Furnaces and boilers

"Most U.S. homes are heated with either furnaces or boilers. Furnaces heat air and distribute the heated air through the house using ducts. Boilers heat water, and provide either hot water or steam for heating. Steam is distributed via pipes to steam radiators, and hot water can be distributed via baseboard radiators or radiant floor systems, or can heat air via a coil. Steam boilers operate at a higher temperature than hot water boilers, and are inherently less efficient, but high-efficiency versions of all types of furnaces and boilers are currently available. To learn more about furnaces, boilers and other types of home heating systems, explore our Energy Saver 101 infographic on home heating..."
Energy efficiency:Furnaces-and-boilers

EPA Establishes Clean Air Act Standards for Boilers and Incinerators
" In response to federal court orders requiring the issuance of final standards, the U.S. Environmental Protection Agency (EPA) is issuing final Clean Air Act standards for boilers and certain incinerators that achieve significant public health protections through reductions in toxic air emissions, including mercury and soot, but cut the cost of implementation by about 50 percent from an earlier proposal issued last year.

Mercury, soot, lead and other harmful pollutants released by boilers and incinerators can lead to developmental disabilities in children, as well as cancer, heart disease, aggravated asthma and premature death in Americans. These standards will avoid between 2,600-6,600 premature
deaths, prevent 4,100 heart attacks and avert 42,000 asthma attacks per year in 2014..."