Troubleshooting false smoke detector alarms?

Last night we had two false smoke alarms signaled from the same 3rd floor stairwell sensor. There was definitively no smoke, heat, or other environmental changes in the area.

The sensor is an ESL 12-24V 4W Smoke Detector w/ Heat. It is wired together with a relay (The panel is a DMP XR200L 10-242).

The alarm was professionally installed about 4.5 years ago.

What are the likely causes of such repeat false alarms and how would one go about troubleshooting and verifying them?

What is most likely - faulty sensor? dirty sensor? faulty relay? loose wiring? other?


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First thing I would suspect is a dirty detector.

Take apart the smoke chamber and clean it. They should be cleaned regularly anyway.

You say it was professionally installed but when was the last time you had the system PM'd by a professional? Fire systems, especially in places where people sleep, need to have preventive maintenance performed on a regular basis.

It is a pretty simple procedure and you can often get a reasonable rate if you sign a contract for annual tests. The technician will test the back-up battery, ensure wire integrity, check the sensitivity of the detectors, test and clean them and verify proper operation of all system components to include to notification appliances.

This will help avoid false alarms, but more importantly the system is more likely to work when it is needed and get the people out.

The only thing worse than no protection at all, is protection that doesn't work. Remember, it only takes one night without working protection...

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Just did it -- took apart and cleaned out the optical chamber with compressed air and gently swabbed the LED with a clean fine brush -- I will see what happens.

They come by for a "wellness" visit every year. I also am pretty intimately familiar with most of my system but I have been lax in getting around to taking apart and cleaning our 14 smoke detectors (code required that number!)

You are absolutely right.

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I'll second that - I had one site where the drywall dust stirred up from construction was causing a detector to go off constantly... the construction crew just ripped the thing down... *sigh*

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Matt Ion

- A few possibilities: Dust buildup Drywall dust installed too close to a bathroom door (shower steam) cleaning products or insecticide sprayed close to the detector loose wiring insect(s) in the detector or on the connectors rodents chewing on wiring flaky EOL relay voltage fluctuation faulty detector

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Steven Vaughan

Thanks to everybody for the input. I cleaned out the optical chamber (per the manual) and so far no alarm signal after 36 hours.

Everything else looks good on physical inspection but if the cleaning doesn't hold then I will suspect either the device or the EOL relay since I think I can rule out the other potential causes.

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A faulty EOL Relay would cause a trouble condition rather than an alarm. If cleaning doesn't solve the problem just replace the smoke detector.

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