Hi there. Hoping someone can help. My grow closet is 20.5x 4ft. I just ordered a 4" fan and carbon filter with speed control. Wondering if I should push or pull. Entire fan and filter inside the grow space or should I have the fan and filter outside of the space or maybe some other combo? I don't have a ton of space. What will work best? Any help would be greatly appreciated as I am building the space now. Thanks.