Homemade Mask with Evening Gown Fabric Is As Good As N95 Mask?
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 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.
Therefore, Supratik Guha at the University of Chicago and colleagues wanted to study the ability of common fabrics, along or in combination, to filter out aerosols similar in size to respiratory droplets.
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The researchers used an aerosol mixing chamber to produce particles ranging from 10nm to 6 μm in diameter. A fan blew the aerosol across various cloth samples at an airflow rate corresponding to a person’s respiratory at rest, and the team measured the number and size of particles in air before and after passing through the fabric.
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.
Substituting the chiffon with natural silk or flannel, or simply using a cotton quilt with cotton-polyester batting, produced similar results.
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The researchers point out that tightly woven fabrics, such as cotton, can act as a mechanical barrier to particles, whereas fabrics that hold a static charge, like certain types of chiffon and natural silk, serve as an electrostatic barrier.
However, a 1% gap reduced the filtering efficiency of all masks by half or more, emphasising the importance of properly fitted masks.
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CITATION
American Chemical Society. “The best material for homemade face masks may be a combination of two fabrics.” ScienceDaily. ScienceDaily, 24 April 2020. <www.sciencedaily.com/releases/2020/04/200424081648.htm>.
