Products Architectural Louvers, Dampers, Roof Curbs, Actuators, Grilles, Sunshades and more. Dampers - Rectangular Industrial Dampers: Model:NAH-721-1 Parallel Blade, Heavy Duty, Flanged, All Steel, Airfoil Blades, up to 20" w.g. APPLICATION The model NAH-721-1 is a heavy duty flanged frame style industrial control damper that has steel formed airfoil blades. NAH-721-1 DOCUMENTS - Submittal Sheet - NAH-721-1 BIM (REVIT) - Bearing Chart Drop Plenum Diffusers Balancing / Regulating Dampers UV Products Iris Dampers Louvers Dampers UL Listed Dampers Roof Curbs and Rails Sunshades Architectural Grilles Ventilators Doors Actuators Fans Air Measuring Products VAV Terminals Security Bars & Grilles Plenums Duct Take-Offs Custom Work Manufacturer Cross Referencing System View Now Previous Next