Thread by @DearPandemic

1/ Q: If masks work, why can I still smell farts when I'm wearing one?
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A: We know there are lots of folks out there who have similar concerns about masks. Maybe you've wondered about how useful/safe masks are. We at DP are here to help fight the #infodemic, so let's dive in!

2/ Why can I still smell things through a mask?

Well, masks aren't actually supposed to block all air flow (which actually gets at another misunderstanding about masks -- that they are dangerous because they interfere with breathing).

3/ Masks instead block droplets containing COVID -- they do also offer the mask wearer some protection from others as well. It turns out that the smell from a fart is caused by methanthiol & other similar sulfur containing molecules, & these molecules are TINY.

4/ Check out the lifehacker piece for some numbers, but coronavirus is up to 34,000% larger than fart molecules! Think about the approximate comparison between a basketball & a poppy seed!
vitals.lifehacker.com/why-you-can-sm…

5/ This means that the virus particles have a much harder time getting through a mask than odors in the air. That is not to say that masks protect 100% -- unfortunately almost nothing in life is 100% -- but they do offer a lot of protection.

6/ As far as oxygen & CO2, they are also both much smaller than the virus, so that is why they can pass through (& it is safe to wear a mask all day). ⁠⁠😷

7/ BOTTOM LINE: Masks block things that are bigger, & allow things that are smaller to pass through. Luckily for us, air & CO2 are small (unfortunately, fart molecules are also small) & coronavirus is big.

8/ Many of the conspiracy theories about masks are contradictory -- masks are both useless because the virus can pass through AND dangerous because oxygen and CO2 cannot. It's actually the opposite -- they work because they block virus while also, thankfully, allowing airflow.