What components are heat-sensitive units that complete electrical circuits at a specific temperature?

The answer is thermal switches. These devices are specifically designed to respond to temperature changes by completing or breaking an electrical circuit at a predetermined temperature. When the temperature rises to the set point, the thermal switch activates, allowing electricity to flow through the circuit. This feature is critical in fire detection systems, as it allows for an immediate response to overheating, which could indicate a fire hazard.

Thermal switches are beneficial in various safety applications because they can provide a clear and reliable indication of overheating conditions. Their straightforward mechanism of operation—opening or closing a circuit based on temperature—makes them easy to integrate into fire detection systems, ensuring a reliable response when temperatures exceed safe limits. In contrast, other devices, such as thermocouples, flame detectors, and pneumatic detectors, have different functions and operational principles that do not focus solely on simple temperature thresholds for completing electrical circuits.