Source: I Love Grilling Meat
Back in 2010, I led a trip of food writers to a relatively new place called Franklin Barbecue that was set up in a series of trailers in a parking lot off Interstate 35 in Austin. The Moores use an offset barrel smoker made from an old industrial propane tank, much like the smokers used by Franklin and Timmons. According to Moore, one of the most important factors in cooking barbecue is humidity, the amount of moisture in the air. Neither I nor Moore can claim to know the exact physics associated with this, but you might think about it in terms of "wet" heat.