Smoke detection

Well, domestic sensors are ionisation type using some isotope of Americum I believe, and they are cheap. But they will go off at the slightest provocation - like on burning the toast.

But anyway, what is your criterion for better ? Eventually the isotope in ionisation sensors will decay - so they won't last for ever.

I believe, and they are cheap. But they will go off

ionisation sensors will decay - so they won't last

Would you know whether the domestic smoke detectors operate in a cascade way or progressive/variable current with smoke concentration until an externally set threshold is reached? Whether up to some smoke concentration level there is no response but at some critical level there is a cascade response or linear/quadratic function or whatever.

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

Ionization sensors are more sensitive to actively burning fires. IR sensors will sense heat. Photocell sensors are best for smoke. The best commercially available smoke detectors use both ionization and photelectric sensors. They are not as common, and are more expensive than the ionization types.

way

externally

function

A silly project I got no further than ideas stage with. Arguments in the pub on when to switch ventillator / extractors on. Smokers, which of course incliuded the landlord, would say it wasn't smokey and non-smokers would say it was too smokey so perhaps a converted smoke detector with some sort of non-subjective display . Seems a compromise was reached and v/e on at half c*ck all the time except mid-winter when the inlet, (positive pressure, in non-smokers section) was switched off as freezing cold draught.

-- Diverse Devices, Southampton, England electronic hints and repair briefs , schematics/manuals list on

I read in sci.electronics.design that N Cook wrote (in ) about 'Smoke detection', on Mon, 3 Oct 2005:

To measure smoke density you need a blue light source and a blue-sensitive detector. The detector output is inversely proportional to the smoke density (approximately).

selection.

The frequency being the same as sky blue presumably ?