Smoke Detectors

By Jim Nadeau on Electrical, Home And Personal Safety

Combo smoke and carbon detector

First Alert combination Smoke and Carbon Monoxide Alarm

An Electricians Advice On Smoke Detectors

Are your smoke detectors chirping all the time or just going off on random times?  If you have hard wired 120volt with battery back up smoke detectors here are a few things you can do.

Real or False alarm?

I always remember a service call I got of a customers Smoke/CO detector kept going off one night.  They took it down so it would stop going off and went back to bed.  This particular device was right next to the gas stove and I never found out if it was defective or if there was a reason it was going off.  The family fortunately was not affected by carbon monoxide poisoning and I replaced the device because its activation was a mystery.

If your not 100% sure call the fire department first and let them tell you that there is a defective smoke detector.

Chirping Smoke Alarm

If your smoke detectors are chirping every 30-60 seconds it usually means the batteries need to be changed.  If you have a hard to reach smoke detector a Lithium battery can last up to ten years.

I get a lot of service call requests for smoke detectors that activate randomly and usually in the middle of the night.  This usually means a defective device and the toughest problem your electrician will have is finding out which device in your home was the problem.  When there can be up to 12 smoke alarms activating at the same time, at 2am, all you want to do is shut them off!

TIP: If this happens, slow down and try and figure out which one is going off.   On First Alert Smoke detectors, the unit that initiated the alarm will blink rapidly while the other alarm units will remain off. After the alarm has stopped the unit that initiated will also flash red every 45 seconds.

Most electricians will replace all the smoke detectors in the house because by the time they get there it is difficult to figure out which one went off.  By knowing which one went off you can either try fixing/replacing on your own or letting the electrician taking care of it.  Either way your only replacing one unit rather everyone in the house, which can get costly.

Back of smoke

Replacing A Smoke Detector

If your smoke detectors were installed in the last ten years and you feel you are DIY type of person then hold off on calling the electrician.  You may be able to replace your smoke detector without making any electrical connections by following a few simple steps.

  1. Twist unit to the left and pull it down and off the mounting bracket.
  2. Pull the wire harness plug out of the smoke detector.
  3. Locate the model number off the back of the detector.
  4. Go online and search to see if you can still purchase that particular model number and where.
  5. Sometimes you may find a newer version that is still compatible with your detector.  If you purchase a newer version you just want to check that the wiring harness hasn’t changed (90% of the time they have not) if it has you will need a licensed electrician to change the harness.  Please leave the electrical connections up to a Licensed electrician.
  6. Take your new Smoke detector out of the box.
  7. Install the battery.  For hard to reach places I suggest upgrading the battery to a long lasting lithium battery.
  8. Insert the wiring harness to the back of the smoke detector
  9. Gently push the wires back into the electrical  box as you push the smoke detector up.
  10. Turn the smoke detector to the right until the mounting plate catches.


Please remember that when your smoke detectors go off you should always assume the worst.  Never assume it was a false alarm and go back to sleep.  Most homes now have CO detectors tied in with the smoke detectors and your CO detectors will sometimes talk to you and tell you if it’s smoke or CO.  If your not sure call your local fire department and let them take CO readings and make the determination.

Stay safe!

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About the author

Jim Nadeau

Jim Nadeau is a Master Electrician and owns and runs Nadeau Electric LLC established 2007. Nadeau Electric specializes in older homes and light commercial projects. Jim Nadeau uses his 15 years of electrical experience to review the latest electrical tools and advise on any electrical concerns that may arise for the Concord Carpenter Crew.

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