They used to post graphics that basically said masks only work if you and the infectious person are both wearing masks. In other words, if only the uninfected p

They used to post graphics that basically said masks only work if you and the infectious person are both wearing masks. In other words, if only the uninfected person is wearing a mask, or if only the infected person is wearing a mask, all bets are off. Basically they all demonstrated that you need a mask to keep some of the infectious stuff out of the air, and another mask to avoid as much breathing in what the infected person's mask didn't filter. I imagine that has not changed. It's hard to tell though because none of the subsequent tests seem to ever take that into account.