A tobacco-drying kiln, also known as an OAST, is a type of kiln used to dry cured tobacco leaves. The OAST is typically a large, cylindrical structure with a conical roof and a door at the base. Inside, the kiln is lined with brick and heated by a fire, usually fueled by wood or coal. The heat from the fire is circulated throughout the kiln, drying the tobacco leaves and giving them their characteristic flavor.