Abstract: A thermostat is arranged to be responsive to the temperature of flue gases from an oil burning heater and actuates switches when the temperature of the flue gases reaches either a predetermined high value or a predetermined low value. The switches are effective, when actuated by the thermostat, to cut off flow of oil to the burner, either by stopping operation of a pump or by effecting closing of a valve in the oil supply conduit. The thermostat is provided with a latch that holds it in the high temperature position, when that position has been reached so that cooling of the flue gases thereafter will not result in resumption of oil flow to the heater. In one form of the invention the same circuit arrangement can be adapted to control either a pump-fed heater or a gravity-fed heater.