MONDAY, Nov. 2, 2020 (HealthDay News)

While most of the billions of face masks people are wearing around the world do their job of preventing the spread of COVID-19, so types performs better than others, new research shows.

A test of all types of face masks found that most fabrics used for non-clinical face coverings effectively filter ultrafine particles.

N95 masks were highly effective, though a reusable HEPA vacuum bag was actually better in some respects, according to researchers from Northwestern University and the University of Cambridge.

They also found that homemade masks made of multiple fabric layers were effective, and those with interfacing (a fabric normally used to stiffen collars) performed well. This improvement in performance, however, makes them more difficult to breathe through than an N95 mask.

“Fabric masks have become a new necessity for many of us since the start of the COVID-19 pandemic,” said study first author Eugenia O’Kelly, of the Engineering Design Center at Cambridge’s Department of Engineering.

Researchers studied the performance of different fabrics when damp and after they had been laundered.

While they found that fabrics worked well while damp and worked sufficiently after one laundry cycle, researchers warned that masks should not be reused indefinitely.

For the study, O’Kelly’s team built a device consisting of sections of tubing, with a fabric sample in the middle. Aerosolized particles were pushed through one end of it, and levels were measured before and after they passed through the fabric at a speed similar to coughing.

Researchers also tested how easy it was to breathe through each fabric.

“A mask which blocks particles really well but restricts your breathing isn’t an effective mask,” O’Kelly said. “Denim, for example, was quite effective at blocking particles, but it’s difficult to breathe through, so it’s probably not a good idea to make a mask out of an old pair of jeans. N95 masks are much easier to breathe through than any fabric combinations with similar levels of filtration.”

It’s a matter of finding the right balance, she said.

“We want the materials to be effective at filtering particles, but we also need to know they don’t put users at risk of inhaling fibers or lint, which can be harmful,” O’Kelly added.

The findings were published online Oct. 29 in the journal BMJ Open.

More information

To learn more about COVID-19, visit the U.S. Centers for Disease Control and Prevention.

SOURCE: University of Cambridge, news release, Oct. 29, 2020

Steven Reinberg

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