Try putting the filter right on the fan where you already have the fan hooked up.

And its better to pull air through the filter.
superskunk1 Reviewed by superskunk1 on . odor control Here is my set up: 5'W 3'L 8'H grow tent. 165 cfm 4" Hydrofarm inline fan and a 4" carbon filter. I have the inline fan sitting on top of the top vent whole on the outside of the tent. I used some dryer vent tube to run down into the tent to the carbon filter which i have hanging on its side at the top back of the tent. ( are the filters supposed to be vertical or horizontal ) mine is horizontal right now. for the intake vent i use one of the velcro flaps at the bottm side of the tent which Rating: 5