With N95 and surgical masks left for medical professionals and the CDC advising widespread mask usage for the general population, a new category has emerged for fabric masks designed for everyday wear. This brings into question the best type of face mask material. The CDC posted a no-sew mask pattern using a bandana and coffee filter, and posted videos on using rubber bands and folded materials commonly found at home. These kinds of masks limit the spread of the wearer's own germs, in the chance they are infected but asymptomatic. But for protecting against incoming germs, material and fit is important.
Homemade masks made of high quality, high thread count cotton have proven to be almost as effective as professionally manufactured surgical masks, with a range of 70 to 79 percent filtration. There’s also a trick to see how effective fabric masks are. “Hold it up to a bright light,” Dr. Scott Segal, chairman of anesthesiology at Wake Forest Baptist Health who recently studied homemade masks, told the New York Times. “If light passes really easily through the fibers and you can almost see the fibers, it’s not a good fabric. If it’s a denser weave of thicker material and light doesn’t pass through it as much, that’s the material you want to use.” Again, it’s important to note that the common person going to the pharmacy for the ever-elusive roll of toilet paper or to restock on groceries likely does not need the medical grade protection of an N95 mask if they are not coming into direct contact with someone infected with COVID-19, but precautions are still necessary. The challenge for a lot of people and companies making masks is finding something that has high filtration ability but is still breathable. “You need something that is efficient for removing particles, but you also need to breathe,” Dr. Yang Wang, an assistant professor of environmental engineering at Missouri University of Science and Technology and award-winning aerosol researcher, told the New York Times. In the context of reserving N95 masks for frontline health care professionals, Dr. Wang’s research looked at allergy-reducing HVAC filters, which captured 89 percent of particles with one layer and 94 percent with two layers. Furnace filters captured 75 percent with two layers, and 95 percent with six layers. Cotton—especially tight-weave varieties—has been, for the most part, very effective, which makes it even more heartening to see apparel companies spring into action. Dr. Wang’s study also found that the best homemade mask designs were made with two layers of high-quality, heavyweight “quilter’s cotton,” a double-layered mask with batik fabric, and a double-layered mask with an inner flannel layer and outer cotton layer.
Masks made with high quality cotton can protect against a high percentage of contaminants. While some infectious disease experts advise against synthetic or polyester fibers for masks, as studies show the virus survives longer on these fabrics, non-medical masks should be washed after each use anyway, reducing the risk.