Yup, Think about what you're doing before you do it. I bought some N95 face masks on an impulse because they claimed to remove 95% of all particles at .30 microns or larger. It wasn't until later that I did my 'homework' and found out that most viruses are .15 microns or smaller. Live and learn.
I think the Japanese experience with face masks is that they prevent the wearer from blowing his spores all over kingdom come.
If you are in a supermarket etc and everyone is masked, everyone is safer....from each other.