Or maybe it’s just the smoke detector manufacturers?
At my wife’s request, I’ve gotten around to looking at the smoke detectors in my house. How many do we have (three), where are they (one on each level), do they work (eh, mostly yes). It’s something that one does, from time to time, as a responsible adult.
This is when I found out that the modern recommendation, repeated everywhere, is to toss out any smoke detector that’s ten years old or more. Or maybe seven years old, depending on the source.
Why? Well, maybe (fill-in-something-plausible-sounding here). And if that happened, the smoke detector wouldn’t work.
You wouldn’t want to take a risk of that, would you?
Anyway, this was a new one on me. You’re supposed to toss out all your smoke detectors once a decade, and buy new.
Really?
That’s what they say.
From the radar detector detector department.
I was underwhelmed by the thought of tossing perfectly functioning devices in the trash. That said:
1) I realize some home-gas sensors do wear out, most notably, the sensors in home CO detectors. But this is the first I’d heard that (e.g.) the photoelectric sensors in smoke detectors wear out over time.
2) I realize that I’m not testing the actual smoke sensor when I hit the “test” button on a smoke detector. All that does is test whether the battery is still alive and the noise-making electronics still work.
But after pricing out new smoke detectors, I decided that it was less work and ultimately cheaper and easier to buy a can of, in effect, smoke detector detector stuff. Unlike hitting the “test” button, this stuff does test the actual smoke sensor in the smoke detector.
I can now attest that this stuff definitely works. Aim at the smoke detector, give it a one or two second spritz, and wait to see if the smoke detector will go off. A few spritzes later, and I know that all the freshly-re-batteried smoke detectors in my home work. Despite their advanced ages.
When all is said and done, it’s just a whole lot easier to test the ones I already own, than to settle on and buy/install new ones. Plus, the can is probably going to last for decades.
Net present value of batteries.
The last time I bought smoke detectors was sometime around 2008. This, judging by what’s hanging on my ceilings and walls now. Per today’s testing, all three of those elderly smoke detectors — one for each level of the house — work just fine.
Assuming I change the batteries yearly (twice-a-year is recommended but seems like overkill to me), I’ll spend about $15 per detector, over the next decade, replacing the batteries in those smoke detectors.
Interestingly, for $20, I can now buy a 10-year disposable smoke detector. This uses a long-life lithium-ion battery. In theory, I can mount it today, and it will function for the next decade with no attention from me. At the end of which time, It’ll let me know it’s done, and I should recycle it. And buy a new one.
My point is that keeping my existing smoke detectors running for the next decade costs just about as much as replacing them with new 10-year disposable sealed lithium-ion units. That’s with an annual 9V alkaline battery replacement schedule for those old units, instead of the recommended twice-yearly 9V battery replacement.
Finally, FWIW, here’s what set off my bullshit detector on this entire subject: One of the arguments I read for tossing ionization-type smoke detectors every decade is that the ionizing radiation source fades over time. Which is true, and yet, irrelevant. Americium, the radioactive stuff in ionization-type smoke detectors, has a half life of over 432 years (reference). Assuming I did the math right, the radioactive source in a 10-year-old ionization-type smoke detector will have lost just 1.6% of its original strength. (That matches what the reference just above says, which is a 3% decline after 19 years). When somebody tells you that you need to replace your smoke detector because the radiation source fades over time, my suggestion is to spray them with CRC Smoke Test until they stop talking nonsense. There may be some unnamed part that fails over time in ionization-type smoke detectors, but it isn’t the alpha-particle source.
Conclusion
FWIW, my three existing 20-year-old photoelectric smoke detectors work fine. That’s about what I expected.
That said, it’s really six-of-one, half-dozen-of-the-other replacing them with new disposable 10-year units. I can throw out ten 9V batteries per decade, or one smoke detector per decade, for roughly the same price. (N.B. Three alkaline 9V batteries weighs about the same as one smoke detector, or 130 grams. So I end up tossing out more total mass if I keep the old smoke detectors.)
For now, I’m going to keep the ones I already own, at least until my can of smoke-detector tester runs out.
