Months into the coronavirus pandemic, face masks remain a key tool for controlling the spread of COVID-19 — and, according to a recent update from the Centers for Disease Control and Prevention (CDC), research shows that cloth face masks protect both wearers and those around them from coronavirus infection.
But with so many store-bought and DIY options now available in a variety of styles and fabrics, how can you know your mask is working as well as it should?
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According to the CDC, the most effective cloth mask fabrics are tightly woven, like cotton and cotton blends, two or three layers, and breathable.
Airborne disease transmission expert Linsey Marr, a professor of civil and environmental engineering at Virginia Tech, also looked at the question of mask materials in a study published Nov. 20 on the preprint server medRxiv.
The study, which has not yet been peer-reviewed (Marr and her team are awaiting publication in a scientific journal), tested nine homemade masks and their materials, as well as a surgical mask and a face shield, to see how well they filtered tiny particles and how well they protected the wearer and those around them.
Based on their findings, the researchers recommend a three-layer mask, where two outer layers made from a tightly woven cotton material sandwich a filter layer.
But for those who already have a collection of favorite masks at home, here’s how Marr says to ensure you’re getting the most out of your current selection:
Choosing the right fit
“Fit is really important, because if there are any leaks … your mask isn’t doing its job,” Marr says. The CDC recommends a mask that fits snugly around the nose and chin, with no large gaps around the sides of the face.
To that end, Marr recommends looking for masks with a nose wire, which can be shaped to conform to the bridge of your noise, and considering masks that have ties instead of ear loops, since they can be positioned on the head for a custom fit (also a good alternative for people who find that ear loops cause soreness).
Fit is also the main reason face shields shouldn’t be worn alone as a substitute for a cloth mask, Marr says, since the large gaps along the sides of the shield allow for unrestricted airflow.
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Fabric and filter options
Marr and her team found that commonly available materials like the thin, tightly woven cotton you might find in a blouse performed well in the study, especially when used as the two outer layers in their recommended three-ply mask with a middle filter layer (the filters they tested included DIY options like vacuum bags and coffee filters).
Some cloth face masks come with an inner filter layer already included, or have a pocket into which one can be inserted. If you don’t have a mask with a filter or don’t want to embark on a DIY project to add one, Marr recommends a simple alternative: simply wear a surgical mask under a well-fitting cloth mask for added protection.
Avoiding common mask mistakes
Even the best mask won’t work well if worn incorrectly. Marr says common mask-wearing errors include leaving your nose outside of the mask and pulling your mask down to talk to someone. “That’s when you most need the mask,” she says, “in terms of protecting others.”
Other mask don’ts, according to the CDC, include using single-layer cloth masks, masks with exhalation valves or vents, and masks made from either loosely woven fabric or materials that are hard to breath through, like plastic and leather.