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Why Does My Smoke Detector Keep Going Off for No Reason?

Smoke and CO Detector Installation

Do you have a smoke detector that sounds an alarm when there’s no smoke or fire? We’re sure that creates a few scary heart-pumping midnight false alarms.

You could change the battery, but that usually stops a fire detector from “chirping” (signalling that the battery needs to be changed). In fact, the City of Phoenix fire code requires that ‘Where smoke alarms are permitted to be solely battery operated they shall be replaced with a UL listed smoke alarm with sealed 10-year lithium battery. Smoke alarm shall not remain in service longer than 10 years from the date of manufacture.’

So what’s the real issue?

There are 2 common causes of this annoying problem:

Dust on the sensors

Ionization smoke detectors can mistake dust for smoke. So if your ionization smoke detector is covered in dust, that’s why it sets off the alarm even if there’s no smoke.

You’ll know if you have an ionization smoke detector if the letter “I” is in the model number or there’s any mention of radioactive material, like Americum-241. You’ll find this information on the back of your smoke detector. Check out the fourth picture down in this blog to see what we’re talking about.

Use an air spray can or a vacuum cleaner’s extension to blow or suck off the dust.

Warning: Doing this will move the dust and can cause the smoke detector to go off again. So be careful if you’re on a ladder and doing this.


Your smoke detector may just be old so chuck it and upgrade to newer better smoke detectors. They’ve come a long way since the last time you bought them. You can either change it yourself or schedule one of our electricians to come out and change one or all of them for you.

We suggest getting a detector that is a combination of a heat detector and a photoelectric smoke detector.

A heat detector sensor detects quick flames like an ionization detector would but without causing false alarms from dust particles.

The photoelectric smoke detector sensor detects smoldering flames that give off lots of smoke, but very few flames.

Learn more about the dangers of ionization-only smoke detectors in NBC’s story Some Smoke Detectors May Not Go Off In Time.

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