Name:   MartiniMan - Subject:   That is my understanding Date:   7/7/2020 4:14:51 PM

When you inhale you bring the smaller droplets (what we call aerosols) through the mask and around the edges and inhale them and vice versa when you exhale.  That's why we have to do fit testing with an irritant smoke to confirm that there are no gaps on the edges of the full face respirator and that the cartridges are the right design to eliminate the chemical or biological hazards you expect to encounter.  Most the air that people exhale wearing the cloth masks actually escape around the edges and most of the air they breath likewise comes from the open edges, even if they feel the mask being sucked into their mouth when they inhale.  Much worse around the edges when you exhale because your breath pushes the mask away from the face and widens the edge openings. 

The masks do help with larger droplets when you cough or sneeze but those don't carry very far anyway.  It's the aerosols that stay suspended in the air in the breathing zone that are most problematic and those are smaller than the cloth (think screen door on a submarine) so they pretty much go right through.  Granted they also carry less virus mass but again, the droplets tend to fall to the ground fairly quickly anyway.