Summarised by Centrist
New research from the University of Massachusetts Amherst challenges the widely accepted six-foot (approx. 2 metres) social distancing rule, revealing it offers limited protection in indoor queues.
The study shows that typical indoor temperatures between 72°F and 86°F (22.2°C and 30°C) create conditions where infectious breath particles linger at face level, increasing the risk of airborne disease transmission.
This happens because air currents generated by people’s stop-and-go movement produce competing forces that trap aerosols near breathing zones rather than dispersing them.
Laboratory experiments and computer simulations demonstrated that faster walking speeds and more extreme temperatures help push particles away from faces, reducing infection risk. Yet in the standard comfort temperature range, warm exhaled breath rises while walking-induced downwash currents push particles downward, resulting in a suspension of infectious aerosols at head height.
Researchers found that physical distance, including the standard six feet, has only a minor effect on aerosol spread in moving lines.
“Depending on the walking speed, an intermediate temperature range can potentially heighten the infection risks by allowing the breath plume to linger; however, colder and warmer ambients both suppress the spread,” the study said. Senior author Varghese Mathai added, “There are no hard-and-fast rules about social distancing that will keep us safe or unsafe. The fluid dynamics of air are marvelously complex.”
