Which detector is commonly favored for detecting smoldering fires in spaces with dense smoke?

• A. Ionization Detector
• B. Photoelectric Detector
• C. Heat Detector
• D. Flame Detector

Answer: (B)

Photoelectric detectors are especially good at sensing smoldering fires in dense smoke because they detect smoke by light scattering. Inside the sensor, a beam of light is aimed across a chamber; when smoke particles fill the space, they scatter that light, and some of the scattered light reaches the sensor and triggers the alarm. Smoldering fires produce a lot of smoke without bright flames, so the visible haze is what these detectors respond to most quickly.

Ionization detectors, by contrast, rely on ionizing air to create a current and tend to respond faster to flaming, hot fires with smaller smoke particles. Heat detectors go off only when temperatures rise significantly, and flame detectors look for actual flame radiation with line-of-sight visibility. Therefore, in spaces filled with dense smoke from a smoldering fire, the photoelectric detector offers the quicker, more reliable response.