Photoelectric Vs. Ionization Smoke Detectors

History

• Smoke detectors were first invented, by accident, in 1930 by a Swiss physicist attempting to make a device to detect poison gas. His experiment failed, but when he lit his cigarette after the failure and the alarm sounded, the smoke detector was born.

Ionization Alarms

• Ionization alarms contain a minute amount of radiation that ionizes air in the detector. When smoke fills the chamber, this disrupts the ionization. These alarms are best used in detecting flash fires.

Use of Radiation

• While there is radiation in ionization detectors, the radiation level is so small that it has virtually no effect on humans, even if the radioactive unit on the detector is somehow dislodged and swallowed by a small child.

Photoelectric Alarms

• Photoelectric alarms work by way of a light projected into the alarm chamber. When smoke, such as that from a smoldering fire, enters the chamber, it disrupts the light flow, causing an alarm.

The Better Detector

• Both detectors work well in detecting fires. Ionization alarms are more common, but the photoelectric detectors are less susceptible to false alarms.