By TOMOYUKI SUZUKI/ Staff Writer
December 12, 2022 at 17:47 JST
Proper or lucky positioning on crowded escalators can help people significantly lower the risk of novel coronavirus infections caused by coughing maskless individuals, a study showed.
Standing behind a cougher on a descending escalator makes one less exposed to virus-laden droplets compared with standing behind the maskless individual while ascending, the study showed.
The result “can be applied to situations, such as in a train where people get on and off, and shopping malls,” said Masashi Yamakawa, a professor of computation fluid dynamics at Kyoto Institute of Technology, who led the study.
The research team’s study, titled “Numerical model for cough-generated droplet dispersion on moving escalator with multiple passengers,” was published in the November issue of Indoor Air, International Journal of Indoor Environment and Health.
The researchers simulated a situation in which men 175 centimeters tall stand on an escalator and a maskless man at the front of the line coughs.
The computer simulation covered both ascending and descending escalators, and it showed how droplets of 0.0009 to 1.5 millimeters spread from the cougher.
For both ascending and descending escalators, large droplets from the maskless cougher immediately fell to the stairs.
But on an ascending escalator, small droplets fell slightly, remained suspended near the original coughing point and behind the coughing person for a long period of time. The escalator moved people behind the coughing person up into area where the droplets were hovering.
On the descending escalator, small droplets immediately drifted upward and passed above the people behind. Only a small amount adhered to the people behind, according to the simulation.
The movements of the escalator and the riders complicated the surrounding aerial currents and influenced the droplets’ behaviors, the researchers said.
Keeping three steps between people reduces the infection risk on an ascending escalator better than standing one step apart, the team said.
The team hopes to continue such simulations “with a high degree of accuracy” to better prepare for the next pandemic, Yamakawa said.
He also said wearing a mask properly significantly reduces the risk of spreading or inhaling the droplets.
The findings can be read here: (https://onlinelibrary.wiley.com/doi/full/10.1111/ina.13131)
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An image shows how virus-laden droplets remain floating for around 10 seconds after a person on an ascending escalator at the front coughs. (Provided by Masashi Yamakawa, professor of computation fluid dynamics at Kyoto Institute of Technology)
