During the wake of the COVID-19 Pandemic the CDC recommends people wear face masks in public. Due to the shortage of N95 and surgical masks, they have recommended people make their own coverings. Some materials can filter out particles much better than others, significantly affecting how well a homemade face mask may protect a person from the virus.
The COVID-19 virus is thought to spread mainly through respiratory droplets when an infected person speaks, breathes, coughs or sneezes. The droplets form in a wide range of sizes, however the tiniest ones called aerosols can easily slip through the openings between a variety of cloth fibers. This has lead to some people questioning as to whether cloth masks can actually help prevent disease.
Supratik Guha at the University of Chicago and colleagues set out to study the ability of common fabrics alone or in combination to filter out aerosols similar in size to respiratory droplets.
The team used an aerosol mixing chamber to produce particles that range from 10nm to 6um in diameter. A fan was used to blow the aerosol across a variety of cloth samples at an airflow rate similar to a person’s respiration at rest. The team then measured the size and number of particles in air before and following passing through the fabrics.
One layer of tightly woven cloth along with two layers of polyester-spandex chiffon which is a sheet 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.
They then substituted natural silk or flannel or simply using cotton quilt with cotton-polyester batting which produced similar results. The team has pointed out that tightly woven fabrics such as cotton can act as a mechanical barrier to particles. Fabrics that hold a static charge such as chiffon and natural silk serve as an electrostatic barrier.
Researchers are reporting that a combination of cotton with either natural silk or chiffon can effectively filter out aerosol particles if the fit is good. You can also use doubled up 600 thread count pillowcases or flannel pajamas or cotton T-shirts which will make a mask that will provide up to 60% filtration. Other materials that can be used to filter our dangerous particles include vacuum cleaner bags, HEPA filters, and quilter’s cotton. You do want to be careful of materials like household air filters that many contain fiberglass which can damage the lungs even if they filter out particles.
To view the original scientific study click below