co-author Professor Dimitris Drikakis, of the University of Nicosia said a mask alone cannot prevent the transport of saliva droplets completely.
‘Many droplets penetrate the mask shield and some saliva droplet disease-carrier particles can travel more than 1.2 metres (4ft),’ he said – although most travel under 1 metre (3ft).
Face masks are believed to slow the spread of the pandemic but little is known about how well they work or under what conditions they won’t work.
The study, published in Physics of Fluids, found face masks can reduce transmission of airborne droplets – but not eliminate them completely.
Without a mask these droplets travel twice as far – so wearing one will help in reducing the risk of passing on the deadly disease.
However, repeated coughing, a symptom of coronavirus, reduces the efficiency of a mask and so more droplets are let through.
Previous work by the same team showed droplets of saliva can travel 18 feet in five seconds when an unmasked person coughs.
This time they used a precise computer model to map out their expected flow patterns when a mask-wearing person coughs.
They took into account potential weather conditions, air turbulence and even the skin and mouth temperature of the person coughing.
The researchers performed numerical simulations that account for droplet interactions with the porous filter in a surgical mask.
‘The results are alarming. Even when a mask is worn, some droplets can travel a considerable distance during periods of mild coughing,’ the authors wrote.
The tests were based on a standard surgical mask exhibiting initial efficiency of about 91 per cent when preventing droplets from escaping.
For visualisation purposes, the droplets were scaled up by a factor of 600 compared to their actual size – making them easier to track.
‘The droplet sizes change and fluctuate continuously during cough cycles as a result of several interactions with the mask and face,’ said Drikakis.
Co-author Dr Talib Dbouk said masks decrease the droplet accumulation during repeated cough cycles – effectively they get worse at stopping droplets escaping.
Researchers from the University of Nicosia in Cyprus also found that masks became even less efficient when people repeatedly cough into them
‘However, it remains unclear whether large droplets or small ones are more infectious,’ the co-author said.
They advised health care workers to wear much more complete PPE (personal protective equipment) when caring for a patient.
This should including helmets with built-in air filters, face shields, disposable gowns and double sets of gloves – changed regularly.
The researchers also urged manufacturers and regulatory authorities to consider new criteria for assessing mask performance that account for flow physics and cough dynamics.
Their earlier study published in the same journal in May found keeping 6ft apart may not be enough to protect against coronavirus.
Droplets carrying the potentially deadly bug can travel 18 feet in five seconds – even in the slightest of breezes.
Saliva is a complex fluid. It becomes suspended in a bulk of surrounding air when released by a cough.
The study has been published in the journal Physics of Fluids.