Standing three steps apart on an escalator significantly reduces the risk of COVID-19 infection while it is safer to descend than ascend one, recent research by a team involving the Kyoto Institute of Technology showed.

The team lined up 10 maskless men, each 175 centimeters tall, on an escalator and computed the dispersion of droplets assuming that the man at the front coughed. The traced droplets measured less than 1.5 millimeters.

The research showed that on a descending escalator, the droplets were quickly blown upward and traveled over the heads of the others.

But on an ascending one, the droplets fell to a level around the waist of the coughing man and remained in the air for a long time.

"It is important to keep a distance as human movements make (surrounding) airflow unsteady and cause the dispersion of droplets," said Masashi Yamakawa, a professor at the Kyoto institute who led the team. The research was published in the scientific magazine Indoor Air in November.

While the study assumed that those riding the escalator did not wear masks, the dispersion of droplets would be reduced significantly if they were worn properly, he said.


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