Do you have an exhaust fan? You will not be able to run a 400 MH without one. A duct booster fan will not cut it, though--do not waste your money. Yes, I have a 4" centrifuge type fan in the space connected to the light with ducting and then it is ducted out of the tent. But I am sucking the air through the light, not blowing it through the light--you want negative pressure in your space. The intake is passive. This morning, it is 64F in the room the tent is in and the tent is running at 71.5F. Fan is running on low. I can post up a pic later if you would like?