I have a 4x2 tent with just a 4'' carbon filter and 4'' fan for exhaust. No intake. I just leave the holes open on the tent. I have a 9'' fan outside the tent blowing air through a hole on the bottom of the tent. I have a 9'' fan on top of the tent blowing air through the hole on the top. I also have two 6'' clip on fans blowing air across the top of the plants in the tent.