The town of Libby, Mont., is emerging as a model for how to clean the air by replacing old stoves with new ones. Like Chico, Calif., the town is in a valley where wood smoke can get trapped close to the ground during the winter. So, starting in 2005, the local health department replaced nearly 1,200 older stoves with new wood stoves, pellet stoves or gas or electric heat. They used money from the Environmental Protection Agency, the state of Montana, stove industry and other sources. More