What is a snap disk heat detector?

• A. A detector using a disk that snaps at a set temperature
• B. A detector that uses ionization to detect smoke
• C. A detector that uses a photoelectric chamber
• D. A detector with a thermal camera

Answer: (A)

A snap disk heat detector relies on a small disk that physically snaps at a preset temperature to trigger the alarm. This fixed-temperature mechanism, usually a bimetallic disk, closes a circuit when the ambient heat reaches its rated point, signaling fire conditions. It detects heat rather than smoke, which is why it’s different from ionization or photoelectric smoke detectors. It’s a simple, inexpensive type of heat detector, suitable in environments where smoke detectors might give false alarms, though it may be slower to respond to rapid fires.