What triggers an internal switch to close in a pneumatic thermal fire detection system?

In a pneumatic thermal fire detection system, the internal switch is designed to respond to changes in gas pressure that occur when certain conditions, such as high temperatures, are met. As a fire generates heat, this heat causes the gas within the system to expand and increase in pressure. When this pressure rises to a specific threshold, it triggers the internal switch to close. This action is vital for alerting that a fire may be present, allowing for appropriate safety measures to be taken.

The design of pneumatic systems relies on the physical properties of gases, particularly how they respond to temperature changes, making the relationship to pressure increase a fundamental aspect of their operation. This helps in providing a reliable detection mechanism that reacts to the immediate environment's thermal conditions.