Participate and Gaseous Emissions from Natural Gas Furnaces and Water Heaters

Three furnaces and one hot water heater were tested for particulate and gaseous emissions. The effects of fuel, stoichiometry, operating conditions, and appliance type on emission levels were studied. The filterable particulate levels from a properly operating furnace were very low. However, condensable particulate emissions were considerably greater, approximately the same as predicted by EPA estimates of furnace particulate emissions. Carbon emissions comprised about 12% of filterable particulate emissions. However, when operated highly fuel-rich, copious amounts of elemental carbon particles were emitted with a mass median diameter of less than 0.4 μm. Gaseous emissions were dependent on cycling of the furnace and stoichiometry.

An estimate was made of the daily furnace emissions compared to daily emissions from a 1980 catalyst-equipped automobile. While gaseous emissions were less than the corresponding vehicle emissions, the particle emissions from the furnace were three times greater than particle emissions from a 1980 vehicle.