Ionization smoke detectors versus Photo-electric smoke detectors
August 15, 2011barriehol
There is an old adage that says if it happens in America it is only a matter of time before it happens here in the UK. If that holds true it could spell the eventual death knell for Ionization type smoke alarms.
In recent months there has been a groundswell of opinion in the States for the phasing out of Ionization alarms for use in residential homes in favour of Photo-electric smoke detectors.
Visually it is not that easy to distinguish the two types but Ionization alarms, often marked with an “I” on the bottom, detect smoke using an electric charge. The smoke particles interrupt this charge triggering the alarm. The more expensive and less common Photo-electric alarms, marked with a “P” on the base, use a beam of light to detect smoke, and rarely produce false alarms.
The anti Ionisation lobby in the States quotes several studies from as far away as Australia that contend ionization smoke detectors are slower to respond to dangerous smouldering fires than photoelectric smoke detectors. These studies also indicate that as Ionisation smoke detectors are so prone to give off false alarms, for example in response to steam or cooking fumes, that as many as 25% of homeowners disable them with potential tragic consequences for life safety. So successful has the lobby been that several cities and a handful of States across the US have already mandated that only photoelectric smoke alarms be used in houses.
Interestingly when a friend of mine took advantage of a free home fire safety audit by his local Fire and Rescue services they fitted three smoke detectors around the house. In the room adjacent the kitchen is an Optical type alarm that detects active flaming fires more quickly than Photo-electric technology whereas in the living area and on the landings they fitted Photo-electric Alarms which suggests the FRS consider both types have their uses. The key issue and one supported by the device manufacturers are to position them correctly. It makes no sense to fit either type actually within the kitchen area as cooking fumes and even gas flame hobs may generate a false alarm.