Design 0540V Large Body Static Curtain Hearth Damper is UL authorised for use in which making codes require the protection of HVAC ductwork penetrations in vertical fire separations (walls or partitions) that have a fire resistant rating of 4 hours or considerably less. The 0540 is classed for use in https://dampersforindustrialsecto35567.thelateblog.com/37483261/heavy-duty-stainless-steel-damper-manufacturers-an-overview