Models 1271C-1 and 1271C-2 Tunnel Corridor Combination Fire/Smoke Dampers are for use where ductwork penetrates the ceiling of an interior corridor of a building, creating a horizontal opening that requires protection. Model 1271C-1 is suitable for use with a steel grille or diffuser when the duct terminates at the ceiling. Model 1271C-2 is suitable for use when the duct is required to continue down past the ceiling level. Each unit is supplied factory mounted in a suitable sleeve complete with upper retaining angles. Model 1271C-3 is both a 1 hr. rated corridor damper for use in corridor ceilings and a standard 1 1/2 hr. rated combination fire/smoke damper for use in walls and floors. The dual rating makes it ideal for stocking as the unit can be supplied when either type of damper is required by the local customer.