I am living in a newly constructed house with hard-wired combo smoke alarm/CO detectors. For the first year we had no real problems, but recently the CO detectors go off every so often which makes the dogs (and us) go crazy. The first few times it happened, it was summer and every window in the house was open. Believe me when I say we have a lot of windows.

Because we seemed to be in no danger with the windows open, we did not call the fire dept at 10:30 pm on a Sunday. I did call them after the fact and they came out and inspected and could not come up with a reason why that would happen when the windows are open.

I called the engineer and the plumber (who installed the heat and HRV system) to ask what they thought, and they had no useful info either—basically now that the house is finished I think they are done with me. The electrician has offered to swap out the combo units for separate ones—putting the smoke alarms on the ceiling where the connections are currently, and putting the CO detectors plugged into an outlet nearer to the floor. Needless to say he is in no hurry to come out and do that with the holidays and a new baby in his family.

So, in the meantime, we have our detectors unattached. I know, not good. After the 2 or 3 times in the summer that they went off, we re-attached them and had no problems until December, when again they went off in the middle of the night. Since then they are all disconnected (except for the one in the basement which so far has been OK). EVERY window is closed in December, so this is more of a concern, and I am not happy about not having either smoke or CO detectors working!

I asked my nearest neighbor, also in a new house (different builder) and he said he has the same problem, but has had all of his disconnected since moving in, several years before me.

Any ideas? Anyone else having the same problem? Who do you call to investigate a problem like this?

This message has been edited. Last edited by: KatyDaly,

I had the same issue with the smoke alarms and was told that a minute spec of dust on the sensors can cause all sorts of issues. Use some spray canned air to clean all the sensor areas. That did it for my smoke alarms.

Also, when they are hardwired it is hard to tell which one is the issue. Generally there is a light that flashes fast on the one that is the issue. Call the manufacturer if you can't tell which one is causing the issue.

This may sound odd, but there could be a source of RFI causing your detectors to go off. But first do blow air through it to see if any dust might be setting off the units. Sources of RFI (radio frequency interception) could be a micro-wave oven or a nearby radio transmitter. Being that your detectors are what we call a "FCC Type 15 Device", RFI is totally possible and if so, the resolution is your problem and not the source. I just wish the manufacturers of these devices would spend another 50c to provide the proper filtering components so this wouldn't happen. Snapping ferrite chokes over the wires to a device intercepting RF might be a solution. You can still buy ferrite chokes from Radio Shack.

Jerry, it costs 50 cents to a buck at manufacture to shield these things so RF interference can't mess them up. next to nothing.

but that's a Chinaman's daily wage. and by the time it plusses-up the profit at every stage of the supply chain, it turns into another five bucks.

in a TV or stereo, that's still nothing, leave out the remote batteries and it's dead even. in a smoke or CO alarm, this one is $12, and this one is $17 with all the features... but this one over here is missing two features and costs $24.

dust on the shelf over those units.

a first step on any little electrical dingus acting funny at random times should be putting snap-over ferrites on every wire you see. twist 5 to 8 coils over the unit before snapping it shut if you have slack.

In this highly development society, everybody wants to live in a safety condition. But now lots of people are still worrying about that their privacy and important information may steal by others by installing or using some kind of equipments. If so there must be some methods to help improve the situation, so people come up with the invention of the Radio Frequency Detector to solve the problem.

This message has been edited. Last edited by: jammerlious,

Katy, thanks for raising this problem and thanks to those who answered with suggestions. We had this problem once at my father's house and couldn't figure out what was wrong. Now I know to check the dust level first.

Interestingly enough, something similar happened when he was wearing an external defibrillator but we couldn't figure out which device was alarming. It wasn't the defibrillator, sounded as if it was from the caller ID phone, but was almost like a "surround sound" with no specific emanation point. Now I'm wondering if it was an RFI issue.

Thanks, guys, for the good suggestions.

curiously, somebody just posted on eHam that they are setting their old CO detectors off. I assume that means that ham radio is a gas.

might be worth getting some of those "interference" chokes... they are two pieces of ferrite ceramic in a snap-together plastic shell... and guide all the wires to and from the CO detector at each unit in the power box through one of those, then clip it shut. a real thorough test could be made by shutting off the power on that circuit, and connecting "Y" spec interference capacitors from Mouser or Digi-Key across the power line white and black, and the "chain alarm" wires separately, that link all the wired detectors together. .05 or .01 would be good values.

if you don't know what the latter part means, you should not fiddle with it. UL and the European safety agencies have certified as safe a type of interference capacitor.. "X" from wire to ground, and "Y" across the power line. it means adding components to the power line, which if done badly is a hazard.