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Good Question: How do fire alarms ‘smell’ smoke?

How do fire alarms ‘smell’ smoke? (Photo: KUTV)

(KUTV) Scent is a powerful sense, one that, no matter how subtle, can move you.

Imagine: the hint of salt in the ocean's surf. Or can't you just smell the freshly dewed grass that hits you as you hit a chip shot of the rough. Or the smoke that jumps from a crackling fire.

That scent is of particular interest to smoke alarms which sound when they "smell" smoke.

But unlike you and I, there is no nose on these noise machines. So how do they smell smoke?

For the answer, I turned to Lenore Corey with the Sandy City Fire Department.

She says there are two different types of alarms, photoelectric and ionization, which work in different ways.

“With photoelectric there's more of a beam inside and when the smoke goes through that beam, then it makes the alarm go off," she says.

Ionization alarms go off when there is a shift in the ions in the air due to smoke being present, she says.

But as we have all, no doubt, experienced firsthand, both the beam and the air's ions can be interrupted by things besides smoke.

“Spiders can do that. Dust can do that," she said.

Studies show that junk in our air gums up the sensors more than most people may think. The life of a smoke detector is a mere 10 years, Corey says. It’s a fact that nine out of 10 people surveyed by the National Fire Prevention Association didn’t’ know.

And now we know how a smoke alarm smells a fire - and to be wary that their figurative noses have a shelf life.

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