I don't know at all how to put in an inline fan or exhaust fan.......this is for the empty tent in the picture....I do think it should come out of the top just because it prolly easier....??? In the picture showing both tents,, in the short tent I used a flange with a inline fan like the one in the picture from the top. Need 8 inch for the top of empty one... should I use duct tubing ? What kind of fan ???The bottom has 3 mesh vents..oh forgot and empty tent is 4x4 , 70 something tall. That's all I can think of right now. Thanks I'm having a problem with pictures, please bare with me....can't cancel my post, it won't do it.