Which detector responds best to smoldering fires with heavy smoke?

• A. Photoelectric detectors
• B. Ionization detectors
• C. Dual-sensor detectors
• D. Heat detectors

Answer: (A)

Smoldering fires produce a lot of visible smoke with little flame. Photoelectric detectors sense smoke by detecting light that is scattered inside a chamber when smoke particles pass through. The dense smoke from smoldering fires scatters more light and reaches the sensor quickly, so the alarm trips sooner than with other detector types. Ionization detectors, which rely on ionized air to detect changes caused by flame particles, respond fastest to flaming fires, not dense smoke. Heat detectors only sense temperature rise and do not respond to smoke at all. So, for smoldering fires with heavy smoke, photoelectric detectors are the best choice.