Combustion Air Intake System For Fuel Type Natural Gas Maximum Appliance BtuH Input 450 000 BtuH Maximum Airflow 325 cfm Nameplate Voltage 24V DC Inlet Diameter 6 in Outlet Diameter 6 in Oil Appliance BtuH Input Max of 450 MBH Natural Gas Appliance BtuH Input Up to 450 000 BtuH Minimum Vent Pipe Diameter 4 in Maximum Vent Pipe Diameter 6 in Overall Height 12 1/2 in Overall Length 10 1/4 in Overall Width 9 1/4 in Standards ETL Listed Current 0.8 A