“Oh I see....germs can’t get out of the mask but can only come through”
Bonemaker,
The only foolproof way would be to be breathing air from a closed-loop breathing system.
Can you assure, with a flimsy, paper face mask that as one breathes, no outside air would not penetrate the sides of the mask? No, you cannot!
My point was that no one should consider that a face mask would be foolproof and would protect against all possibilities.
Also, if you decide to respond then please tone down the sarcasm. It only makes you look like a sarcastic, smart ass! ;-)
I am... 
Seriously, unless the mask is absolutley air tight and the pores are smaller than the virus then there is going to be a two way flow of stuff. But it seems odd doesn't it that everyone in the medical field is screaming for an endless supply of them.