Photo credit: Edward Jenner/Pexels.com

Date: 6 July 2020

Institution: University of Wisconsin–Madison

Digest: Researcher simulated cough to visualize the risk of the spread of virus particles by the escaped droplets from cough using masks of varying styles and materials, using his combustion systems research tool.


In his video, Sanders used a mannequin to produce a simulated cough (adding more droplets than are in an actual cough, to make the cough easier to see). While the visualization doesn’t directly track the spread of virus particles, Sanders believes it will help people see a risk that is otherwise invisible.

With no mask, droplets travel more than 3 feet in front of the mannequin. Masks with valves allow many particles to escape. Cloth masks do a better job of containing the particles; however, cloth masks with a loose weave don’t perform as well as those made with tightly woven cloth. And, masks without fitted nose pieces allow particles to escape through gaps in the top, under the wearer’s eyes. Other mask styles, including flat-fold masks, can leak particles out the sides near the ears.

UW–Madison Professor Scott Sanders’ team modified a mannequin so that the mouth releases a puff of air containing fog. The air speed is similar to a real human cough, but there is much more fog than an actual cough. This condensed video looks at how well masks contain the fog, using regular lighting and laser lighting, and shows results from testing different mask styles.  Video credit: Scott Sanders

Sanders found that, in general, the homemade mask shape most effective at containing droplets is a neck-gaiter-style mask that combines a nose piece with an elastic cord that wearers can toggle to snug the mask to their face. The extra effectiveness of the neck-gaiter mask does come at a cost: It is a larger mask, and it isn’t as easily removed.

“That said, wearers can quickly and easily slide the gaiter down around their neck and back up to their face as needed,” he says.

Additionally, the neck-gaiter mask can be a good alternative for small children or others for whom traditional masks might be difficult to fit, and it may be more tolerable for people who are sensitive to wearing other mask styles because of underlying respiratory or other concerns.

Sanders believes his visualization enables people to see a risk that is otherwise mostly invisible.

“I hope that research like this will enable people to make informed decisions about distancing and mask-wearing,” he says.

He also has created a video that shows a simple way to sew the neck-gaiter mask using a rectangle of tightly woven fabric, a toggle, cord and metal nose piece.

“There are two aspects to masks: Personal protection, or reducing the amount of airborne droplets the wearer inhales, and source control, which is containing the wearer’s own respiratory droplets,” Sanders says. “The ideal mask would do an excellent job at both aspects, and work whether wearers are talking, yelling, coughing or sneezing. That is a tall order — even for medical-grade respirators, let alone homemade masks. However, as the video shows, a homemade cloth mask with a nose piece can provide significant source control, which in turn could improve public health.”

Sanders emphasizes that home-sewn masks aren’t designed to replace medical-grade personal protective equipment, and should be used in conjunction with other recommended measures, including physical distancing and frequent hand-washing, among others.

Sanders received funding to conduct this research and produce the videos through the Wisconsin Partnership Program in the UW School of Medicine and Public Health. He is part of a larger team of collaborators within the UW–Madison College of Engineering and across campus that is focused on masks and mask material screening.

Original written by: Renee Meiller

Source: University of Wisconsin–Madison

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