Smoke alarms buying guide

A smoke alarm could save your life - but does it matter what type you install?
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01 .Smoke alarms

Smoke alarm

In brief

  • Smoke alarms are mandatory in all new homes, and also in all existing homes in NSW, Victoria, Queensland and South Australia.
  • There are two types of smoke alarms - photoelectric and ionisation. If you're unsure which type you have, look on the base. A radiation symbol means it's an ionisation model.
  • Photoelectric smoke alarms are the best for detecting smouldering fires - install at least one of this type.

There can be few more frightening moments than being caught inside a burning house. It’s a situation no-one wants to have to face, but fire brigades fight thousands of fires in buildings every year. Sadly, not everyone gets out safely. To escape a house fire, early warning is vital; that’s why you need a smoke alarm. See our 2010 review of smoke alarms.

Please note: this information was current as of June 2008 but is still a useful guide to today's market.

Fire facts

  • Across Australia between July 1996 and June 2004, 412 people were killed in 366 fatal residential fires. In the cases where it was known whether smoke alarms were installed, 14% had a non-working alarm and 55% had no alarm at all.
  • NSW Fire Brigade research indicates that a third to a half of house fire deaths could be avoided by having a working smoke alarm and a practised escape plan.
  • Most fatal fires happen at night, when people are usually asleep, and they’re most common in winter.
  • The majority of fatal fires are caused by electrical faults, smoking materials such as cigarette ash, or heaters and open fires.
  • Smoke alarms help limit the damage and cost caused by fires, by detecting them earlier.

When you have to install a smoke alarm

Smoke alarms are mandatory in all newly constructed or substantially renovated homes. For new homes, the smoke alarms must be mains-powered (with battery back-ups in case of power failure), so they need to be installed by an electrician. Generally you should have more than one and they should be interconnected so that if one goes off, so do the rest, maximising the chances of alerting everyone in the house. The alarms must comply with the requirements of the Australian Standard AS 3786.

In addition to new homes, smoke alarms are also required in all existing homes in the following states:

For existing homes, the alarms don’t need to be mains-powered; battery-powered models are acceptable, as long as they meet the Australian standard. Check with your local fire brigade; it can give advice about the laws that apply in your state.

Looking for additional security for your home? Check out our security doors buying guide.


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There are two main types of smoke alarm for home use:

Ionisation alarms

  • AlarmThese contain a very small amount of radioactive material (Americium-241), which produces charged particles, or ions, in a test chamber. The alarm monitors the current generated by these ions. When particles given off in a fire enter the test chamber, the electric current changes, setting off the alarm.
  • Basic models can be very cheap ($10 or less).
  • Ionisation models can be prone to nuisance alarms from cooking, so shouldn’t be located near a kitchen.
  • They're best suited to detecting fast-flaming fires that give off little visible smoke. However, most domestic fires tend to be smoky, smouldering fires, and ionisation alarms aren’t as quick at detecting these.
  • While the amount of radioactive material in each alarm is too small to be a health hazard, there is a waste disposal issue. One alarm on its own contains a tiny amount, but thousands of alarms together make a significant amount of radioactive waste. Ionisation alarms therefore have rules about how you must dispose of them — check with your local fire brigade.

Photoelectric alarms

  • These contain a photo cell and a light beam shining away from the cell. When smoke enters the test chamber, some of the light is scattered by the smoke particles and hits the cell, triggering the alarm. Photoelectric alarms are best at detecting smoky and smouldering fires.
  • Dust or insects entering the alarm can cause false alarms, so they have to be cleaned occasionally. Most modern smoke alarms have insect screens to help prevent this problem.

Other types

Other types of alarm available for domestic use include:

  • Carbon monoxide
  • Heat alarms

These are generally for special situations where a photoelectric or ionisation alarm is unsuitable — for example, carbon monoxide alarms are often used overseas to ensure safe operation of central heating systems. Heat alarms are ideal for kitchens. Even if you have one of these types for a special purpose, you should still install a standard smoke alarm as well.

Recent studies show photoelectric smoke alarms could be the best choice for a home.

However, state regulations only specify whether your alarm should be mains or battery-powered. They don’t specify the type of alarm you should install; any Australian Standards-approved ionisation or photoelectric alarm will comply.

Smoke kills

Toxic smoke and fumes are a major risk. In a house fire, it’s the flames that do the structural damage, but smoke is the main danger to people. The majority of deaths in fires come from smoke inhalation/poisoning. Modern homes contain a lot of materials — such as wood, wool, nylon and plastics — which, when burning, give out heavy smoke and toxic fumes such as carbon monoxide and cyanide gas. These materials can smoulder for a long time, putting out a lot of smoke and fumes before they burst into actual flames.

If you’re asleep when the fire starts, you could suffer from smoke inhalation before you wake up; in fact, the combination of toxic smoke and reduced oxygen in the air can make waking up more difficult. So it’s important to have an alarm that rapidly detects smoke.

Why choose photoelectric alarms?

Photoelectric smoke alarms are much faster at detecting this dangerous situation than ionisation alarms. Studies have shown that photoelectric alarms typically respond to smoky fires within about three to five minutes — when the level of smoke is still fairly low and escape is relatively easy. Most ionisation alarms take much longer — up to 20 minutes or more — by which time there’s enough smoke to significantly reduce visibility, making escape much more difficult.

The fast-flaming, relatively smokeless fires that ionisation alarms detect quickly are not as common in most domestic situations. When such a fire starts, it’s usually in the kitchen while someone is there and can do something about it. Even if no one’s there, other nearby material usually catches fire quickly and starts giving out smoke. Photoelectric alarms therefore usually detect fast-flaming fires quickly enough.

Fire industry experts agree

Photoelectric smoke alarms are required by Australian standards and the Building Code of Australia for all sleeping areas and exit paths in commercial buildings such as hotels. Industry experts also generally agree that photoelectric smoke alarms should be the first choice for homes — install at least one. Some fire authorities, and most major smoke alarm manufacturers and distributors, recommend having at least one of each type of smoke alarm to cover different fire situations.

  • Standards Australia or SSL certification ensures the alarm complies with AS 3786.
  • 10-year lithium battery: Some models come with a pre-installed 10-year lithium battery. This eliminates the need to replace the battery every year, since the lithium one will last for the life of the smoke alarm.
  • Test button: This allows you to check the alarm is working. Some models allow you to test by simply shining a torch on the alarm, eliminating the need to climb a ladder or reach up with a broom handle.
  • Hush button: Pressing this button silences false alarms for a few minutes — handy if you’ve burnt the toast and set off the alarm.
  • Battery test: Battery-powered models should monitor their own battery level and warn you when the battery needs changing by beeping every few seconds.
  • Escape light: Some models have a light built in, which turns on when the alarm is activated. This is helpful if there’s a power failure during a fire, as it can guide you out of the house.
  • Interconnection: Most mains-powered and some battery-powered alarms can be connected to each other, so that if one goes off, so do the rest.
  • For people with a hearing problem there are special products available, such ultraloud alarms, strobe lights and vibrating pads for your bed. For details, contact your state’s Deaf Society, Independent Living Centre or fire brigade.

Where to install your smoke alarm

The following is a guide, but check the installation instructions supplied with the alarm.

  • If you have just one alarm, install it between the kitchen/living area and the bedrooms. It should be fairly close to the bedrooms so that you can hear it go off when you're sleeping. If you have a hallway that connects all the bedrooms, that’s a good place to put the alarm.
  • Interconnected alarms in each bedroom, as well as in the living area, can give a higher level of protection. Children and elderly people in particular often aren't reliably woken by an alarm located outside their bedroom.
  • For houses with more than one storey, make sure each storey has at least one alarm. Interconnection is strongly recommended in this case.
  • Avoid putting smoke alarms in the kitchen or bathroom; you'll probably get a lot of nuisance alarms from cooking fumes and steam.
  • If you do install an alarm in the kitchen, a photoelectric or a heat alarm is likely to give fewer false alarms in this location. Make sure it has a hush button.
  • Smoke rises and spreads across the ceiling, filling rooms from top to bottom. Alarms should be on or near the ceiling for earliest warning.
  • Avoid dead-air spaces, such as corners between walls or where the wall and ceiling meet. Put the alarm at least 30 cm away from these areas.
  • If you have to install the alarm on a wall, make sure it’s between 30 and 50 cm below the ceiling. This avoids the dead air space but keeps the alarm high enough to give early warning.

Maintenance tips

  • Don’t paint smoke alarms — the paint could block the air inlets.
  • Test each alarm once a month by pressing its test button (or shining a torch on it, if the model has that feature).
  • Clean and vacuum alarms every six months. This prevents dust build-up, which can block the air inlets or cause nuisance alarms.
  • Change the battery once a year (except for alarms with 10-year lithium batteries). Even if your alarms are mains-powered, they still have a battery for back-up, so they still need to be changed. Do this on a fixed day each year, such as the end of daylight saving, so it’s easier to remember.
  • Replace your smoke alarms every 10 years. Most alarms indicate their expiry date on their base.

More fire safety tips

Fire safety doesn’t end with installing smoke alarms. An alarm can’t put out a fire and it can’t get you out of the house.

  • Escape plan: Have an escape plan and practise it. Make sure everyone in the house knows the drill. Waking up in the middle of the night to a shrieking alarm with the smell of smoke in the air is frightening and disorienting. If you’ve practised your escape plan you’ve got a much better chance of getting out safely. Plan two different ways out of the house, pick a meeting place outside the house (such as at the letterbox), and make sure you’ve planned for helping any children, aged or infirm residents. Don’t deadlock your doors at night — you might be unable to find your keys in the confusion of a fire. Once outside, account for all people in the house and call the fire brigade. Don’t go back inside the burning building.
  • Fire extinguisher and fire blanket: These are useful to have in the kitchen, where fires often start. Read the instructions and know how to use them. However, if you don’t feel confident to fight a fire, don’t risk it. Switch off the burning appliance if possible, get out and call the fire brigade.
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