"Brian Gaff" wrote in message
news
I've got a fire alarm older than that and it still goes off when you do
toast in the kitchen downstairs. it alls bleeps when its battery is going
down, usually in the middle of the night.. Its only those with radioactive
sources that wear out I think.

How do the others work?

Photoelectric.
https://en.wikipedia.org/wiki/Smoke_detector

"John Rumm" wrote in message
...
On 02/08/2018 08:18, Harry Bloomfield wrote:

only the none mains version uses a PP3. Mains version uses a none
replaceable lithium. Admit defeat, put it all back and decide to ring
supplier, because it suggests it has a 10 year guarantee.

in most cases the alarm itself is supposed to be replaced after 10 years,
so if they can make the lithium cell last that long, there is not much
point in making it replaceable - it might only encourage people to carry
on using an alarm that has lost sensitivity.


--
Cheers,

John.

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