Use either passive (vent hole in the bottom) or active where you force air in.

Passive will allow odor to escape out active will not.

Either way fresh air in moving across the plant is a good thing. Make sure you monitor the temperature at the top of the canopy 24/7 from outside the room so you have real world data.
Zandor Reviewed by Zandor on . what ventilation system should i be looking for? O'k guys I have a few question concerning my grow room,I was wondering what I could use to dump the heat in the room and at the same time draw fresh air back into the grow room......here is my set up... The room is 9ft long 5ft wide and 8ft high my grow table that I have my plants on is about 5ftx4ft under a 1000w hps I am into my 3rd week of flowering and boy is the room getting hot! alot hotter then I anticipated!,I keep opening up the door to the grow room and at most times I leave Rating: 5