Flue-curing is used in Virginia, North Carolina, and the Coastal Plains regions of the U.S. A flue is a chimney or passage that funnels smoke into the curing barn. Flue cured tobacco is used in cigarettes, and is lemon or orange colored. The flue curing process happens in a closed building. Each building has a ventilation system and a heat source. Moisture is automatically removed from the tobacco, and the tobacco changes color. The leaves and stems dry quickly. The process usually takes about a week.