Well, you asked a complicated question that is pretty easy to answer... and since, nobody else has stepped up... I'll try to paint with broad strokes here... A smoker works just like an indoor convection oven, only with smoke, from burning wood of some sort (wood, charcoal, lump, pellets etc.), involved... That is you have heated air moving around the cook chamber and around the food... In the most basic configuration, a firebox on one end, a cook chamber in the middle and an exhaust stack on the other. The heated air from the firebox moves through the cook chamber and out of the stack creating a draft (moving heated air/smoke particles). Now there are various other designs, like the
Weber Smokey Mountain and such where you have the coals underneath the food with a barrier of some sort such as a water pan in between the fire and food, but they follow the same principals of moving heated air/smoke past the food to cook it.
Humidity in the pit is created in a few ways. First, burning wood (unless it is bone dry and therefor, not providing much flavor, but well seasoned wood is best) will release moisture from water trapped within. The meat itself will give up moisture as it cooks and the fat and collagen melts and breaks down releasing the water trapped there in. If you have a well sealed pit, a lot of this moisture will remain in the pit, some, of course, will go out the stack with the air flow. You can also introduce humidity in a pit by using a water pan, tray etc.
Keeping the end product nice and juicy/moist is where the art of BBQing lies.. You need to balance cooking temps and time to reach internal temps and texture of the various meats you are cooking. All along the way, you need to keep a clean burning fire to give you that smokiness that you are trying to achieve from BBQing in the first place and to avoid the dreaded creosote that ruins so many early attempts of the BBQ newbie...
Did any of this make sense? If not ask and I will try to break it down further...
James.
