Also, clean rooms are designed to keep dust out of the Fab. They are positive pressure rooms versus a virus lab which would be negative pressure rooms to keep material inside the lab. Similarly with protective suits. I.e. in the Fab they don't care if anything enters the clean suit you are wearing - just that nothing leaves it. In a virus lab it would be a positive pressure suit.
Is that an important distinction though? In a clean room, there shouldn't be viral particles in the room so the suit wearer would be equally safe if their suit was positive or negative pressure (so long as everyone else has their suits the same way).
