How effective are masks? A simple test offers some answers

A doctor and student at the University of South Carolina medical school demonstrated what’s known as a particle blocking test.
Updated: Aug. 27, 2020 at 10:14 AM EDT
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COLUMBIA, S.C. (WIS) - For those wondering how effective masks can be at stopping the spread of COVID 19, this simple test offers a shocking glimpse.

A doctor and student from the University of South Carolina medical school demonstrated what’s known as a particle blocking test.

Dr. Traci Testerman, an Assistant Professor in the Dept. of Pathology, Microbiology and Immunology and Jahnelle Jackson showed WIS how it works.

The test uses three simple ingredients: powder, gauze and a black light.

The powder is made up of fine particles to simulate viral particles.

For the test, Jahnelle sprinkled the powder on top of four layers of gauze, which Testerman says is the typical thickness and porousness of a cloth mask.

Jahnelle then held up the gauze and exhaled a few forceful breaths to simulate talking or singing, forcing the particles through the layers.

When the lights were turned off and the black light was turned on, it became clear how far the particles spread with a typical face covering.

With four layers, most of the particles only landed a few inches away, but some reached a foot or more.

They repeated the test with three layers of gauze, showing the highest concentration of particles were still in close range -- from 6 inches to a foot.

With two layers, the particles traveled 4 to 5 feet. With a single porous layer of gauze, or no gauze at all, the particles could travel anywhere and everywhere within a 6-foot radius.

With nothing to stop the particles, they lingered in the air for 20 to 30 seconds.

“The lighter the particle, the longer they linger” Testerman explained. “You’ve probably seen sunlight go through a dusty room. You see how that just kind of lingers. When you have really light particles, they can linger a long time.”

Still, Testerman says viral particles need to travel a difficult path through the air to infect another person. She says this test shows how a mask makes that path all the more difficult.

“If you wear a mask, you’re really limiting the droplets you’re putting into the air,” she said. “And then for other people wearing a mask, it really reduces the inhalation.”

While not all masks are created equal, experts say an N95 mask might be best. But Testerman says the powder is proof: anything is better than nothing.

“People who are infected in spite of wearing masks tend to have milder cases because they are inhaling fewer viral particles and that gives your immune system more time to fight before that virus ramps up and really starts causing problems,” she said.

For a video tutorial from the Department of Health and Environmental Control on how to make a mask at home, click or tap here.

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