Nothing to do with coronavirus and masks, this photo was done in jest (obviously), but in retrospect, it does bring up masks’ obvious deficiency (writ large), that is to say the gaps between fibers are on the order of 500 µm (for cloth), whereas aerosolized droplets are about 15 µm. (Corona-virions are <4 µm). So the real question is: (proportionally) can a bowling ball roll through a doorway? Umm, Yes!!
People have this nasty habit of “breathing” (which I admit I’ve gotten very used to, for me it’s almost like breathing). On inhalation, there is a reasonable vacuum that will bring air from the outside in. Watch masks, they move in and out like a diaphragm. If the virions are in the air, in aerosolized droplets, they are well dispersed, thoroughly mixed and will be inhaled masks or no masks.
Masks will work better at blunting the expulsion from an ill-carrier’s sneeze, capturing the multi-million -fold higher density of virions than they will at preventing inhalation. Therefore there greatest efficacy is in covering up the exhalation of the already-ill or -infected rather than in preventing contagion from the not-yet infected — although granted it may be difficult absolutely to know if one is infected or not at any given moment. Facebook