What is the difference between photoelectric smoke alarms and ionisation smoke alarms?

Homeguard 240VAC Photoelectric Smoke Alarm

If you’ve ever shopped around for a smoke alarm, you would know that there are two main types of smoke alarm systems: photoelectric smoke alarms and ionisation smoke alarms. Fire departments and the Fire Protection Association prefer photoelectric smoke alarms; however because the two types of smoke alarms have different benefits and are suitable for different parts of the home, it is important to know the difference.

Photoelectric smoke alarms

Photoelectric smoke alarms detect smoke via the use of photoelectric sensing technology, which uses a light transmission source and a photosensitive receiver. When smoke or dust enters the light path, some light is scattered or absorbed, causing the photosensitive receiver to trigger and sound the alarm.

Benefits of photoelectric smoke alarms

Photoelectric smoke alarms are most efficient at detecting smouldering fires, such as those caused by a cigarette accidentally being left on a sofa. In that situation, the sofa will actually smoulder before it catches fire. With a photoelectric smoke alarm, the alarm will trigger once it detects the smouldering, giving the occupants plenty of warning before a fire actually breaks out.

Where are photoelectric smoke alarms most suitable?

Suitable for living areas and near kitchens, photoelectric smoke alarms are actually the smoke alarm preferred by most fire departments and the Fire Protection Association because they are much faster at detecting smoke.

It is also important to note that Queensland (10 year phase out of Ionisation Smoke Alarms beginning 1 January 2017) and Northern Territory currently have legislation that only allows the use of photoelectric smoke alarms. For more information on the Queensland Smoke Alarm Law, read about it here.

Ionisation smoke alarms

Ionisation smoke alarms detect smoke using ionisation sensing technology, which comprises a manmade radioactive element called Americium 241. This ionises the air around it, and as a result, makes excellent conductivity possible.

With ionisation smoke alarms, current passes through the gaps in the air with ease without triggering the alarm. However, in the event of particles arising from combustion or dust particles, those particles encapsulate the ionising air, causing an increased resistance to conductivity and therefore triggering the alarm.

Benefits of ionisation smoke alarms

Ionisation smoke alarms are most suitable for bedroom areas, as they are most efficient at detecting fast flaming fires, such as curtains that have caught fire. Compared to a photoelectric smoke alarm, an ionisation smoke alarm would trigger more quickly in that situation.

What does Home Safety Store recommend?

Because ionisation smoke alarms and photoelectric smoke alarms function differently and carry different benefits, we at Home Safety Store recommend having both types of smoke alarms in your home, depending on where they are located. This will maximise the detection of any and all types of possible fires that could occur.

In addition, it is important to ensure that any smoke alarm you buy complies with the Australian Standard AS3786. Fire departments and Australian Standards recommend that you change your smoke alarm at least every 10 years – for your safety and complete peace of mind. Also, remember to change your smoke alarm battery every year if you have a 9V battery back up.

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