Flame detectors are used to detect fire by sensing the light produced by flames.
They can detect ultraviolet (UV) or infrared (IR) radiation emitted by combustion.
Light Emission Diode (LED) is a light source, not a detector.
Heat detectors respond to temperature changes, not light.
Smoke detectors sense particles in the air, not light spectrums.
Therefore, the correct answer is Flame Detector.