Abstract: A domestic furnace for heating a fluid that is circulated through a residential building includes an oil burner, a firebox for combustion products of the burner, a heat exchanger and a flue. A conduit extending from outside of the building supplies outside air to the burner and to the flue through a pressure controlled damper; the combustion air supplied to the burner is filtered. The air inlet to the burner includes a damper that closes automatically when the burner is extinguished, to eliminate heat losses up the flue during furnace standby. Nitric oxide, carbon monoxide, unburned hydrocarbon, and smoke emissions are minimized by the design of the burner and firebox combination. A conventional type burner head is used, rather than a flame retention type, and its choke diameter is related quantitatively to the burner firing rate. In addition, the burner head has oversized, internal, peripheral air swirler vanes.