A group of researchers said they have used the Fugaku supercomputer to demonstrate that wearing masks is effective in suppressing the spread of exhaled airborne droplets at such places as in karaoke rooms, outdoors and in taxis.
The team from the Riken research institute, Kobe University and other entities announced Thursday the results of calculations verifying the spread of droplets containing the novel coronavirus in such places. The computer has shown that the spread of the virus was controlled by wearing a mask.
The karaoke scenario presumed nine people in a 21-cubic-meter room where the air is freshened about twice as fast as in an office.
When one person started singing, small aerosol droplets spread into the room in about 30 seconds. The amount of aerosol droplets that escaped from a mask was about a third the amount exhaled by a person without a mask.
The open-air situation was simulated with 10 people gathering around a 60-by-120-centimeter table at a barbecue. When a person spoke loudly without a mask, another person standing one meter in front of the speaker was exposed to about 10% of the total airborne droplets exhaled.
When there was a weak wind of 0.5-1.0 meters per second -- less than 4 kph -- the droplets also reached the people downwind. However, when the person spoke wearing a mask, the airborne droplets barely reached the others at all.
The study also found that by using the fresh air mode of a taxi's air conditioner while the car was running, the air inside the car would be replaced within 1-1/2 minutes. However, opening windows of about 5 centimeters did not provide adequate ventilation.
As droplets dispersed by coughing tend to linger inside a car, taxi drivers and their passengers are required to wear masks.
As there is a system of constantly changing air inside an aircraft, the diffusion of airborne droplets is almost completely suppressed even if a mask-wearing passenger coughs inside the plane.
"We're going to analyze the risk of infection by re-creating situations to see how viruses from inhaled airborne droplets attach inside a body, so that we will be able to show effective countermeasures," Kobe University Prof. Makoto Tsubokura said.
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