How Do Smoke Detectors Work

How do smoke detectors work? Learning that could ultimately save your life. Each fire takes on its own personality, of sorts. While some fires produce fast-moving flames, others smolder and create a lot of smoke. Preventing each type requires a different style of smoke detector. Let's take a look at how smoke detectors work.

Ionization Alarms
An ionization detector contains a radioactive material, americium-241, within a metal chamber. Two metal plates are powered by a battery. One plate has a positive charge; the other, negative. The americium-241 releases alpha particles that collide with oxygen and nitrogen in the chamber, producing charged particles that create current.

When the current is interrupted by smoke entering the chamber, the smoke particles stick to the charged ions, causing them to return to a neutral condition. Heat enters the chamber and the ionization rate changes the current amount. Now, the alarm triggers.

An ionization detector works best for fast-spreading fires that have minimal amounts of smoke.

Photoelectric Alarms
A photoelectric smoke detector depends on two parts: a beam of light and a photoelectric sensor. Instead of a parallel connection, a photoelectric detector works on a 90 degree angle. A light beam shines across, but when smoke particles deflect light onto the detector, smoke also fills the chamber. This creates a current and sounds the alarm.

A photoelectric alarm detects smoky, slow-burning fires.

Dual-Sensor Alarms
Dual-sensor alarms, which use both ionization and photoelectric detectors, are on the market. These combination alarms may be a better safety option since smoke and slow- and fast-moving fires are detected.

Installing a smoke detector may be the smartest safety decision you will ever make. Smoke detectors can save your life and your family's lives, as well as protect your household.

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