Old hard wired smoke alarm - why is it randomly going off?

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Old 02-21-17, 05:45 AM
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Old hard wired smoke alarm - why is it randomly going off?

Hi,
I've an old hard wired smoke alarm system (looks to be original. House was built early 90s). For some reason it's started going off randomly in short bursts.
It's a very piercing claxon alarm. Doesn't stay on more than a second or two. Woke us all from sleep.
No lights flashing or other indicators that I can see. No beep messages. Just the thing going off for a second or two with no pattern I've noticed.
I can't figure out what's setting it off or why it's a few bursts and nothing else. There's a fully functional modern (battery) unit literally next to it and it's not doing anything at all.
I've pressed the "test" button on both units and both seem to be working fine.
There's no source of burning anything in the house that might be setting off smoke, and it doesn't have a battery to change, so I'm stumped what to do.
Anyone have any ideas what it might be and what I might do about it?

Thanks.
 
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Old 02-21-17, 05:56 AM
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It's old and out of warranty. Replace it. Smoke, fire and CO alarms are warranted for a limited time. When that time is reached, even if they seem to work, are considered no good.
 
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Old 02-21-17, 06:00 AM
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I agree, past time to replace it! Seems like I read they should be replaced every 10 yrs.
 
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Old 02-21-17, 10:31 AM
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That is correct.... smoke detectors every ten years and CO are usually every seven years.
 
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Old 02-21-17, 10:45 AM
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It was replaced - there's a much newer one right next to it (like literally next to it). Modern one with all the bells and whistles. But since it's hard wired, to remove it I'd have to patch the roof, so I'm just leaving it there.
I'm just wondering what could've set it off this morning, while not setting off the others.
(To clarify, the previous owner upgraded all the hard-wired alarms with modern, battery operated ones but never took out the old ones. So now I have multiple alarms per room).
None of the battery operated ones tweaked, and only the one hard-wired alarm went off. Sounded off twice - the alarm sounding for maybe 3-4 seconds.
 
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Old 02-21-17, 07:18 PM
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No, you can just replace it with a new hardwired smoke alarm. It's a simple replacement. The new one will have a battery backup.

The device is failing because the mildly radioactive sensing element has a half-life and breaks down. Some become less sensitive, and others become hyper-sensitive.
 
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Old 02-22-17, 06:15 AM
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Some localities require a wired in unit by code. Most likely the original owner left them there because of possible code. If they are not properly functioning you might be in violation of local fire codes. Replace as RonFl suggested. Just battery operated units do not substitute for wired in units.
 
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Old 02-22-17, 06:33 AM
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Ah! Ok. Didn't know about the half life stuff. Thanks. Will go shopping this weekend.
thanks.
 
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Old 02-22-17, 08:58 AM
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Just a little follow-up about replacing them. Use replace all the ones that are wired in with the same type of new ones. Devices from different manufacturers don't always play well together. Don't bother asking how I know this.
 
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Old 02-22-17, 09:15 AM
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Same brand or not, the mounting plates will not be the same. You will need to repaint the ceiling and remount the plate.
 
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Old 02-22-17, 09:17 AM
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I deactivated the old hardwired smoke detector in my house and replaced it with a battery one. Since it would not hook up to the box in the wall and wanting to cover that hole I just cut a piece of plywood [finished to match the wall] and attached it as a cover to the box and screwed the new smoke to that plywood.
 

Last edited by marksr; 02-22-17 at 11:44 AM. Reason: fix typos
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Old 02-22-17, 09:26 AM
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So did I. But I don't think it's code. I believe (at least in my town) that a hard wired unit be operable.
 
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