I have NFPA document [can't see on website]detailing sound logic for
the 10 year cycle.
Its down to the MTBF rating.
In UK all smoke alarms have to have their replacement date marked on
product label, which is 11 years from manufacture ie 1 year allowed
for shipping/storage etc.

Alarms like most electronics are getting more features for lower
prices year on year, so replacement makes sense.

Bear in mind too majority of householders never carry out any alarm
maintenance as detailed in manuls.
Causes alarms to become over sensitive ie go off for no apparent
reason,
which p***s off householder, who may well then disconnect from AC
power/remove battery.

On CO ALarms most CO cells have max life of 6 to 7 years and many will
shut down via in built firmware.

AGain research shows they do not operate within the UL or British
Standard parameters, ie start to drift & become less sensitive.

"George E. Cawthon" wrote in message ...
wrote:
On Fri, 11 Feb 2005 05:06:39 GMT, "George E. Cawthon"
wrote:


wrote:

On Thu, 10 Feb 2005 05:25:23 GMT, "Bill Browning"
wrote:



They say to replace your CO alarms every 5 or 10 years. Why? If they still
test OK, why replace them?
Bill B.



imho:

I was told in my nfpa based training every 10, since a decade passing
brings new 'features' in the new products, and circuitry isn't tested
to last beyond a decade of use.

Might be a UL issue.

hth,

tom @ www.URLBee.com

That sounds almost like an old safety NCO that said a knot
in an electrical cord was bad because the electrons had to
speed around the corners and that made the wire hot.

Apparently your instructors fall into the same category. I
would be very leery of any of their personal descriptions of
how things work.

Some sensors have a limited lifetime. But many old smoke
detectors are based on a light sensor and there is no reason
that the circuit wouldn't last for decades. My original
smoke detector still works after nearly 30 years. I've got


For like 10 bucks, is it worth it? I mean if the smoke detector meant
to be replaced after 10 years(why now some come with 10 year batteries
so you just toss when the battery dies), you might be gambling with
lives.

Just say 10 bucks is cheap.


another 10 year old smoke detector (ionization type) which
is still so sensitive it goes off every time somebody make
toast.




later,

tom @ www.ChopURL.com
Who says it is meant to be replaced after 10 years? Not on
the unit. Not in the instruction manual. It is an ac wired
unit intended for long term use. Give it a test like the
instruction say and if it passes it is ok. Blindly
following some arbitrary rule for replacing the unit is not
only stupid but wasteful of resources. Test the damn thing.