In article ,
Terry Pinnell wrote:

Can anyone recommend a competitively priced replacement for my CO detector
that has prematurely reached the end of its life please?

It's a 'Model SF350EN', labeled 'British Gas' and its supplier, SF
Detection, want an exorbitant £30 to replace it. Seems daylight robbery to
me. They insist the whole unit needs replacing 'because the sensor dries
out'.

The sticker on mine says 'Replace by January 2012', and given that it was
only installed a couple of years ago I feel short-changed.

I'm tempted to try making one myself. I made a smoke alarm many years ago
which I vaguely recall used a gas sensor as its principal component. Are
CO sensors similar and easily obtained?

If I thought I needed a CO detector - which I don't - I'd not shop for
one based on price. I don't get the logic, there. Aren't you intending
to trust your life to it? Or is this just a junior high school science
experiment?