The shut-off (butterfly) fire dampers are manufactured in the following nominal sizes: DN100, DN125, DN160, DN200, DN250. The fire dampers are equipped with a thermal fuse mechanism ensuring the damper switch to the safe position in case of reaching an ambient temperature equal to or higher than 72°C. The fire dampers allow using limit switches signalling closed position of the damper blade (1 limit switch) or blades (in case of using 2 limit switches). The casing is made from galvanised steel sheet; the fire damper blade is made from a silicate cement board.