How does a thermocouple fire detection system detect fire?

A thermocouple fire detection system operates based on the principle of measuring temperature and detecting changes in temperature over time. It consists of two different metal wires joined at one end, creating a junction that generates a voltage output when there is a temperature difference between the junction and the other ends of the wires.

When a fire occurs, the temperature rises rapidly around the thermocouple. The system senses this increase in temperature and triggers the alarm or response protocol. The reliance on the rate of temperature rise makes it particularly effective for early detection of fires, as rapid increases in temperature can indicate the presence of flames or other combustion processes.

The other options involve methods that are not applicable for thermocouple detection systems. Humidity levels, pressure changes, or smoke quantity do not directly contribute to how thermocouples function, as they are specifically designed to detect thermal variations instead. This focus on temperature measurement is what makes option C the correct and suitable choice in the context of thermocouple fire detection systems.