I'm in the process of building a vertical smoker with a domed top (rectangular unit). Yesterday, mid 70's-no wind- I lit it off for the first time. Used approx. 2 charcoal starters of lump charcoal in the charcoal basket and a good handful of soaked orange wood branches. No meat as this was a test burn. Exhaust worked fine; just an adjustable flap at the dome, HOWEVER, the intake has me baffled ! Due to the fact that this is still in developmental stages I wanted to see how hot it would get before starting on a intake damper. Now I know that by shutting down the intake and exhaust you can close off the fire. This unit has no intake and no matter how I adjusted the exhaust I couldn't keep it below 275, until after 2 1/2 hrs, when the charcoal started to burn out. My first thought was too much leaking air, but if that was the case why didn't smoke come pouring out of these voids as it does in my horizontal side box? Thinking more and a few more Heineken's later, I thought about possibly placing 1" or 2" of play sand on the bottom, below the coal basket, to line the bottom and perhaps a 10" bowl of either water or sand to act as a heat sink. If the temps dropped too low I could then add the intakes. To verify that I didn't have any air leaks, later that night I dropped a light bulb down through the exhaust and found no evidence of light escaping from any seams. If any of the astute panel members here could add any input it would be greatly appreciated. Thanx, The Cap'n.