"Brian Gaff" wrote in message
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Well, ionising ones tend to spot invisible things if they change the
conductivity of an ionised area in the sensor, but optical ones presumably
have the band set to attempt to detect most smoke particles. I guess in
the end it depends what is burning. I'd suspect that tiny toast burns
might produce larger particles than something like a smouldering item, but
I've not tested it.
Presumably all must conform to some kind of standard and how can one tell
if smoke is from burned toast or a real fire in the end?

But it is useful to distinguish between steam which can
come from such innocuous sources as the shower or
the vegys being cooked, and something like burnt toast.

And the best ones give an earlier warning of something
that has melted like an electrical cord which hasn’t yet
actually set fire to the curtains or carpet etc too.

"Jim GM4DHJ ..." wrote in message
...
are optical smoke alarms better for less false alarms than ionising
ones...in practice I mean ? .....