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weezercat · Aug 30, 2006, 06:53 AM

Our smoke/fire detectors went off in the middle of the night--the one downstairs first, then the one upstairs, with no detectable cause. We opened some windows and the shrieking stopped. What could have caused this?

This morning as we sat at the breakfast table, a bright light flashed above our heads. The light over the table was off, and it didn't come from the other kitchen light. It last only a second. What is going on?

RickJ · Aug 30, 2006, 07:19 AM

So did you not smell anything at all when you got up and opened the windows?

The bright light is indeed a mystery but almost certainly not related to the smoke detectors.

Are these smoke detectors hard wired? If so,
1. it's typical that when one goes off so do the others that are hard wired, and
2. one going off for no reason is frequently a sign that it's time to chuck it and plug in a new one.

weezercat · Aug 30, 2006, 10:24 AM

Yes, they are hardwired, I believe, as you plug wires from the detector into a panel in the ceiling. They also have 9-volt batteries.

We smelled nothing when we opened the windows, and the detectors went silent when the windows were opened.

My husband is an alarmist and suspects foul play, which I think is ridiculous.

??

RickJ · Aug 30, 2006, 02:15 PM

Ok: the first one that went off is probably going bad. Take that one to the store for a replacement (look closely at the plug type to be sure you're getting one that will not require rewiring). If you find the same make and model, fine. Get just one. If you can't find the exact make and model, get 2 of them and replace both.

Fr_Chuck · Aug 30, 2006, 02:29 PM

Of course they will go off if and when the battiers get low. And if they are on a hard wired security system, the styem does tests of the system normally at night. ( normal settings on equipment) So if the 9vt were both put in on the same day, it is possible they are both getting low at the same rate. ( not really likely to both go to the low level on the same day but possible)

And of course with any systems, they do require regular maintenance, cleaning and also checks by the monitoring company is always helpful.

I have a wired system, that is monitered, I had a yard full of fire trucks last month when I decided to bug bomb the house and forgot to turn off the fire zone alarms in our home.

captain tony · Sep 22, 2008, 03:40 AM

I agree. Our smoke detectors are hard wired and battery powered however they beep for a long while - days - to alert us that the 9 volts are getting low. I have always replaced them before they ran completely down so I don't know if they would trigger an alarm.

Twice now over six years our detectors have gone off for no reason in the middle of the night and scared the begeezeus out of me and my family. Tomorrow (with the suggestion of the forum) I will clean out all of the detectors and replace batteries - see if that helps. If it happens again I will go on out and purchase a whole new set of detectors. (The alarm ran only for about 30 sec. - maybe less - before stopping.)

ballengerb1 · Sep 22, 2008, 08:51 AM

Tony, this is an old post but your comments are still valid. If you get to that point of removing the old alarms you can temporaily hardwire them one at a time to find the bad one. You can them just replace what's broken.

captain tony · Sep 22, 2008, 08:59 AM

Thanks - great idea :-)

Stratmando · Sep 27, 2008, 08:24 AM

To add to Ballengers, temporily capping interconnect wire will help locate offending detector.
One company that starts with a "B" had problems with their detectors, they knew by the date, but I uncovered another batch and they replace all from the factory.

sbowman1030 · Oct 9, 2008, 01:17 PM

I've been in the security business for over 16 years. My suggestion is to buy a can of compressed air, like the one you use for your keyboard and spray the detectors. Too often the get filled with dust that will cause the detectors to go off.

Stratmando · Oct 9, 2008, 02:50 PM

Have you done any recent Painting, Cleaning with solvents?

bdparker · Sep 8, 2010, 03:58 PM

I have a new 4br home and had all the smoke detectors go off at the same time last night. My son and I were bumping each other in the night investigating for a cause. He being smarter than I, turned on a light switch and the screeching stopped... I'm thinking a power surge in the local area and the lights being turned on took enough surface charge to quiet all at the same time... thoughts? T/Storms were in the area but not on top of us. Could I be on the right track?

cdmalcolm · Nov 15, 2011, 11:30 AM

It is the temperature that is setting it off. I have a hard wired system. If The a/c is on for a long time, it triggers the alarm. Here is why. The house gets pumped with cool air. The cool air in the house gets higher until it reaches the ceiling. Hard wired detectors are open to the ceiling. The house is cooler than the space between the floor. About 50 to 70 degrees cooler. Condensation starts to happen over the sensors. Which triggers the alarms. If you turn off the a/c when it began, the air quickly, after about 2-4 minute, starts to warm up. This makes the temperature difference in the house and the space between the floor about 30-40 degrees. At this point, the cool air drops towards the ground and the warn air from the space between the floor starts funneling in the house, stopping the condensation.