"Bill Browning" wrote in message
news:7fCOd.14294$ya6.298@trndny01...
They say to replace your CO alarms every 5 or 10 years. Why? If they
still
test OK, why replace them?
Bill B.



Easy...and the makers will tellyou this as well.

The sensor loses sensitivity.
They also lose sensitivity if they have been exposed to a large amount of
CO,or even CO2.

The better ones, will simply shut off and will not work after the internal 5
year timer is up. The ones I use, do this. They have an end of life alarm,
and state this clearly in the paperwork.