Home Lifestyle Health Inexpensive, Visual Proof That Masks Block Droplets

Inexpensive, Visual Proof That Masks Block Droplets

Duke physician Eric Westman was one of the first champions of masking as a means to curtail the spread of COVID-19, working with a local non-profit to provide free masks to at-risk and under-served populations in the greater Durham community.

But he needed to know whether the virus-blocking claims mask suppliers made were true, to assure he wasn’t providing ineffective masks that spread viruses along with false security. So he turned to colleagues in the Duke Department of Physics: Could someone test various masks for him?

Hand-made cotton face coverings provided good coverage, eliminating a substantial amount of the spray from normal speech. On the other hand, bandanas and neck fleeces such as balaclavas didn’t block the droplets much at all. (Image: via pixabay / CC0 1.0)
Hand-made cotton face coverings provided good coverage, eliminating a substantial amount of the spray from normal speech. On the other hand, bandanas and neck fleeces such as balaclavas didn’t block the droplets much at all. (Image: via pixabay / CC0 1.0)

Martin Fischer, Ph.D., a chemist and physicist, stepped up. As director of the Advanced Light Imaging and Spectroscopy facility, he normally focuses on exploring new optical contrast mechanisms for molecular imaging, but for this task, he MacGyvered a relatively inexpensive apparatus from common lab materials that can easily be purchased online. The setup consisted of a box, a laser, a lens, and a cell phone camera.

In a proof-of-concept study appearing online in the journal Science Advances, Fischer, Westman, and colleagues report that the simple, low-cost technique provided visual proof that face masks are effective in reducing droplet emissions during normal wear. Fischer said:

Notably, the researchers report, the best face coverings were N95 masks without valves – the hospital-grade coverings that are used by front-line health care workers. Surgical or polypropylene masks also performed well.

But handmade cotton face coverings provided good coverage, eliminating a substantial amount of the spray from normal speech. On the other hand, bandanas and neck fleeces such as balaclavas didn’t block the droplets much at all. Fischer said:

Westman added that:

Westman and Fischer said it’s important that businesses supplying masks to the public and employees have good information about the products they’re providing to assure the best protection possible. Fischer said:

“We wanted to develop a simple, low-cost method that we could share with others in the community to encourage the testing of materials, masks prototypes, and fittings. The parts for the test apparatus are accessible and easy to assemble, and we’ve shown that they can provide helpful information about the effectiveness of masking.”

Westman said he put the information immediately to use:

“We were trying to make a decision on what type of face covering to purchase in volume, and little information was available on these new materials that were being used.”

The masks that he was about to purchase for the “Cover Durham” initiative? Westman said:

“They were no good. The notion that ‘anything is better than nothing’ didn’t hold true.”

Provided by: Duke University Medical Center [Note: Materials may be edited for content and length.]

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  • Troy was born and raised in Australia and has always wanted to know why and how things work, which led him to his love for science. He is a professional photographer and enjoys taking pictures of Australia's beautiful landscapes. He is also a professional storm chaser where he currently lives in Hervey Bay, Australia.

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