Design Sequence 1220M and 1220M-3 "3-in-one" Modulating Fire/Smoke Dampers are already engineered to supply premium containment in hearth and smoke disorders. The addition of volume Regulate using a modulating actuator eradicates the necessity and price of the independent Command damper. See Item Details Design 0540V Broad Frame Static Curtain Hearth https://dampers-for-industrial-se91122.blogdanica.com/36981847/dampers-for-industrial-sector-an-overview