A vertical water smoker (also referred to as a bullet smoker because of its shape) is a variation of the upright drum smoker. It uses charcoal or wood to generate smoke and heat, and contains a water bowl between the fire and the cooking grates.The water bowl serves to maintain optimal smoking temperatures and also adds humidity to the smoke chamber. It also creates an effect in which the water vapor and smoke condense together, which adds flavor to smoked foods. In addition, the bowl catches any drippings from the meat that may cause a flare-up. Vertical water smokers are extremely temperature stable and require very little adjustment once the desired temperature has been reached. Because of their relatively low cost and stable temperature, they are sometimes used in barbecue competitions where propane and electric smokers are not allowed.