Fresh air

You realy need good air exchange if possible bring air in from outside,but if the grow room is a room bulit in a room then pulling air from the room the grow area is built in will do just has good.What i mean by this is i have a tent grow and my air is pulled in from the room the tent is in.Just make sure that the bedroom or the room yr grow tent is in has the windows open so fresh air can be brought in.I personaly do not like venting air from a room out side this could cause problems with the police,but pulling fresh air in from outside is ok but either ways work.I would on recomend pulling air in from the room the seperate grow area is in if its a big room if its only small then pull air in from outside.....................tyke...................................

An a/c works by blowing air over a coil that has freon in it, as the air passes over, the freon absorbs the heat, you then need to exhaust this heat somewhere. Fresh air is not needed as you can recirculate the same air over and over, the plants don't need oxygen, they need c02. The reason you would want fresh airflow is if your not supplementing c02, then you would get it from a fresh air intake. If your supplementing c02, then you would not need fresh air, but you would lose alot of c02 in your exhaust. This is why I use a sealed room with c02 supplied and a minisplit a/c. No exhaust and no intake. room at 1500ppm always.

i have no intake , no exhaust and my plants are in a closet and fine.

Ya know, I would say I think you are on the right track but no.
If the plants are still that small they are not using that much co2.
Whats the temperature of the root zone? Maybe a seedling heat mat would speed things up. Its winter here.