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Researcher says material, fit key to effective masks


MADISON (WKOW) - In one trial at UW-Madison, researchers found effective mask use in a group can reduce particle transmission by more than 200 percent.

Scott Sanders is an engineering professor at UW-Madison, but he's been researching mask efficacy since the start of the pandemic.

He says disposable surgical-style masks are the most effective because they're made of a filtering material.

"When I'm breathing out, my aerosol gets collected there and when I'm breathing in, whatever aerosol is in the room also gets collected, so it's protecting both directions," he said Tuesday.

Sanders said well-fitting cloth masks are also good options, but they aren't as good at protecting the wearer from breathing in outside particles.

"Even just from breathing, you're releasing smaller aerosol droplets that just go wherever the air goes," Sanders said. "It's harder to protect from those smaller droplets. Even four layers of tightly-woven cotton won't catch most of that."

Sanders said a team of UW-Madison researchers set up a mock classroom with 17 mannequins to test how much masks reduce the spread of aerosolized particles.

He said in the experiment, when the infected mannequin wore a well-fitting mask, 1/15 the amount of droplets were released into the room compared to when the mannequin was not wearing a mask.

When the non-infected mannequins also wore well-fitting masks, they were exposed to 1/15 the amount of particles, too.

Sanders said this represented a 225-time improvement compared to when no mannequins were wearing masks.

"When everyone's wearing masks properly, it's actually quite safe to be in those environments," Sanders said. However, he noted it's usually quite hard to ensure everyone in a space is wearing a fitted mask that does not allow air and virus particles to escape out the sides or top.

Sanders said though masks help reduce the spread of COVID-19, they are not perfect, and they are not substitutes for physical distancing.

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