Ruskin Model IBD2 1 1/2 hour UL classified static (fans off) curtain style fire damper for use in HVAC systems that shut down during a fire event. Fire dampers used for the protection of openings in walls, partitions, or masonry floors with fire resistance ratings of less than 3 hours and shall have a 1 1/2 hour fire protection rating. The IBD2 can be installed vertically in walls or horizontally in masonry floors and is rated for airflow in either direction.