Every smoke alarm has the same job: to warn you early enough to get out. How the alarm senses smoke is another matter. Australian homes have two main technologies on their ceilings, photoelectric and ionisation, and in Queensland the difference is about to become a legal one for every home.
How each type senses smoke
A photoelectric alarm aims a light source through a sensing chamber. When smoke particles drift into the chamber, they change the pattern of light reaching the sensor and the alarm sounds.
An ionisation alarm holds a small amount of radioactive material between two electrically charged plates, which keeps a current flowing. Smoke entering the chamber disrupts that current and sets off the alarm.
What each type does better
Photoelectric alarms mainly detect visible smoke. That suits smouldering fires, which is how many home fires begin: burning foam, rubber and the synthetic materials found in furniture and bedding.
Ionisation alarms mainly detect the very small, invisible particles given off by fast flaming fires, such as burning paper, wood or flammable liquids.
AFAC, the national council for fire and emergency services in Australia and New Zealand, sums up the trade-off: photoelectric alarms currently give more effective warning of smouldering fires, while ionisation alarms give earlier warning of fast flaming fires. AFAC adds that a photoelectric alarm installed near a kitchen may be less prone to nuisance alarms than an ionisation alarm.
What the fire services say
AFAC’s position is that no single alarm technology is the best performer in every situation, and that where alarms are placed, and how many alarms a home has, matter more for early warning than the type of sensor. AFAC recommends interconnected alarms in all sleeping areas, living spaces and paths of travel such as hallways and stairways.
What the law says
Rules differ between states and territories, and some now specify the technology. From 1 January 2027, smoke alarms in Queensland homes must be photoelectric and interconnected, and the Queensland Fire Department tells householders to replace any alarm that contains an ionisation sensor. Our Queensland smoke alarm legislation page sets out what a home needs.
Elsewhere, check the current requirements in your state or territory before you buy.
How to tell which type you have
Look at the label on the back of the alarm. A radiation symbol and the name of the radioactive material, americium-241, mean the alarm is an ionisation alarm. While the alarm is in your hand, find the date of manufacture too: Quell recommends replacing a smoke alarm every 10 years.
The amount of radioactive material is very small. The NSW Environment Protection Authority says the radiation dose to householders is very low, and that the benefit of having a smoke alarm vastly outweighs any health risk from the radiation.
Replacing an ionisation alarm
In Queensland, an alarm with an ionisation sensor needs replacing before 1 January 2027, and the replacement must be interconnected and either hard-wired or powered by a non-removable 10-year battery. Everywhere, replace any smoke alarm that has reached 10 years from the date of manufacture. When the time comes:
- Where local rules allow, small numbers of old ionisation alarms can go out with the household rubbish. Ten or more alarms are treated differently, so check with your state or territory authority first
- Do not open or dismantle the alarm
- If the old alarm is hard-wired to 240V mains, the replacement needs to be hard-wired too, and fitted by a licensed electrician
Choosing a photoelectric alarm
The Quell smoke alarm range offers photoelectric alarms in four formats: wireless interconnected alarms, hard-wired 240V alarms, alarms with a sealed 10-year battery and 9V battery models.
Our guide on how to choose a smoke alarm walks through the options, and the interconnected smoke alarms page explains how linked alarms work.
Where to buy Quell
Quell smoke alarms are stocked at major retailers right across Australia, including
- Bunnings
- Mitre 10
- Kmart
- Coles
- Woolworths
- BigW
You can pick one up next time you’re already out shopping.
You can also find your nearest retailer by visiting our Stockist page.