Some fabrics work better than others. This Wake Forest Research group studied 0.3 micron size particles. Regular surgical masks filtered out 62 percent to 65 percent of particles. For comparison, N95 masks filter 95 percent of those particles. The best masks were constructed of two layers of heavyweight “quilters cotton” with a thread count of at least 180, and had thicker and tighter weave. Some were found to perform even better than the surgical masks. “We had some that performed at 79 percent,” Segal told NBC News. Adding a third layer of flannel sandwiched between two tightly woven layers of high thread count improved performance.
But the fabrics led to a variety of results. One piece of cloth filtered just 1 percent of particles, rendering it virtually useless. Knitted fabrics and fabrics you can see light through did not do well.
Samuel Bowen, MD