On 12/06/15 20:26, Dave Platt wrote:
My understanding is that the sensor in the CO detectors, being
chemically based, does have a limited lifetime. As of 2009, ANSI/UL
specs require that such alarms begin chirping an "end of lifetime"
signal after 5 years of operation... and a couple of weeks after this,
you can no longer turn off the chirp.
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Perhaps OK for CO detectors , but Americium type smoke detectors have a
very long life ; the ones in my house still work well (tested with
smoke) after 22 years, cleaned with a vacuum cleaner,every 2 years.

Frank GM0CSZ / KN6WH in IO87AT