Bubblecar said:
I had one professionally installed recently. Brooks brand (made in Ireland, of all places) with a 10 year lithium battery and 5 year guarantee, so presumably pretty damn good.
This is a photoelectric alarm which is apparently more reliable than the ionization alarms:
Performance differences Photoelectric smoke detectors respond faster (typically 30 minutes or more) to fire in its early, smouldering stage (before it breaks into flame). The smoke from the smouldering stage of a fire is typically made up of large combustion particles — between 0.3 and 10.0 microns. Ionization smoke detectors respond faster (typically 30-60 seconds) in the flaming stage of a fire. The smoke from the flaming stage of a fire is typically made up of microscopic combustion particles — between 0.01 and 0.3 microns. Also, ionization detectors are weaker in high air-flow environments, and because of this, the photoelectric smoke detector is more reliable for detecting smoke in both the smoldering and flaming stages of a fire.
In June, 2006 the Australasian Fire & Emergency Service Authorities Council, the peak representative body for all Australian and New Zealand Fire Departments stated, “Ionization smoke alarms may not operate in time to alert occupants early enough to escape from smouldering fires.”
In December, 2011 the Volunteer Fire Fighter’s Association of Australia published a World Fire Safety Foundation report, ‘Ionization Smoke Alarms are DEADLY”, citing research outlining performance differences between ionization and photoelectric technology.
According to fire tests conformant to EN 54, the CO2 cloud from open fire can usually be detected before particulate.
Due to the varying levels of detection capabilities between detector types, manufacturers have designed multi-criteria devices which cross-reference the separate signals to both rule out false alarms and improve response times to real fires. Examples include Photo/heat, photo/CO, and even CO/photo/heat/IR.
http://en.wikipedia.org/wiki/Smoke_detector#Performance_differences