Combustion Air Intake System For Fuel Type Natural Gas and Oil Maximum Appliance BtuH Input 850 000 BtuH Maximum Airflow 250 cfm Nameplate Voltage 120V AC Compatible System 120V Appliance 24V Gas Appliance 750 mV Gas Appliance Inlet Diameter 8 in Outlet Diameter 8 in Oil Appliance BtuH Input Up to 775 000 BtuH Natural Gas Appliance BtuH Input 450 000 BtuH Minimum Vent Pipe Diameter 8 in Maximum Vent Pipe Diameter 8 in For Maximum Duct Length 100 ft Overall Height 9 1/2 in