COVID Face Shields No Match for Sneeze Vortex Rings

Sneeze COVID Face Shield

Face shields alone are not highly effective in preventing COVID-19 infection.

Face shields worn alone are not effective against COVID-19 sneezes.

Do face shields provide enough protection to the wearers against COVID-19 if they don’t also wear a mask? Spoiler alert: no. But researchers at Fukuoka University in Japan are working to create face shields safe enough to be worn alone.

The researchers originally set out to explore whether surgical masks and face shields used as preventive measures are effective, as well as to determine if the stress of wearing an N95 surgical mask for long periods could be reduced.

In Physics of Fluids, from AIP Publishing, Fujio Akagi and colleagues describe their work to gain a better understanding of what happens to the airflow around a face shield when someone nearby sneezes. Sneezes are intriguing, because they produce a fluid phenomenon known as vortex rings.

Sneeze Vortex Face Shield

Sneeze vortex: Streamwise velocity distribution along the vertical cross section and the three-dimensional vortex structure. Credit: Fujio Akagi, Isao Haraga, Shin-ichi Inage, and Kozaburo Akiyoshi

“A vortex ring is a donut-shaped vortex that is generated by an instantaneous ejection of fluid from a circular orifice,” said Akagi. “This resembles bubble rings made by dolphins.”

These vortex rings can capture microscopic particles, which sneezing also generates. What happens when a face shield wearer is exposed to a sneeze from an infected person standing 1 meter (39.3 inches) in front of them?

“The vortex rings generated by the sneeze capture the microscopic droplets within the sneeze and transport them to the top and bottom edges of the face shield,” said Akagi, adding that droplets travel to the face shield wearer quickly — within 0.5 to 1 second after the start of the sneeze.

“If this arrival time is synchronized with inhalation, the shield wearer will inhale the droplets,” Akagi said.

The researchers made three findings everyone should know:

First, droplets of sneezes are transported not only by the high-velocity airflow caused by sneezing, but also by the vortex rings generated by sneezing.

Second, microscopic droplets transported by these vortex rings can get inside the shield through its top and bottom edges.

Third, face shields alone are not highly effective in preventing COVID-19 infection.

By gaining a better understanding of face shield weaknesses, researchers believe the protection can be enhanced by reducing the flow getting inside the shield.

“We are currently developing and demonstrating several improved shields,” said Akagi. “We want to contribute to keeping people safe from infection, and believe that one day in the near future, medical workers will be able to prevent infection using only a face shield and a regular mask or, ideally, with only a face shield.”

Reference: “Effect of sneezing on the flow around a face shield” by Fujio Akagi, Isao Haraga, Shin-ichi Inage and Kozaburo Akiyoshi, 8 December 2020, Physics of Fluids.
DOI: 10.1063/5.0031150

6 Comments on "COVID Face Shields No Match for Sneeze Vortex Rings"

  1. Trump: I’m OK with masks. I tell people, wear a mask. But just the other day they came out with a statement that 85% of the people that wear masks catch it
    Dr Fauci masks 60 minutes

  2. What happened to stay 6′ from others? Let’s do this test at that distance and see how it plays out.

  3. Not sure who raised you all, but the Mom that raised me, taught me to sneeze into a tissue or my elbow not AT people from any distance.

  4. Somebody sneezes near me, I move farther away before I take a breath.
    But seriously who ever believed a clear shield was going to stop airborne virus particles, no matter how they got into the air?

  5. I wear a face shield. The thing is…if everyone is wearing a mask or shield, and I’m wearing my shield, they are protected from me and I’m protected from them. That’s why, in these times of Covid 19, I’m asking that EVERYONE wear a mask or shield when in public.
    Thank you.

  6. Which software is being used to make this simulations?

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