Smoke or airborne disease?
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Corsi–Rosenthal Box - Wikipedia
https://en.wikipedia.org/wiki/Corsi%E2%80%93Rosenthal_Box
A cheap, fast and effective way to help your community breathe better. Most effective indoors. Pair with an N95s if you plan on protesting with your friends during a pandemic but P100s with a filter for organic vapors to protect against tear gas [try to contain tear gas as quickly as possible as cleanup is much harder].