Abstract: A damper assembly constructed to close a flue pipe for a burner during non-use of the burner and to automatically open prior to burner ignition. An actuator operated by a thermo-statically controlled heater and an expansible fluid, rotates a baffle of the damper assembly to open the flue pipe. A safety interlock requires the baffle to be opened before the burner is ignited. When the burner is turned off, the actuator delays closing of the baffle for a time to allow exhausting of residual combustion products. In one embodiment, two baffles are operated to close a flue pipe above and below a draft diverter.