A new study finds that masks provide different levels of protection from the coronavirus depending on what they're made of. Professor Sarah Brooks of Texas A&M shot puffs of salty air through different materials and counted how many salt particles came out the other side. Her team found that vacuum bags were good, air filters for AC units were excellent, but coffee filters performed poorly. Worst of all were cotton fabrics, regardless of thread count. Brooks says people who make their own masks should keep these results in mind.
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