Security & Fire Protection Systems/Occasional chirps from smoke detector


I have a First Alert 9120B detector, hard wired with battery back-up. I get an occasional 3 chirp from the detector.  This occurs maybe 1x week. 2 Chirps then nothing. The green LED is lit and the red 1 blink 1x min. The detector is about 2 years old

Any ideas

Hello Ed, and thanks for writing.

First, the LED operation you describe is normal. The audible signals are something else. An alarm condition is  series of three beeps, pause, three beeps and so forth.

Nothing in the literature indicates a 3 beep, pause, 2 beep pattern.

While you may have a defective detector, just make sure you have a good backup battery in place, and you can try cleaning the detector by using a can of compressed are (available at office supply stores). Just use the wand and blow air into every available opening.

If that doesn't do the trick, make sure that it's actually the detector making the noise; I've had cases where a carbon monoxide detector in a wall outlet chirped for low battery, and this was mistaken for the smoke detector.

If the problem persists, let me know if this is a single station, or whether you have more than one detector of this type interconnected in your home.

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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