Keep your distance. Although wearing a mask can limit transmission of droplets that spread COVID-19, it may not be enough unless people also stay at least six feet apart, new research shows.

Researchers at New Mexico State University in Las Cruces found that at distances of less than six feet, enough droplets to potentially cause illness still made it through several masks made of commonly used materials.

“A mask definitely helps, but if the people are very close to each other, there is still a chance of spreading or contracting the virus,” said study co-author Krishna Kota, an associate professor of mechanical and aerospace engineering. “It’s not just masks that will help. It’s both the masks and distancing.”

For the study, the researchers built a machine that used an air generator to mimic human coughs and sneezes. The generator was used to blow tiny liquid particles through laser sheets in an airtight tube with a camera. The liquid particles are like the airborne droplets of sneezes and coughs.

The investigators tested how five types of mask materials affected the spread of droplets. They tested a regular cloth mask; a two-layer cloth mask; a wet, two-layer cloth mask; a surgical mask; and a medical-grade N-95 mask.

Each captured most of the droplets. The N-95 mask statistically blocked 100% of droplets, while the cloth masks allowed 3.6% of droplets through.

At distances of less than six feet, those small percentages can be enough for someone to spread their illness. That’s especially true if someone with COVID-19 sneezes or coughs several times, the researchers said. A single sneeze can carry up to 200 million tiny virus particles.

“Without a face mask, it is almost certain that many foreign droplets will transfer to the susceptible person,” Kota said in a news release from the American Institute of Physics.

“Wearing a mask will offer substantial, but not complete, protection to a susceptible person by decreasing the number of foreign airborne sneeze and cough droplets that would otherwise enter the person without the mask. Consideration must be given to minimize or avoid close face-to-face or frontal human interactions, if possible,” he advised.

The study did not account for leakage from masks, whether worn properly or improperly, which can add to the number of droplets released into the air.

The findings were published online Dec. 22 in the journal Physics of Fluids.

More information

The U.S. Centers for Disease Control and Prevention has more on social distancing.

SOURCE: American Institute of Physics, news release, Dec. 22, 2020

Cara Murez

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