What is the primary difference in alarm verification between photoelectric and ionization smoke detectors regarding response to smoldering fires?

The primary difference in alarm verification lies in how each detector type senses smoldering fire particles and interprets alarm signals. Photoelectric smoke detectors excel at detecting larger smoke particles typically produced by smoldering fires because they operate on the light scattering principle. A light beam is directed into a sensing chamber, and when smoke particles enter, they scatter the light onto a photocell, triggering an alarm. Alarm verification in photoelectric detectors often involves analyzing the duration and intensity of the scattered light signal to confirm the presence of sustained smoke, reducing false alarms from temporary disturbances like dust. Ionization smoke detectors, conversely, are more sensitive to smaller, faster-moving particles produced by flaming fires. These detectors contain a small amount of radioactive material that ionizes the air, creating a current between two electrodes. Smoke particles entering the chamber disrupt this current, triggering an alarm. Alarm verification in ionization detectors typically relies on a shorter delay before signaling an alarm due to their rapid response to combustion products. However, their sensitivity to small particles makes them more prone to nuisance alarms from cooking or steam. Therefore, photoelectric detectors, due to their superior detection of larger particles and often more sophisticated alarm verification algorithms, are generally preferred for smoldering fire detection, while ionization detectors may require stricter alarm verification processes to minimize false alarms.