UD Smoker?

I've been using a UD smoker with charcoal for several years and I'm not dead, so I guess its safe. I have tried a couple other types of smokers including a propane cabinet type, and the UD is my favorite by far. In my experience, it works good because it is a completely sealed chamber. The only combustion air that is introduced is whatever you let in. Mine is pretty simple, I have 3 pipe nipples at the bottom, two have caps and one has a valve. I have found that allows enough adjustability to be effective. The lid on mine has a threaded hole, so i have a piece of 2" rigid conduit threaded into it as a chimney. I've had plenty of good eatin' come out of it!!