The smoke exhaust fire damper is installed on the smoke exhaust pipe. Its working principle is that when the fire smoke temperature in the smoke exhaust pipe exceeds 280 ℃, its fusible metal sheet condenses, and actively close the smoke exhaust fire damper to prevent the fire from spreading through the smoke exhaust pipe. The structure of fire damper is mainly composed of valve body and actuator. The valve body is composed of shell, flange, blade and blade connecting rod mechanism.

執行機構由殼體、葉片調度機構、離合器、溫度熔斷器等組成，防火閥執行機構通過金屬易熔片和離合器機構控制葉片的滾動。當管路中的氣體溫度達到易熔金屬片的冷凝溫度時，易熔金屬片熔化，芯軸上的緊固拉簧和拉簧銷迅速使離合器底板斷裂。

The actuator is composed of shell, blade dispatching mechanism, clutch, temperature fuse, etc. the fire damper actuator controls the rolling of blades through metal fusible plate and clutch mechanism. When the gas temperature in the pipeline reaches the condensation temperature of the fusible metal sheet, the fusible metal sheet melts, and the fastening tension spring and tension spring pin on the mandrel quickly break the clutch bottom plate.

此時，離合器和葉片調度機構分離，由于閥體上安裝了兩個變張力彈簧，葉片扭曲和滾動。由此可見，防火閥的執行機構采用機械傳動原理，不需要電、氣等動力，保證在任何情況下都能起到防火的作用。根據系統要求，當系統停用或正常運行時，防火閥開啟。如果管道中的氣體溫度低于所選金屬易熔片的熔點，則防火閥處于正常工作狀態，閥門打開。只要工作條件超過正常工作條件，閥門就會主動關閉以實現其功能。

At this time, the clutch and the blade dispatching mechanism are separated. Because two variable tension springs are installed on the valve body, the blades twist and roll. It can be seen that the actuator of the fire damper adopts the mechanical transmission principle and does not need electric, pneumatic and other power to ensure that it can play the role of fire prevention in any case. According to the system requirements, when the system is out of service or in normal operation, the fire damper will be opened. If the gas temperature in the pipeline is lower than the melting point of the selected metal fusible sheet, the fire damper is in normal operation and the valve is opened. As long as the working conditions exceed the normal working conditions, the valve will actively close to realize its function.