How Fire Alarm Systems Work

How Fire Alarm Systems Work

Summary: To date there are two types of smoke detectors, Ionization and Photoelectric detectors. Read on how fire alarm systems work

Have you ever wondered how that little round objects attached to the ceiling ever detect smoke? We see it every day, yet a vast majority of us don’t know how fire alarm systems work. While we’re talking of alarms, do you know that a tiny nuclear reaction takes place within that tiny cylindrical object 24/7? Come along and we’ll take a closer look on how fire alarm systems work.

To date there are two types of smoke detectors, and the most commonly used are the ionization detectors. They are cheap, require little space, and are far more effective than the other type which are the photoelectric detectors.

Ionization Detector

Inside the Ionization detector houses a small amount of Americium-241 and two plates of opposite voltage. The voltage is usually provided by a cell and all are housed in an air flowing metal chamber. The actual body of chamber functions as the negative plate and the positive plate covers the Americium. So what does this element do? The Americium generates alpha particles. These particles ionize the oxygen and nitrogen atoms of the air inside the chamber. The event is simply knocking off electrons in the air. As the electrons are knocked off, the air atom gets positively charged and attracts to the negative plate, while the electron gets attracted to the positive plate. Meanwhile, the electrical circuits within the detector senses if there are no disruptions to the pattern.

Because the chamber is open, air passes through freely and gets ionized. But when smoke enters this Ionization chamber, it disrupts the ionization process and the electrical horn within the unit is sounded.

About Americium-241

This element is radioactive, meaning it produces radiation. But the amount within the Ionization Detector is considerably small that the radiation it produces won’t pose harmful effects. Plus, the radiation emitted is mostly alpha radiation which has the penetration factor of only a few centimeters. Several inches of air completely blocks it; a paper can effectively block it. Being housed in a metal cylinder would surely pose no harm. Still, discarded Ionization Detectors should be disposed properly. After all, it is still a radioactive element.

Photoelectric Detectors
Photoelectric detectors aren’t used as largely because they aren’t that sensitive as most require a substantial amount of smoke to go off. Photoelectric detectors consist of two channels, one is to emit light and the other detects it. If smoke particles are present in the air, this will interfere with the signal and the alarms goes off.

Most fire alarm systems are wired together so if one gets an alarm, all fire systems goes off. Some are even wired together with a water shower that automatically goes off in case of fire.

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