Droplets from coughing can travel more than 6 feet outdoors and have the potential to be a greater transmission risk for shorter adults and children, a new simulation study found.

The study published in the peer-reviewed journal Physics of Fluids used models to simulate cough droplets’ trajectory when someone coughs outdoors with someone else nearby. Researchers from Singapore’s Agency of Science, Technology and Research ran a simulation with varied air temperatures, drop sizes, humidity, wind speed and distances between the person coughing and the person listening.

The researchers found that despite the cough droplets having low inhalation exposure, it could lead to the virus spreading to clothing or skin, which could then result in infection if someone touches their face, mouth or nose. They wrote that it could be a potentially higher risk for children and shorter adults who are less than 3 feet away from someone coughing.

“Young children may be at greater risk compared to adults based on the typical downward cough trajectory. Teenagers and short adults are advised to maintain a social distance greater than 2 m. from taller persons,” researchers wrote in the study. “Surgical masks are known to be effective at trapping large droplets and therefore recommended for use as necessary.”

More on the COVID-19 pandemic

COVID-19 can spread through small particles or respiratory droplets, including from when an infected person sneezes, coughs, or breathes, according to the CDC. Infection can result when the particles are inhaled through the mouth and nose.


The study found that when there is a wind speed of about 2 yards per second or around 4 miles per hour, droplets the size of 100 micrometers or 1,000 micrometers can travel 21.6 feet and 4 feet, respectively.

Wind also has an impact on how far droplets can travel. A 100-micrometer droplet can travel 3 feet without wind and around 22 feet with a wind speed of around 6.7 miles per hour.

In May, another study published in the Physics of Fluids found wind could carry droplets 18 feet outdoors.


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