On 6/14/2015 7:56 AM, Rob wrote:
highlandham wrote:
The smoke detector fitted in the corridor next to our kitchen ,after 22
years, still responds to the ionised vapours (invisible and hardly
smelled) from the gas cooker when cooking/frying food.
Whatever the specification I consider the device and 2 others ,fitted
near the bedrooms and utility room still performing as intended.
All are battery operated (PP3-9V) . When batteries nearing end of life
the devices bleep at decreasing time intervals, such that they will be
replaced.

Those are probably still the ones with a radioactive source that are
now illegal to sell for consumer use. In my experience they cause fewer
false alarms than the newer types that use an optical principle and
probably temperature as well.

It has happened here that a newer detector issued a false alarm on a
hot day. I arrived home and heard it beep when arriving (before opening
the door). That is scary!
It was at least 35 degrees C in the house, but to me that is not a reason
for triggering a fire alarm.
It also happened on other occasions, but fortunately only when I was
at home, and during the day.


Are you sure your detector doesn't also have a temperature sensor? Some
do, and if the temperature exceeds a preset value, it will go off. It's
designed into some detectors in case of a virtually smokeless fire. It
doesn't make for a primary sensor, but can be a useful backup one.

Without such a sensor, a properly operating smoke detector should not do
this, whether it is photoelectric or ionization.

The radioactive ones never do that. Indeed they sometimes trigger
when frying food, but to me that is an indication they actually work.
The optical one has never actually detected something. Useless.


This is one reason why ionization detectors are not recommended any more
- too many false alarms. That, plus photoelectric detectors are much
faster at detecting real fires.

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Jerry Stuckle

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