Castle is right about Bears having good info on this topic. I have spent a lot of money in this area. Having family with COPD and Lung cancer, I dont want to play around with my lungs! I just bought another 2 speed fan thats a wall mount with louvers on the outside. I doubt my AC is going to keep up with it. I also wear a fresh air respirator while pouring. Another thing to remember is that if you are sucking air out you need fresh air coming in.