VARIOUS DETECTOR TYPES
Smoke and heat alarms are the first line of defence against house fires, but not all smoke or heat alarms are the same. There are basically four different types so it is important that you choose the right one. The appropriate type of smoke detector must be installed to avoid them being disabled because dust or condensation sets them off falsely.
The following guidance explains the pros and cons for the different types of alarm sensor and where to install them.
IONISATION SMOKE ALARMS are very sensitive to smaller particles of smoke which are produced by faster flaming fires. They are most suited for installation on landings; however, it is recommended that optical or multi-sensor alarms are used instead of ionisation type sensors where possible because of their susceptibility to false alarms. They should not be installed in hallways or near kitchens as they are particularly prone to nuisance alarms caused by cooking fumes.
OPTICAL SMOKE ALARMS are best for detecting larger particles of smoke which are caused by slow-burning, smouldering fires before they burst into flames. They are best suited for installation on escape routes and in main circulation areas. They can be installed near kitchens as they are less prone to false alarms from cooking fumes than ionisation sensors. They should not be installed directly in kitchens, garages or near poorly ventilated bathrooms to avoid nuisance alarms from fumes or steam.
HEAT ALARMS are best for detecting an increase in temperature caused by a fire and are insensitive to smoke. Heat alarms are best suited for kitchens, garages, lofts and other areas where there are normally high levels of fumes, smoke or dust.
MULTI-SENSOR ALARMS contain two separate sensors - optical smoke and thermal heat sensors which monitor both signals and use an algorithm of the combined signals to trigger an alarm. They provide a much faster response to most fire types and are less prone to false alarms associated with individual optical or ionisation smoke alarms. They are recommended for installation in main circulation areas, living rooms, escape routes, hallways and bedrooms. While they do contain a thermal heat sensor, they should not be installed directly in kitchens or garages and should still be treated predominantly as smoke alarms.
A combination of the two types of alarm (dual sensor alarm) is recommended for maximum protection from both fast flaming and slow smouldering fires.
Combined smoke and carbon monoxide alarms are also available.
Household smoke and heat alarms can be battery-powered single units or several interlinked mains-powered devices backed up by batteries. Interlinked smoke and heat alarms offer the best protection as they are more likely to operate and alert occupants to a fire. When one alarm sounds, they all sound!
Mains-powered alarms must be installed by a qualified electrician or installation professional.
Smoke and heat alarms have an average life of about 8 to 10 years. They need to be checked periodically, ideally once a week, and the batteries changed when required or at least once a year. Please note that some alarm sensors have fixed rechargeable batteries by the manufacturer which are not replaceable.
Mains powered optical smoke alarm with 9V alkaline battery.
Mains powered heat alarm with 9V alkaline battery.
Mains powered multi-sensor fire alarm with lithium cell back up.
Mains powered multi-sensor heat & CO alarm with lithium cell back up.
Mains powered CO alarm with lithium cell back up.