Which statement describes the thermal switch fire detection system components?

• A. A photoelectric sensor and smoke chamber.
• B. A gas-filled tube and pressure sensor.
• C. Temperature sensitive switches that complete a circuit at a specific temperature and trigger a warning.
• D. An infrared sensor and fan.

Answer: (C)

Thermal switch fire detection relies on a temperature-sensitive element that changes state at a preset temperature. When heat from a developing fire reaches that threshold, the switch completes a circuit and triggers a warning. This simple, heat-activated mechanism provides a direct indication of elevated temperatures associated with fire, independent of smoke or flame radiation.

Other detectors operate differently: photoelectric sensors with a smoke chamber detect smoke particles; gas-filled tubes with a pressure sensor sense gas changes or leaks; infrared sensors with a fan detect radiant flame heat and sample air. None of these describe a temperature-threshold switch that closes a circuit to warn.