Yeah that's fair -- there might be some high-exposure situations (like being coughed on) where infection is very likely with or without a face shield.

I suspect that a lot of airbone infections are from inhaling small doses here and there though, considering how long mucus droplets can stay suspended [1] --

> Particles of diameters 1-3 μm remained suspended almost indefinitely, 10 μm took 17 min, 20 μm took 4 min, and 100 μm took 10 s to fall to the floor.

[1] https://www.mintie.com/assets/img/education/Aerosol%20transm...