if you are needing a mask,just d a little research as to what is acceptabel,what (as recommended ) has 3 ply,and the like..there are many differing kinds without the "vent"..
So no masks that have an exhaust valve at all? And American comes up with another not thought out idea. Hey, CDC and American Airlines..there are masks out there, with exhaust valves, that have filtration systems built in. Didn't think of that 1 with the blanket statement: "Not allowed: Face coverings with exhaust valves." did you.
The cheap masks dont fo anything but allow breath to openly be expelled.. but I get it..