I would suggest mounting your 6" exhaust fan in the roof of the box, sucking air out from there and then thru your charcoal filter.

I had a very similar (almost identical except 4' tall) box that was vented with one of those real cheesy 4" inline fans and the temps stayed fine.
Good luck

PC :smokin:
PharmaCan Reviewed by PharmaCan on . I'm lost...Help...CFL Grow Ok hereā??s the thing I have a 2ft X 2ft X3ft box (1/4inch plywood with 1inch X 2inch framing) raised off the ground 2.5 inches. I have 8 cfls in it 4 are 5000k (hanging in the middle in an X pattern) and 4 are 6500(one hanging in each corner). I have an exhaust fan (6inch fan max cfm 240) it was sucking from the ground threw a 4inch dryer hose(kinda squashed to fit under the box) which I thought was decreasing the performance of the fan) so I moved it into the door of the box about 10 inches Rating: 5