These are often the cheapest smoke detectors, so if budget is important, this might be the best one to purchase. They contain a very small amount of radioactive material, held between two electrically charged places, that ionise the air and cause current to flow between the two plates.
These two plates are very sensitive to the small particles of smoke produced by fast flaming e.g. paper, wood. They detect this type of fire before the smoke gets too thick. Ionisation smoke detectors are slightly less sensitive to slow burning and smouldering fires, which tend to give off larger quantities of smoke.
Optical fire detectors are more expensive. They work by aiming a light source into a sensing chamber at an angle away from the sensor. During a fire, smoke will enter the chamber, which then reflects the light onto the light sensor which in turn triggers the alarm. Optical detectors are more effective at detecting larger particles of smoke that start with a long period of smouldering e.g. foam/upholstery, PVC wiring. However, they are less sensitive for fast flaming fires.
Combined Smoke Alarms
These detectors use both the Ionisation and optical methods of detecting fires sourced from slow burning/smouldering fires as well as fast flaming fires. The best of the two technologies are available on the market today.
Battery Powered Smoke Alarms
Battery powered smoke alarms require a change of battery every 12 months. However, some smoke alarms are now sold with a sealed fitted battery which lasts 10 years.
Mains Powered Smoke Alarms
This eliminates the problem of checking and changing the battery each year. Experts suggest that you have a battery backup alarm to be on the safe side.
Combined Smoke and Carbon Monoxide Alarms
These types of alarms combine the two essential alarms into one Optical Smoke Alarms and also Carbon Monoxide detection. It reduces costs and maintenance.
Which Alarms Should I Chose?
Experts advise that each house has a number of different alarms; one to detect fast flames and another for smouldering flames with a combination of battery and power supply. A Carbon Monoxide detector is a must if gas fired central heating is installed in a home. Remember to only purchase alarms and detectors that comply with the BSI standard. Look out for this symbol. If you are in any doubt as to which one is right for you, we suggest contacting your local fire station for more information.