What type of heat detector includes a mechanism that uses two metals responding differently to heat?

The type of heat detector that includes a mechanism where two metals respond differently to heat is known as a rate-of-rise heat detector. This device is designed to sense a rapid increase in temperature over a short period of time, which often indicates a fire's onset. The mechanism consists of two metals, typically soldered together, that expand at different rates when subjected to heat. This differential expansion causes the metals to bend and ultimately trigger the alarm when the temperature rise exceeds a specific threshold.

This characteristic makes rate-of-rise heat detectors particularly effective in environments where sudden changes in temperature may indicate an imminent fire hazard. They are distinct from fixed-temperature heat detectors, which activate at a specific temperature regardless of how quickly that temperature is reached. Understanding the operational principles of these detectors is crucial for effective fire prevention and safety measures in various settings.