Katie Notopoulos over at Buzz Feed’s How to Plague advice column on when you should wear your mask:

A good way to gauge the amount of distance where it’s OK to dangle your mask around your neck or off one ear is to imagine your mouth is your asshole. If you were completely alone, it would be fine to let your nude tushy hang out, but you’d want to pull on your pants as soon as you saw anyone coming, even from 100 feet away. Basically, if someone can see you, mask up.