Which type of heat detector is held in place by a solder with a specific melting point?

A fusible device is designed to operate based on the melting of a solder that is held in place at a specific melting point. When the ambient temperature rises to that designated level due to fire conditions, the solder melts, allowing the device to trigger an alarm or activate a suppression system. This makes fusible devices particularly effective for detecting fires because they respond to heat rather than smoke or gas, providing a straightforward mechanical action that leads to a reliable response in fire situations.

In contrast, thermistors measure temperature changes electrically, while photoelectric devices and ionization detectors rely on light or ionization in the air to detect smoke particles. These other types of detectors operate on different principles and are not dependent on a physical change, such as the melting of a solder, to function. Thus, a fusible device is unique in its operation and effectiveness in specific firefighting scenarios.