The damper is made of a black steel coating with thickness of 3 mm and a main valve with thickness of 5 mm, reinforced with flat rods 50x5, fixed on a shaft with diameter of 45 mm. The shaft is fixed on two bearings with external lubrication outside the insulation. In order to minimize the temperature influence on the controlling pneumatic actuator's operation, its fixation is also placed outside the insulation. The damper has two positions, open (actuator in position 1) and closed (actuator in position 2). Depending on the needs, it is possible to set a solenoid valve that controls the actuator into the operation mode NC (normally closed) or NO (normally open). The maximum medium speed should not exceed 22 m/s. The damper is adapted to operation with flue gases with a temperature up to 200 °C.