Dr. Scott Segal, chairman of anesthesiology at Wake Forest Baptist Health, led a study which concluded that quilters tend to use high-quality, high-fabric count cotton. He found that best homemade masks were as good as surgical masks or slightly better, testing in the range of 70 to 79 percent filtration. Homemade masks that used flimsier fabric tested as low as 1 percent filtration, Dr. Segal said. The top designs were masks constructed of two layers of high-quality, heavyweight “quilter’s cotton,” a two-layer mask made with thick batik fabric, and a double-layer mask with an inner layer of flannel and outer layer of cotton.
Most scientists who conducted the tests used a standard of 0.3 microns because that is the measure used by the National Institute for Occupational Safety and Health for medical masks.
Linsey Marr, a Virginia Tech aerosol scientist an expert in the transmission of viruses, said the certification method for respirators and HEPA filters focuses on 0.3 microns because particles around that size are the hardest to catch.
“Even though coronavirus is around 0.1 microns, it floats around in a wide range of sizes, from around 0.2 to several hundred microns, because people shed the virus in respiratory fluid droplets that also contain lots of salts and proteins and other things,” said Dr. Marr. “Even if the water in the droplets fully evaporates, there’s still a lot of salt and proteins and other gunk that stays behind as solid or gel-like material. I think 0.3 microns is still useful for guidance because of the minimum filtration efficiency … and it’s what NIOSH uses.”
Some say the best material to use is tight-weave cotton and that synthetic or polyester doesn’t work because of the virus’s ability to survive on those. A scarf doesn’t fit close enough on your face and so a mask is better.
Scarfs do not do as well as a mask as they fit closely to your face.