On 7/31/2020 3:28 PM, Tekkie� wrote:
On Thu, 30 Jul 2020 23:53:00 -0700 (PDT), Mercellus Bohren posted for all of us
to digest...
....

I meant smoke detectors, not fire alarms. I have a couple of smoke detectors and a couple of combo carbon dioxide/smoke detectors and they both started beeping. The two carbon dioxide/smoke detectors are wired together and to power on one circuit. The started beeping and I replaced the backup batteries. Turns out, both of the CO2/smoke detectors had to be replaced, after about 7 years.

That is correct they must be replaced according to the manufacturers specs. The
sensors inside have a finite lifetime.

Looking at current spec sheets it seems more are related to the use of
"tamper-proof" (and hence non-replaceable by design) batteries w/ a
10-yr life.

I've still not found anything that indicates what, specifically is the
failure mode of the device that would otherwise require replacement at
10 year, whether ionization or photoelectric type.

I did discover that apparently a lot of places have now decreed that
ionization-type are not approved as standalone; only in conjunction with
photoelectric type are they allowed by Code in those locales.

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