I'm back. Sorry, had to do some shit today. So are you going to put a carbon filter in the tent, then pull air through that, through the cool tube, and out for the light? If so, you'll need a 6" inline fan to pull that, and you're definatly going to need the filter, for sure. Second, you can open the lower flaps which will give you passive intake, which is fine, but this lets out light, and lets in light, which sucks. The better option is to go with another inline to push fresh air in, or, get a $50 inline vent booster fan from Homedepot or whatever which will provide a constant source of fresh air. The only issue is that air out will be more than air in, and could get a negative pressure situation. I'm just now setting up a new space, a 4x8 tent, and am going to do just this.