When one thinks of wood stoves, something that may spring to mind is smoke. It is true that all wood stoves, even the most efficient ones, produce some smoke. And air pollution is certainly a major concern these day everywhere, but especially in localities with the most unhealthful levels of air pollution. I happen to live in the region with the worst air pollution in the United States of America, the San Joaquin Valley of California. The main cause is that air pollution from a variety of sources, especially automobiles, is emitted — particularly in the dry season from May to November — but it is not often removed from the air by precipitation nor by wind in the relatively still air of the Valley, which is hemmed in by two mountain chains.