Details test and examination criteria for electrically operated and thermally actuated automatic vent damper devices which are capable of being installed in venting systems, in the outlets of or downstream of appliance draft hoods, of existing individual, automatically operated listed gas-fired appliances. An electrically operated vent damper device employs electrical energy to control the device. A thermally actuated vent damper device depends for operation exclusively upon the direction conversion of the thermal energy of the vent gases into mechanical energy.