Smoke Detectors

May 2nd, 2007 by Gene
 

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This is one sound just about guaranteed to get your attention. Today on Engineering Works, we’ll listen to why you hear it, even before the smoke gets in your eyes.

So you settled down on the couch to watch “Friends” last night and forgot all about that pot roast you put in the oven. And the hot pad you left sitting on the hot stove. Have no fear, the smoke detector’s here, right? You may be wrong.

Many people do not realize that their detector is old and needs to be replaced. Engineers study smoke detector failures by staging full-scale fires in residences and have discovered that ionization detectors can take more than twice as long as photoelectric types to detect smoldering fires, often a delay of 15 minutes or more.

About 90 percent of smoke detectors in homes and on the market sense fire and smoke by using an ionization chamber. These detect flaming fires faster than others, but they just aren’t as quick to detect flameless combustion like smoldering fires.

The typical smoke detector in stores is probably the ionization type, although the labeling won’t necessarily tell you that. Photoelectric detectors will often be labeled as such, sometimes with wording about optical sensing.

If you don’t know how old your smoke detector is, or it’s more than eight years old, replace it. Have both photoelectric and ionization detectors installed or purchase a combination model. Place detectors in every bedroom and hallway. Change the batteries at least twice yearly and test detectors regularly. Or forgetting about that hot pad might become a baptism of fire.

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