The Best and Worst Materials for Face MasksIvy Gutierrez
At the start of the pandemic, we were told not to wear masks because there was a legitimate concern that the limited supply of surgical masks and N95 respirators should be saved for the health care workers. UC San Francisco epidemiologist George Rutherford, MD, believes it was a mistake to tell the public not to use masks. “We should have told people to wear cloth masks right off the bat,” he said.
Once the scientists started gathering more knowledge on the virus, CDC changed its guidance and now strongly advocates mask wearing for everyone. Research shows that both pre-symptomatic and asymptomatic transmission is not only possible, but very common. Monica Gandhi, an infectious diseases physician and researcher at the University of California, San Francisco, explains that studies vary, but “evidence from 16 studies and estimated the overall rate of asymptomatic infection [seem] to be 40%-45%“.
Scientists think people infected with the coronavirus (SARS-CoV-2) are most contagious from a few days before COVID-19 symptoms appear till a few days after they start. By the time we receive your positive diagnosis (if you exhibit symptoms and go get tested, or just get randomly tested), our peak for spreading COVID-19 has already passed.
Armed with all this new knowledge and the desire to stop the spread of the virus and protect ourselves, one may find itself looking at different kinds of masks available and wondering – what’s the difference?
As it turns out, there is quite a bit of difference between different kinds of masks. Researchers at Duke University tested the effectiveness of 14 commonly available masks and found that surgical masks and N95 respirators without valves worked the best at blocking respiratory droplets from projecting into the air when a person talks. A variety of double-layer polypropylene and cotton masks also reduced a significant amount of spray from normal speech.
Least effective, however, were bandanas, knitted masks and neck fleeces (also called gaiter masks), the latter of which may be worse than wearing no mask at all. The researchers found that neck fleeces actually dispersed more spray into the air, not less, because the material broke down larger respiratory droplets into smaller particles.
If you are making your own mask, consider using synthetic material polypropylene, laid in between two layers of cotton. This combination seemed the best for home made masks. After this three-layer combo, a double layer of polypropylene was a slightly worse choice, but still quite good.
Several layers of cotton masks were even more effective in containing respiratory droplets than N95 masks with exhalation valves. The reason is suspected to be the fact that these masks are made to protect the user from breathing in harmful materials, not necessarily the other way around.