[rwky]

10 years, you're lucky, one of mine just started doing it after 4 years, it comes with a 5 year guarantee but of course I don't have the receipt and even if I did I don't have the will to fight for a replacement. I think these new alarms are designed to fail early I've never had one fail before but after checking up on different makes and models they all seem to fail randomly.

[duskwuff]

This is by design, and it's for a good reason. The carbon monoxide sensor chemically degrades over time. Good CO detectors will perform self-tests periodically, and will go into an end-of-life mode when those tests fail, or when the sensor's expected lifetime has expired.

[SAI_Peregrinus]

Yep, and that's a big reason why combined Smoke + CO detectors are a bad idea. The smoke detector side doesn't wear out, the CO detector side does.

The beep patterns for "dead battery" and "detector worn out" are usually different. Generally they're printed somewhere on the unit, in a tiny font that's hard to see bleary-eyed at 3AM when it inevitably starts.

[tlavoie]

Smoke detectors usually have something like a 10-year usable life, and should have a sticker to that effect along with its manufacture date.

I've had a couple that when they aged out, went straight to full-on alarm beeping.

[SAI_Peregrinus]

True, this does depend on the detector type. Photoelectric detectors last pretty much indefinitely, but ionization smoke detectors do age. And you ideally want both, since they detect different sorts of combustion. Also there are smoke detectors you can buy with a 10-year life lithium primary cell, so no need to change batteries. These are perhaps a bit wasteful (the cell isn't replaceable and the rest of the detector could be fine) but also don't require throwing away lots of 9V batteries.

[tlavoie]

Oh, true enough. Or at least, by the time the battery gets low, the whole thing should be replaced anyway. As you say, depending on detector.

[SoftTalker]

I have a plug-in CO detector that's probably 30 years old. Has never given any "end of life" alerts but maybe they didn't have them back then. Guess I should replace it.

[duskwuff]

You definitely should. 30 years is almost certainly beyond the useful life of the sensor.

[fallinghawks]

FWIW some smoke alarms have a manufacture date printed on the side, so a receipt might not be necessary.

[prerok]

But... you have to go to a shop to get the replacement. I suppose you could mail it by yourself to the manufacturer, though I must admit I never tried that. It requires too much effort, contacting manufacturer, describing the problem, etc. Do people do this?

[ChoGGi]

How would you prove it came from a certain store?