A stove is an enclosed space in which fuel is burned to provide heating, either to heat the space in which the stove is situated, or to heat the stove itself and items placed on it. This article is principally concerned with enclosed stoves burning solid fuels for room heating. A kitchen stove is used to cook food. A wood-burning stove or a coal stove is typically used for heating a dwelling. Enclosed stoves are more efficient and prevents air from being sucked from the room into the chimney. Due to concerns about air pollution, efforts have been made to improve stove design. Pellet stoves, for example are a type of clean-burning stove. Air-tight stoves more completely combust wood and eliminate polluting combustion products. In the U.S. since 1992, all wood stoves being manufactured must limit particulate emission.