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Why Distancing and Masks are Not Enough to Protect The Public

Timothy Boyer Ph.D.'s picture
COVID-19 travels further and stays afloat longer in air than previously believed.

A new study says that masks and distancing are good practices, but not good enough to protect the public—and here’s why.


A new study collaboration involving fluid dynamics experts from Vienna University Of Technology, the University of Florida, the Sorbonne in Paris, Clarkson University (USA) and the MIT in Boston have published their findings in the International Journal of Multiphase Flow stating that although it makes sense to wear masks and encourage social distancing, that science shows this may lull the public into a false sense of security. In truth, they found that currently used data supporting distancing and masks is actually outdated, and that current recommendations are not enough to adequately protect the public.

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According to the news release:

"Our understanding of droplet propagation that has been accepted worldwide is based on measurements from the 1930s and 1940s", says Prof. Alfredo Soldati from the Institute of Fluid Mechanics and Heat Transfer at TU Wien. "At that time, the measuring methods were not as good as today, we suspect that especially small droplets could not be measured reliably at that time."

In previous models, a strict distinction was made between large and small droplets: The large droplets are pulled downwards by gravity, the small ones move forward almost in a straight line, but evaporate very quickly. "This picture is oversimplified," says Alfredo Soldati. "Therefore, it is time to adapt the models to the latest research in order to better understand the propagation of COVID-19."

What the researchers found was that a more modern view of fluid dynamics shows that droplets are actually traveling through a multiphase flow where while the particles are liquid, they are actually traveling in a gas.

“Small droplets were previously considered harmless, but this is clearly wrong," explains Soldati. "Even when the water droplet has evaporated, an aerosol particle remains, which can contain the virus. This allows viruses to spread over distances of several meters and remain airborne for long time.”

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One of the problems with distancing is that even though you may carefully avoid coming near others, the fact is that viral particles can remain in the air as long as 15 minutes, allowing you to unwittingly walk into a fog of infection.

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The authors of the study liken this to a situation where an elevator—although empty when you enter—may have been used by an infected person just minutes earlier and not be safe. Other environments, such as closed-in meeting rooms and restaurants, would have the same potential infectious conditions as the hypothesized elevator.

The importance of their research is that fluid dynamics mathematical modeling can be used to pinpoint a more accurate risk assessment and potentially be used to help develop protections more effective than distancing and masks—such as ways to provide protective ventilation in businesses like restaurants and aircraft.

"Masks are useful because they stop large droplets. And keeping a distance is useful as well. But our results show that neither of these measures can provide guaranteed protection," says Soldati.

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"Until now, political decisions on COVID-protection measures have mainly been based on studies from the fields of virology and epidemiology. We hope that in the future, findings from fluid mechanics will also be included," says Alfredo Soldati.

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Timothy Boyer has a Ph.D. in Molecular and Cellular Biology from the University of Arizona. For 20+ years he has been employed as a freelance health and science writer. Today, with an eye on the latest news, Timothy continues writing about science with a focus on what you need to know for healthier living. For continual updates about health, you can also follow Timothy on Twitter at TimBoyerWrites.

Image Source: Courtesy of Chetraruc from Pixabay


COVID-19: Distancing and Masks are not Enough” Vienna University Of Technology news release 20 Oct. 2020.

Host-to-host airborne transmission as a multiphase flow problem for science-based social distance guidelines” S. Balachandar et al., International Journal of Multiphase Flow, Vol. 132, Nov. 2020.