Ionization vs. photoelectric smoke detectors: What's the differe - Cincinnati News, FOX19-WXIX TV

Ionization vs. photoelectric smoke detectors: What's the difference?

A photoelectric smoke detector. Note the "P" on the back. A photoelectric smoke detector. Note the "P" on the back.

By: University of Cincinnati Journalism Department student Jamie Gregory. University of Cincinnati Electronic Media Division student William Wolkoff contributed.

A 2013 city ordinance requires the owners of rentals in Cincinnati to install and maintain photoelectric smoke detectors outside sleeping quarters of their properties. Another city ordinance requires them to install ionization smoke detectors in the kitchen area. What's the difference between the two types of detectors, and how do they protect you?

“They're both good, but one works better at one thing than the other,” said Capt. Maurice Vassar of the Cincinnati Fire Department, who is assigned to the fire prevention unit.

Photoelectric detectors generally are more responsive to slow-moving, smoldering fires, those that burn without a flame -- like a cigarette butt burning between the cushions of a couch, Vassar said. Because you need the earliest possible warning when you're asleep, photoelectric detectors are recommended outside of sleeping areas, Vassar said.

Ionization detectors are the most common type of alarm. They sense fast-moving, flaming fires. “A flaming fire would be like a kitchen fire… something that flames up quicker,” Vassar said.

Ionization alarms sense smoke by the work of ions (electrically charged particles), whereas photoelectric alarms detect smoke with a beam of light, according to the National Fire Protection Association. You can tell the difference between the two simply by looking at them. If the detector has a “P” on it, it's photoelectric; an “I,” it's ionization. If you see both letters, it's a combination detector, one with both ionization and photoelectric technologies. But that doesn't mean you should install combination detectors near bedrooms.

“So as not to confuse things, we (the city) exclusively want the photoelectric smoke detectors installed outside of sleeping quarters,” Vassar said.

An ionization detector costs about $4, and a photoelectric is around $10. Both are available at stores like Walmart, Target and Home Depot, as well as online. You also can pick up detectors for free at city fire stations, Vassar said. Just make sure you have them installed in your home, he said.

“In the middle of the night, if something happens, the beeping that smoke detector makes can be the difference between life and death,” Vassar said. “So we can't overemphasize the need to make sure that there's a detector in the building you're sleeping in.”

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