Smoke and fire dampers are mainly used in the air ducts of ventilation and central air conditioning systems, and are normally in the "open" state. When the air temperature reaches 70℃, they close automatically through the action of the internal switch.  
Smoke exhaust outlets and smoke exhaust valves are mainly installed in the pipelines of the smoke exhaust system, or at the suction inlet of the fire-fighting smoke exhaust centrifugal fan (for electric smoke exhaust valves), and are normally in the "closed" state. In case of fire, they open automatically for smoke exhaust through linkage control.  
Smoke and fire dampers are installed at the inlet of centrifugal fans used in both smoke exhaust systems and HVAC systems. They are normally in the "open" state to allow ventilation. When the air temperature in the pipeline reaches 280℃, the valve closes automatically through the action of the temperature-sensitive switch of the fusible metal, cutting off the air flow and preventing the spread of the accident.  
In some types of building fire protection projects, such equipment is used continuously. The Business Center of Chongqing Tobacco Company is one such example.