How Does a Smoke Detector Work?

Protecting our family and home with smoke detectors started as early as 1901. The importance of an early warning system from fire and smoke continues to be a priority across the United States.

Today the 2 most common types of smoke detectors are photoelectric and ionization. The power source for these detectors can be as simple as a 9-volt battery or as dependable as our home’s electrical current.

As I’m sure you can guess, they each work in completely different ways, but have the same goal in mind. They each want to do their part in helping to keep us safe and save us from disaster. Here’s a brief description of them both.


You guessed it! Photoelectric uses light to sense smoke. A photo beam is used inside the detector in conjunction with a sensor. When smoke enters the detector, it scatters that light. So when that same internal light hits the sensor, it triggers a loud piercing siren we’ve all come to know.

This type of detector is best at detecting fires that produce a lot of smoke, such as a mattress or piece of furniture for example.


Perhaps the most common and affordable detector is the Ionization type. It may be hard to believe, but inside these detectors is an extremely small amount of a radioactive element called americium-241. This material is used in an ionization chamber (similar to an aluminum can) that is a source of ionizing radiation which helps to detect smoke.

Sound confusing? Here’s how it works. The chamber consists of 2 plates along with a power source that produces the voltage and the americium-241 produces the ionizing radiation. This combination produces a small amount of electrical current that the interior electronics recognize.

When smoke enters the ionization chamber, it interferes with the current. This drop in current is what lets the sensor know that a fire could be nearby and sounds the alarm.

Douthit Electrical can discuss any changes or upgrades of your smoke detectors that you may want to consider for your home. We have been providing Charlotte with quality electrical services since 1990. When you need help with your electrical service or installation, check out our money saving coupons and give us a call!

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