The Tri-Stage Intake Air Filter System comes in 3 sizes with capacities of 6,000 to 40,000 cfm. The hinged louver section allows easy access to change filter elements and is available with a choice of weather louver section or dust louver inertial separator as first stage. Tri-Stage Intake Air Filter Systems are manufactured with 7 gauge plate welded construction and galvanized weather louver and filter holding frames. Draft gage and pressure swith come standard.