Yesterday while cooking I set off the smoke detector, no I did not burn anything. They go off when I cook over a high heat. And yesterday once they started going off they would not stop. I ended up having to disconnect them all (they are hard wired with an interconnect) and I replaced them this morning. Aaaaaaaand let me tell you, I had a sleepless night last night knowing there were no detectors installed.
https://www.southernliving.com/how-often-should-you-replace-smoke-detectors-8774122
This is only true for the Americium based smoke detectors. The newer photoelectric cell fire detectors don’t decay like Americium detectors, and as long as you replace the battery it’ll be good for however long it’s internal components (capacitors and whatnot) will last.
Technology Connections has a good video about this subject:
https://youtu.be/DuAeaIcAXtg
The half life for americium 241 is like 450 years. The 10 year replacement has nothing to do with decay. It’s just a non specific safety in case any of the electronics or board etc start to fail. Photoelectric detectors have the same 10 year recommendation as a max.
It’s actually recommend by many organizations (like the NFPA) to replace photoelectric detectors more often than ionization detectors, if anything.
It’s tuned to a specific output and isn’t exactly field adjustable. Certainly it will continue to be radioactive long after you’re dead, but that doesn’t mean it will still be working properly.
I know exactly how they work. I’m a firefighter and a hazmat technician. Plus I work on and repair electronics as a hobby. Your smoke detector failing after 10 or 30 years has zero to do with radioactive decay. It’s from contamination (dust) and sensor degradation. Once the metal plates inside get enough buildup from dust (like smoke dust and regular dust) and contamination from humidity, the charge that’s supposed to be detected between those plates from the ionization stays lower all the time. That means less actual “smoke” is needed to drop it below the threshold. This happens MUCH faster than radioactive decay reducing what it will ionize.
This is anecdotical but I moved into an apartment with a 30 year old ionizing smoke detector, and the failure was it was too sensitive, I assume because there were less electrons being emitted from the radioactive element, any faint smoke caused it to go off. Eventually it got into a state where it would always be in an alert state, and was beeping 100% of the time, which was when the landlord finally replaced it.
My assumption with the 10 year replacement recommendation for Americium based smoke detectors is to replace it before it becomes too sensitive and annoying, because they were worried some people would remove the battery and just live without an active smoke detector.
There’s no radiation drop after just 30 years from americium 241. It has a 450 year half life. After decades electric components start to fail and\or things get dirty. After 30 years of getting smoke in it, there was probably a layer of dust\smoke over where the radiation is at that were blocking some of the radiation all the time, that made it more sensitive.
Same issues will happen with photoelectric detectors. It’s recommended to replace both types after no longer than 10 years. I have no idea where the person you responded to got the information about them not needing replaced as often as ionization detectors. If anything, it’s actually the opposite.
I was about to link to the same video. From what I remember though both types have strength and weaknesses in regards to the type of fire.
Edit: watched it again so ionization smoke detectors are better at detecting active fire, although his conclusion is that the benefit is not as big and overall photoelectric ones are better.
According to the one i just had to replace, combo carbon monoxide detectors need to be replaced. I don’t know how the carbon monoxide part works, but i wonder if it’s a reagent or something.
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