NCIDQ IDFX Practice Exam

Which detector is considered useful where fire smoke is minimal before flames erupt?

1. Flame detector

2. Rise-of-temperature detector

3. Photoelectric detector

4. Ionization detector

The correct answer is: Photoelectric detector

The photoelectric detector is considered particularly useful in environments where fire smoke is minimal prior to flames erupting because it is designed to detect smoldering fires. This type of fire is characterized by slow combustion that produces smoke without significant flames initially. Photoelectric detectors use a light source and a sensor to detect the presence of smoke particles in the air. When smoke enters the detection chamber, it scatters the light beam, triggering the alarm. Since these detectors are sensitive to the small and often less visible particulates produced by smoldering fires, they can provide early warnings even when flames are not yet present or when smoke is very minimal. In contrast, other types of detectors, such as flame detectors, are best suited for situations where flames are already visible, as they require direct sight of the flames to activate. Rise-of-temperature detectors respond to significant increases in temperature and might not provide early warning in the case of smoldering fires. Ionization detectors, while effective for fast-flaming fires, are less sensitive to slow smoldering fires, as they rely on detecting ions produced by combustion in a flaming environment.