Which of the following is NOT a type of smoke detector?

A thermal detector is designed to respond to changes in temperature, not directly to smoke particles, which makes it distinct from smoke detectors. Smoke detectors primarily focus on detecting the presence of smoke as an indicator of fire.

Photoelectric detectors function by using a light beam and sensing smoke particles that disrupt the light, signaling a presence of fire. Ionization detectors work on a different principle, utilizing radioactive material to ionize air and detecting changes in current caused by smoke particles. Combination detectors merge the technology of both photoelectric and ionization detectors to offer comprehensive protection against different types of fires.

By recognizing that thermal detection does not classify as a smoke detection method, we can clarify that thermal detectors are valuable for monitoring temperature increases but are not categorized as smoke detectors.