BAS-CVS Static Fire Dampers are intended for use only in static HVAC systems which automatically shut down in the event of a fire. BAS-CVS static fire dampers are available in a wide range with 1-1/2-hour & 3-hour fire endurance ratings. As required by the NFPA-90A Chapter 5 & IBC Chapter 7, 1-1/2-hour fire dampers are required in walls, floors, and partitions with a fire-resistance rating of less than 3-hours; whereas, 3-hour dampers are applied when there are fire ratings of 3-hours or more.