Fab room ceiling height?

My question is how big your fab room is going to be and how are you going to ventilate it. Metal working generates smoke and sometimes quite a bit. Taller is better.
My fab room will be 12x20.
For ventilation, I could put a few exhaust fans in the ceiling, and ideally, I’d like to have one of those movable vent hood things to use over the welding table then to suck the smoke out before it house time to