The Centers for Disease Control and Prevention recommends multi-layer cloth masks for the general public. The ideal mask blocks both large respiratory droplets from coughs or sneezes — the primary method by which people pass the virus to others — along with smaller airborne particles called aerosols, which are produced when people talk or exhale.
It should be sealed around the nose and mouth, since any gaps, holes, or vents could allow droplets to leak out and infect another person.
Assuming masks are worn properly, certain materials consistently perform better than others in studies. Based on current research, here’s a ranking of the best and worst face coverings:
In addition to protecting those around you, masks can also offer protection for the wearer, according to the CDC’s recent guidelines.
‘Hybrid’ masks are among the safest homemade options
As a general rule, mask fabrics should be woven as tightly as possible. Fabrics with higher thread counts are better at filtering particles.
It’s also preferable to have more than one layer. The World Health Organization recommends that fabric masks have three layers: an inner layer that absorbs, a middle layer that filters, and an outer layer made from a nonabsorbent material like polyester.
N95 masks are the most protective because they seal tightly around the nose and mouth so that few viral particles seep in or out. They also contain tangled fibers to filter airborne pathogens — the name refers to their minimum 95% efficiency at filtering aerosols. A Duke study showed that less than 0.1% of droplets were transmitted through an N95 mask while the wearer was speaking.
That’s why they’re generally reserved for healthcare workers. But the Food and Drug Administration has also approved some KN95 and FFP2 masks made in China and Europe that offer comparable protection.
Disposable surgical masks are also made of non-woven fabric. A 2013 study found that surgical masks were about three times as effective at blocking influenza aerosols as homemade face masks. (That was true, at least, when air flow was slower than a cough but faster than a human breathing during light work.)
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