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A chilling video shows how droplets from a dummy’s cough can spread a dozen feet — double the distance people are encouraged to stay away from each other under social-distancing recommendations — but wearing a mask can drastically limit the spray.

Two engineering professors at Florida Atlantic University performed the eye-opening experiment by filling a dummy’s mouth with a mixture of water and glycerin to create a germ-like spray, according to CNN.

They then used a pump to make the mannequin cough and measured how far the droplets traveled using LED and laser lights.

“It generates particles on the order of 10-20 microns, which is roughly close to what the smallest droplet sizes are when we cough,” said Sid Verma, an assistant professor of engineering at FAU.

Almost instantly, the droplets traveled three feet. Within 12 seconds, they were at six feet. In about 41 seconds, the droplets were at nine feet — three feet beyond the recommended guidelines, he said.

“It’s already reaching roughly nine feet now, still moving farther, slowly,” Verma said as the fog of droplets kept moving forward. “It’s getting closer to 12 feet now.”

Manhar Dhanak, chairman of the school’s Engineering Department, said the droplets could linger at a nine-foot distance for two to three minutes — becoming less dense the farther they travel but still able to carry the disease.

When the professors put a mask on the dummy, particles dispersed from its sides — but did not travel far.

“We found that wearing a face mask doesn’t stop the particles 100 percent, but it does slow down the cough jets,” said Dhanak, adding that keeping a distance of at least six feet is important.

“Six feet is the minimum distance that you should keep,” Dhanak said. “Further is better.”

Stella Batalama, dean of FAU’s College of Engineering and Computer Science, said: “Initial results from the experiment that professors Dhanak and Verma conducted have important implications for how we protect the public from this highly infectious disease.

“There is currently a gap in knowledge over how COVID-19 spreads as well as a scientific debate about how the disease moves in the air. This experiment will help to shed more light on the spread of the disease through aerosols.

“Moreover, it underscores why it is so essential to cover your cough and sneezes and to wear a face mask when you are out in public settings,” she said.