According to a new study led by Western University, the globally recommended and recognized six-foot physical distancing rule – to prevent the spread of COVID-19 – may not make much of a difference if someone coughs right in your direction.
The findings were recently accepted for publication in the journal Indoor Air.
For the study, Eric Savory from Western’s Department of Mechanical and Materials Engineering manufactured a ‘cough chamber’ to analyze expulsive airflows (coughs) produced by human subjects, who were naturally infected with seasonal influenza.
Savory and his collaborators found that if you are standing unobstructed six-feet away from someone who coughs, the resulting droplets will reach you within three seconds and they will continue to projectile forward well beyond the recommended six feet.
“Even when you are 2.5 metres (eight feet) away, the airflow in the cough can still be moving at 200 millimetres a second,” explains Savory, who worked with virologists at Sunnybrook Hospital in Toronto for the final analysis. “That means the very fine droplets are going to remain suspended for a long time, even after four seconds.”
The study shows that approximately 10 per cent of the cough droplets originally expelled are still in the air at a distance of six feet (1.8 metres).
Western Engineering’s cough chamber is a two-metre enclosed cube with an opening and chin rest in the front, which is used as an access point for study participants to cough. Within the cube, a camera and a laser are used to determine the velocity of the expelled droplets from the cough.
And while the physical testing was conducted up to and including the 2017-18 flu season, long before the global outbreak of COVID-19, the study provides valuable data and analysis to government officials and healthcare workers around the world currently fighting the spread of the deadly disease.
Savory, who believes this study marks the furthest distance anyone has ever measured cough airflow, is now transitioning his findings specifically to the COVID-19 pandemic.
Collaborating with Eric Arts from Western’s Schulich School of Medicine & Dentistry and Franco Berruti from Western’s Department of Chemical and Biochemical Engineering, the interdisciplinary research team intend to examine the pathways of COVID-19 droplets through the air and analyze different material surfaces in order to verify its survivability under different temperature and humidity conditions.
This further investigation will be conducted in Western’s ImPaKT containment laboratory where Arts and his collaborators are actively developing an effective COVID-19 vaccine.
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