In the wake of the COVID-19 pandemic, the U.S. Centers for Disease Control and Prevention recommends that people wear masks in public.
Because N95 and surgical masks are scarce and should be reserved for health care workers, many people are making their own coverings.
SARS-CoV-2, the new coronavirus that causes COVID-19, is thought to spread mainly through respiratory droplets when an infected person coughs, sneezes, speaks or breathes. These droplets form in a wide range of sizes, but the tiniest ones, called aerosols, can easily slip through the openings between certain cloth fibers, leading some people to question whether cloth masks can actually help prevent disease.
One layer of a tightly woven cotton sheet combined with two layers of polyester-spandex chiffon -- a sheer fabric often used in evening gowns -- filtered out the most aerosol particles (80-99%, depending on particle size), with performance close to that of an N95 mask material.
source: American Chemical Society