How does a photoelectric type smoke alarm work?
A photoelectric type smoke alarm consists of a light emitting diode and a light sensitive sensor in the sensing chamber. The presence of suspended smoke particles in the chamber scatters the light beam. This scattered light is detected and sets off the alarm. • Which type of alarm is more effective? There is no simple answer to this question. The two types operate on different principles and therefore may respond differently to various conditions. Some advantages to each type are set out below: Ionization • Fastest type to respond to flaming fires • Lowest cost and most commonly sold • Some models have a hush or temporary silence feature that allows silencing without removing the battery • Some models are available with a long life battery Photoelectric • Fastest type to respond to slow smoldering fires and white or gray smoke • Less prone to nuisance alarms from cooking Notwithstanding these differences, to achieve ULC listing, both alarms must be tested to the same standard and meet
