What characteristic distinguishes a photoelectric smoke detector?

A photoelectric smoke detector is distinguished by its use of light to detect smoke. This type of detector operates based on the principle of light scattering. When smoke particles enter the detection chamber, they scatter the light emitted by an internal light source (typically a laser or LED), which triggers the alarm. This makes photoelectric smoke detectors particularly effective in detecting smoldering fires that produce a lot of smoke before flames develop, as they can respond to the presence of smoke even at low levels.

In contrast, the other characteristics listed do not accurately describe photoelectric smoke detectors. For instance, measuring heat levels is a feature of heat detectors, not smoke detectors. Responding to fast-flaming fires is a trait more commonly associated with ionization smoke detectors, which are more sensitive to rapid flame fires. Although some smoke detectors may have a longer lifespan, this is not a characteristic exclusive to photoelectric types and can vary among different types and brands of detectors. Thus, using light to detect smoke is the defining feature of a photoelectric smoke detector.