Research shows conversation quickly spreads droplets more than six feet inside buildings

Monday, Oct 5, 2020

By John Sullivan, Office of Engineering Communications

With implications for the transmission of diseases like COVID-19, researchers have found that ordinary conversation creates a conical, “jet-like” airflow that quickly carries a spray of tiny droplets from a speaker’s mouth across meters of an interior space.

“People should recognize that they have an effect around them,” said Howard Stone, the Donald R. Dixon ’69 and Elizabeth W. Dixon Professor of Mechanical and Aerospace Engineering at Princeton University. “It’s not just around your head. It is at the scale of meters.”

Although scientists have not yet fully identified the transmission mechanisms of the COVID-19 virus, current research indicates that people without symptoms could infect others through tiny droplets created when they speak, sing or laugh. Stone and co-lead researcher Manouk Abkarian, of the University of Montpellier in France, wanted to learn how widely and quickly exhaled material from an average speaker could spread in an interior space.

“Lots of people have written about coughs and sneezes and the kinds of things you worry about with the flu,” Stone said. “But those features are associated with visible symptoms, and with this disease we are seeing a lot of spread by people without symptoms.”

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