What does the sensing element in a pneumatic thermal fire detection system consist of?

The sensing element in a pneumatic thermal fire detection system is generally comprised of a helium-filled tube connected to a responder assembly. In this type of system, the thermal expansion of gases is utilized for fire detection. As temperature increases due to a fire, the gas inside the tube expands, increasing the pressure. This change in pressure can be sensed and used to trigger an alarm or activate a responder assembly, indicating the presence of fire.

This design is advantageous because it operates without the need for electrical components within the detection area, which minimizes the risk of false alarms and enhances reliability in harsh environments. The characteristics of the helium gas contribute to the system's responsiveness to temperature changes, making it effective for early fire detection.