What type of heat detector is characterized as a spot type detector?

A bi-metallic heat detector is characterized as a spot type detector because it detects temperature increases at a specific location rather than monitoring a broader area. This type of detector utilizes two different metals that expand at different rates when heated. When the temperature in the area around the detector rises, the metals bend at a predetermined threshold, triggering an alarm.

This locational sensitivity is what defines it as a spot type detector; it is designed to react when temperature thresholds are reached specifically at that point. This is particularly useful in environments where localized heat detection is necessary, such as in mechanical rooms or near equipment that might generate excessive heat.

In contrast, other types of detectors, such as ionization and photoelectric detectors, are used for smoke detection rather than heat detection. Rate-of-rise detectors, while also heat detectors, monitor temperature changes over time rather than being location-specific.