How Do Smoke Detectors Work?

The various detection methods and power sources of smoke detectors

We've all heard them go off before — usually when we're daydreaming while making toast — but not everyone knows how smoke detectors actually work. It seems simple: smoke drifts by and an alarm sounds. But not all smoke detectors work the same way, and understanding the differences between them could help you avoid buying the wrong smoke detector.

Different fires, different alarms

If you've ever taken a first aid course or a class in fire prevention and safety, you know that there are actually four different kinds of fires. Just as specific fire extinguishers are used for a Class A or Class D fire, different types of smoke alarms are best at sensing fire or smoke.

A smoke detector can work in one of two ways, ionization or photoelectricity. An ionization smoke detector depends on a small bit of radioactive material that sends an electric current between two electrodes. If smoke disturbs that current, the smoke alarm goes off.

Photoelectric smoke detectors, on the other hand, use invisible light beams to monitor the air. When smoke causes a beam from a photoelectric smoke detector to disperse, you hear alarm bells.

So which method is best? As you'd expect, both smoke detector types have been tested, and while ionization smoke detectors performed well with high-flaming fires, photoelectric smoke detectors did better with very smoky fires. And since most fire-related deaths are caused by smoke inhalation rather than burns, a photoelectric smoke detector is probably the better choice.

Dual-detection smoke detectors

Fortunately, it's no longer necessary to choose one or the other. Dual-detection smoke detectors are available that use both ionization sensors and photoelectric sensors and cost less than buying one of each.

In dual detection smoke detector models, the First Alert dual sensor smoke detector is widely considered to be the best. It comes with a 10-year warranty, and includes many other features such as remote-controlled operation and the ability to distinguish between hazardous and non-hazardous situations, i.e. burning toast versus burning television.

If you already have ionization smoke detectors in your home, we recommend you complement them with photoelectric smoke detectors. Where there's smoke there's fire and vice versa, but with house fires there’s always more of one than the other. Having both systems in your home will give you the best coverage possible.

Other smoke detector considerations

Most smoke detectors are battery powered, though some are wired into a home's electrical system. A dependable power source is going to affect how a smoke detector works, so checking and replacing your smoke detector batteries on a regular basis is absolutely essential.

One other smoke detector consideration that is often overlooked is how children respond to them. Even if a child hears an alarm, the meaning of that alarm may not be clear.

If you're worried about this possibility, consider getting the KidSmart vocal fire alarm. Instead of an alarm, this smoke detector activates a message that you can prerecord instructing your child what to do, possibly saving crucial seconds that could mean the difference between safety and tragedy.

More information on smoke detectors