All depends on the setup. If running a sealed setup then yes definately, in a fairly large area with intake and exhaust it wouldn't be necessary. If running a sealed area you need to supplement CO2 with any lights, that doesn't mean you need to go to extreme levels, 400ppm like outside is fine.
Haha yeah but by sealed we just mean no air intake and no exhaust.
I have no idea about how many spores can be on a person. I try to keep it clean in there, have had a few big colas get the odd bit of Botrytis but nothing major.
Havnt had any bug issues in my sealed room yet besides Gnats and a few ants finding their way in somewhere. Bloody hate gnats.