If you haven't been double masking, now's probably the time to start: We know at least the UK variant, which is more transmissible than other variants, is spreading rapidly. But there's a right way and a wrong way to do it: https://qz.com/1969361/how-to-double-your-mask-effectively/ 1/x

2/x First, the basics: Double masking is just wearing one mask over another. The benefit is that you'd have an extra layer of filtration to stop your droplets flying out, and to stop others' reaching your own respiratory system.

3/x @CDCDirector is studying how well double-making works, but a lot of folks, including Dr. Anthony Fauci, have said "it just makes sense" and have started doing it—I have too! I use a KN95 with a construction mask over it (like a surgical mask, non medical grade)

4/x More filtration is great, until you get to the problem of breathability. If your 2 masks are so thick that there's actually no airflow between them, you'll end up breathing through gaps in the sides; this effectively means you (+ others) have got...0 protection

5/x @CDmasterZang over at @NIST is studying this issue; he told me that gaps are often at the back of your cheeks, or over the bridge of your nose. Droplets coming through that gap look "like a geyser" he told me.

6/x There aren't standards for how to double mask yet, and which masks to include because...there aren't standards for masks yet. It normally takes YEARS to standardize something used commercially—ASTM International is working on them now for later this year.

7/x One way to see how much unfiltered air is seeping out of your masks is to go outside and breath while wearing glasses (or sunglasses). How fast do they fog up? You want the least amount of fog possible. If you're getting a ton, perhaps your mask too thick (or misplaced).

8/8 It's worth thinking about and exploring how you can double up with your masks comfortably and effectively—doing so is going to be really important in the coming weeks. https://qz.com/1969361/how-to-double-your-mask-effectively/