call me lucky but I run like this. 6" dia. Carbon filter up high......4" can fan... the green generic one.....insulated (pricey) 4" ducting through 3 600w either MH of HPS in a straight line....these are sealed 6" hoods with reducers....more 4" ducting....out through 4" flange in blacked out door......It's nice and cool.......OH wait i'm an idiot........I have a portable air conditioner I got for 50 bucks on craigslist.......Get an air conditioner......I vent it through that pricey 4" ducting also.......I found the ducting for the big box stores makes a fk load of noise like a flute...........$19 bucks for 25 feet a the good stuff and its dead quiet on the exit side.....my room is mostly sealed and i get frest air from the house...That comes in through carbon filter from HVAC section at the big box stores.....1 other thing my hoods had tiny leaks on two sides where the glass dipped a little as its only supported on two side....tape that area up as on the third light it was like a little blowdryer of hot air......