Ok so with a 150w hps you are going to almost be at 10000 lumens per sq/ft. That is the power of the sun. So light wise you are doing great. Unfortunately I have never seen a cool tube for a 150 but you can still get an air cooled hood. Use your 6" fan to cool it sucking cool air from outsid your space and exhaust it back outside. No smell because it is a "closed" system. Grab a bath fan from a home supply store, a 50 Cfm will be fine. You have 9 cubic feet so a 50 would exhaust the whole room in seconds. normally you have a 3" or 4 " opening for exhaust with one of those so make your own carbon filter and voila. No heat or smell concerns. I miss the days when I was going small. The bigger the grow room the more logistics to contend with......good luck.
Thanks for the info. The inline fan I bought a while back came with a beastly carbon filter (9in. diameter). I had planned initially to have it hanging from the inside of my cab. Upon seeing it in person, however, I knew immediately that I'd have to come up with another plan. I have it outside the cab, masked with the bottoms of my shirts hanging from the clothes rod above. At the moment, I leave the cab door cracked slightly to let in fresh air. This takes away from my lighting though, so it's only temporary. I'll have to drill a hole here soon. That's the downfall of having a metal cab. Drilling holes is a bitch.
My next, and hopefully last (at the moment, anyway) purchase will be another little USB fan for air circulation. I hope to somehow rig it to the bottom of my light to rush that hot air directly to my exhaust.
One concern I have is the temperature of my little grow space. Now that I've installed the new light, my temps, which weren't ideal to begin with, are now creeping up to the high eighties. My exhaust is overkill, I have a powerful little fan, and leave the cab door cracked AND closet door open; so, I'm not sure what else I can do.
The plants seem to be doing OK overall. Two (Bubba's Gift and a bagseed) are coming along slowly but surely. The other (bagseed), which developed more quickly than the others, is developing brown spots. I over-watered at first, but have since stopped watering so frequently and heavily. Not sure if it will make it. It's strange that the others don't show any symptoms, though.
Sorry for the short story. LOL. I appreciate your input.