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I don't have really solid references, but I get the impression
that ionization smoke detectors were designed against an
objective rate of a failure per thirty years, so that a house with
ten might see one fail every three years on average.
But I get the strong impression that
the battery energized type could exhaust its battery and
the warning alarm might pass quickly enough to be unnoticed
if a battery with a strong voltage knee at end of life were
Using rechargeables was also considered unwise, because these
self-discharge rather quickly. Apparently the building code
requirements for such things now often require a hard-wired
connection to a mains supply, with a battery as backup.
For free standing smoke alarms people recommend a ten year
battery, so that the whole device is ditched at that time.
I notice an undercurrent of preference for the IR side scatter
or forward attenuation sensing types - though I'm not sure
this is rational.
A photo sensing, ionization, mains wired hybrid with backup
is supposed to be the gold-standard. As to testing, fire marshals
want more than a press of the test button.
I suppose a snuffed taper would be ideal.
Brian Whatcott Altus OK
At 12:09 PM 9/29/2006, you wrote:
What's the problem? Just a bad battery, or an actual fault in the
system. How are they testing them?
Michael D. Edmiston, Ph.D.
Brian Whatcott Altus OK Eureka!
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