Which fire detector responds to a predetermined temperature or an increase in temperature?

The thermal detector is specifically designed to respond to changes in temperature or to a predetermined temperature limit. These detectors typically utilize a thermally sensitive element that detects heat. When the temperature reaches a specified threshold, or when there is a significant increase in temperature over a short period, the detector activates an alarm.

In contrast, ionization detectors and photoelectric smoke detectors function primarily based on smoke particles or ionized air rather than direct temperature changes. Ionization detectors are sensitive to particulate matter from combustion, while photoelectric smoke detectors work by detecting light that is scattered by smoke particles. Infrared flame detectors are typically used to detect flames based on infrared radiation but are not focused on temperature changes in the same predetermined way that thermal detectors are.

Thus, the primary function of thermal detectors in fire protection systems is to effectively provide an early warning based on temperature variations, making them a vital component in many fire alarm systems.