smoke detectors should be replaced every 10 years

[darkoshi]

The night before last, one of my smoke detectors chirped and woke me up. Then it chirped again. That normally indicates a low battery.

I stood in the hallway to pinpoint which unit it was coming from, but no more chirps. I tested them, and each beeped like it should. I finally removed all their batteries to keep from being woken up again. (I hate doing that, but I need my sleep.) Per my little battery meter, the batteries were all still good. But per my notes on when I last changed batteries, it is quite possible one or more are low by now.

The next day I put the batteries back in and waited all day for another chirp. None of them confessed.

But I read that you should replace smoke detectors every 10 years. Mine are about 20 years old. So now I'm looking to buy replacements.

My existing alarms are not hard-wired, and I don't want to add wiring.
The ones with a built-in 10-year battery sound good; I wouldn't have to keep buying expensive 9V batteries and go through this rigamarole as often.

But then on Reddit I read how many people had these 10-year units fail much sooner, within 2 years or so. Maybe cleaning them by blowing air in them fixes it, or maybe not. Do any of you have experience with these 10-year units, good or bad? What brand?

Smoke detectors also come in 2 types, photo-electric and ionization, or dual. One of my old ones is dual. But so far I didn't find any dual-type ones with the 10-year battery.

Update:
From what I've read, both the "Kidde" and "First Alert" brand 10-year smoke detectors can't be temporarily turned off once they are initially activated. You can deactivate them (at their end of life) but then you can't turn them back on.
So if one starts acting up in the middle of the night, I wouldn't even be able to turn it off temporarily to deal with it the next day.
Also, from what I read, both brands have had problems with units failing after only one or 2 years.

So I'll instead get ones similar to my existing units, where you replace the batteries every so often. At least with them I can remove the batteries like I did the other night.

Comments

[frith]

My previous (Canadian Tire) fire alarm would go off most times that I made toast. That was fine because it meant the fire detection aspect was working. My replacement fire detector doesn't do that, but the battery is fine. That's less than ideal.

[darkoshi]

From what I read, they call that a "nuisance alarm"* and many people purposely disable their detectors (similarly to what I did that night, but more permanently) when it happens a lot.
So the companies have designed them to give fewer false alarms. But also, the ionization type is more likely to have those kind of false alarms than the photoelectric, so maybe your new one is photoelectric.

*I mean, unless your toast actually tends to catch flame.

This page has pretty good info about a third of the way down the page, about photoelectric vs ionization:
NYTimes Wirecutter: The Best Basic Smoke Alarm

[frith]

The Americium-241 in ionization-type smoke detectors has a half life of 432.2 years. I note that the US National Fire Protection Association requires that smoke detectors be replaced ten years after the manufacture date, no reason is given. In California, smoke detectors with replaceable batteries are banned. I find this highly suspect. The only beneficiary of throwing out fully functional household appliances is the manufacturer and the businesses selling them.

[darkoshi]

I've read various reasons. I can't say how accurate they are. But I find it believable that an old alarm may not function at all, or not as quickly as a new one. (I can't even remember the last time any of mine went off except for chirping to tell me their batteries are low).
And I can believe that a difference of a few minutes can be the difference between life and death if there is an actual fire.
So I'd rather err on the side of safety. If you think your old one works better than a new one, you could always keep it and add another.

https://www.consumerreports.org/cro/news/2014/04/when-to-replace-an-older-smoke-alarm/index.htm
The life expectancy of smoke alarms is generally 10 years, after which point their sensors can begin to lose sensitivity. The test button only confirms that the battery, electronics, and alert system are working; it doesn't mean that the smoke sensor is working. To test the sensor, use an aerosol can of smoke alarm test spray that simulates smoke


https://www.familyhandyman.com/article/what-to-know-about-the-new-smoke-alarm-standards/
Next-generation smoke alarms are expected to minimize that annoying screeching when you over-crisp the veggies. They’ll also warn you more quickly about actual fires in your home, thanks to new Underwriters Laboratories (UL) Solutions standards set to take effect on June 30, 2024.

The most notable improvements include better detection of smoldering and burning polyurethane foam (found in mattresses and upholstered furniture) and reducing false alarms from cooking.

“Ultimately, the goal is to prevent people from taking the batteries out of their alarms or removing them as a result of nuisance alarms caused by cooking,” says Susan McKelvey, communications manager for the National Fire Protection Association (NFPA).

“Doing that presents a serious risk, as smoke alarms play a critical role in home fire safety, reducing the risk of dying in a home fire by more than half.”

[frith]

Of course no one has a can of "smoke alarm test spray" on hand. 9_9 Maybe a candle held below the smoke alarm will do. Burning some upholstery foam would be like overkill but at least that would be easier to obtain than a can of simulated smoke.

For an ionization chamber type smoke detector to fail, the contact with the battery would have to corrode to the point that power was no longer going to the detector, at which point pressing the 'test' button would not work either. The alarm goes off when smoke interferes with the ionized particles and cuts the circuit maintained by the radioactive Americium. See https://www.nrc.gov/reading-rm/doc-collections/fact-sheets/smoke-detectors.html If the charged plates in the chamber fail, the alarm would go off because the circuit would be broken. Ergo, I still don't see why smoke detectors need to be replaced every ten years except to keep us buying new ones. I call shenanigans.

I can see the light diode based smoke detectors failing early: either the LED's burn out or get full of dust, but then again, that would cause the alarm to go off.

Only the ten-year-battery models have sure fire built in obsolescence, so much so that if they fail early, you might only find out when your house burns down.