More people are turning to wood to heat their homes and some are using outdoor wood furnaces. But those furnaces are causing air pollution problems that in some cases have neighbors complaining about smoke drifting into their yards and homes.
Nationally, the Environmental Protection Agency regulates indoor wood stoves but issues only voluntary guidelines for outdoor wood furnaces.
Vermont adopted emission standards for wood boilers in 2007. Last week, Vermont, New Hampshire and Maine stiffened their standards for new furnaces. Newer models are up to 90 percent cleaner and use up to 50 percent less wood.
Other regulations have been proposed in Connecticut, Indiana, New York, Pennsylvania and Ohio. Some communities regulate the furnaces themselves.