Security & Fire Protection Systems/Chirping AC fire alarm system


QUESTION: We have a home with five AC connected smoke detectors.  They are FIREX model 120-1182B with a stamped date of 2006 MAY 22.  There is a chirping noise coming from up in the ceiling directly above or near one of the upstairs detectors.  It is NOT coming from the detector itself.  This particular detector also has a red flash every minute or so.  

We tried replacing the battery in that detector.  Didn't solve the problem.  We tried replacing that smoke detector.  Didn't work.  We tried swapping the detector with another one in the house just to see what would happen and the chirping/flashing stayed in the same location and did NOT follow the original detector to the new location.

We read a solution on here that suggested cutting the power, removing the batteries in all detectors, pushing the reset buttons on each detector, replacing the batteries, reconnecting them and then turning the power back on and that didn't work.  

We have resorted to cutting the power to this particular room at night just to get the chirping to stop while we sleep.  We turn the power on the next morning, and the chirping resumes about 30 hours afterwards every single time.

We are at our wits end on what to do.

ANSWER: Hello Andrew, and thanks for your detailed description.

I'd like you to do one more test, and that is simply to take down the detector that's chirping, and put it on the back porch. If you still hear the chirping (and I think you will) in the original location, that will definitively establish that something else is doing the chirping. In a way, you've already figured this out ... but I'd point out that the Firex detectors don't have a remote sounder; they're built into the unit.

It's likely a carbon monoxide detector plugged into a wall outlet. They sound the same, and for some reason, the noise always seems to come from the usual suspect -- the smoke detector.

Let me know what you find -- and if I'm mistaken, we'll explore further.

Best Regards,


---------- FOLLOW-UP ----------


There is indeed a CO detector in the room, and when we press the test button it does indeed make the chirping noise we'd been hearing.  At least three of us all swore the noise was coming from up in the ceiling so we'd never considered that possibility.  I only wish I'd posted this question before we spent so much time and money on new batteries and smoke detectors.

Thanks for the follow-up. I'm glad you found the problem. And don't feel bad -- I think I've had six or seven similar questions over the years, all ending the same way. And if I recall correctly, the first one took me a long time to figure out.

Best Regards,


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Dave Neuweiler


The design and application of burglary and fire systems for homes and businesses. Helping alarm owners understand how their system works. Helping to troubleshoot false alarm problems. Questions about monitoring issues.


Over a quarter century in the industry. Experience in installation, service, and monitoring centers. Training manager for a national protective services company; director of education and training for a national trade organization for for alarm dealers.


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