Blumenthal said Wednesday that the furnaces burn wood at low temperatures, the Hartford Courant reported. The furnaces are basically metal sheds holding wood-burning stoves surrounded by water, which is heated and then piped into a home.
"Complaints have dramatically proliferated as these furnaces become more prevalent -- more homeowners burning wood in outdoor furnaces to avoid the higher cost of oil or natural gas in tough economic times," Blumenthal said.
Three Connecticut towns have banned the outdoor furnaces. Under state regulations, they must be at least 200 feet from the nearest house and have smokestacks higher than the roofs of any homes within 500 feet.
The furnaces "spew toxic smoke 24 hours a day, seven days a week, sickening neighbors and contaminating neighborhoods," Blumenthal said. Some owners also use them to incinerate trash, adding to the problem.