Ideal scenario would be most of the smoke gets pushed down in a knee-wards direction, which is well within the realm of the imaginable.
You ARE the person in the faceshield (I assume you meant that instead of facemask), you don't control what other people do so assume they uncovered. The smoke is in the air, it can reach you. Will it get around that shield or not?
This is all about containing the spread.
Although I suppose in hindsight that explains why people were downvoting me.
If your plan is to only block most of the virus then perhaps you should rethink it.
It's like stating that a hole in the hull is not a problem because the rest of the ship keeps most of the water out.
This is thought to be why an unexpectedly high proportion of young, healthy doctors and nurses are getting seriously ill from Covid-19. Statically, you'd expect almost all of them to get mild disease.