Fire safety at home - Smoke Alarms!

By providing an early warning in the event of fire, a working smoke alarm can enable you and your family sufficient time to reach safety in the event of a fire.
Russ Porteous
CEO, Firewize
01 Aug, 2018

Many people neglect to install smoke alarms despite their life-saving potential and low cost. Even those who do have smoke alarms often take them for granted forgetting that they need attention to ensure they continue to work correctly.

There are two types of smoke alarms available today:


When smoke enters a photo-electric alarm, light from a pulsating light source in reflected off the smoke particles onto a light sensor, triggering the alarm.

Editors note:
I have multiple wireless interconnected photo-electric smoke alarms installed in my two storey family home. When an alarm occurs on any one smoke alarm, all of the warning sounders in all other smoke alarms are activated simultaneously.


When smoke enters an Ionization alarm, ionized air molecules attach to the smoke particles and reduce the ionizing current, triggering the alarm. Ionisation smoke alarms are most commonly used in homes.

While photoelectric smoke alarms generally respond faster to smoldering smoke conditions and ionization smoke alarms generally respond faster to flaming fire conditions, both types provide adequate protection against fire. Combination smoke alarms featuring both photoelectric and ionization technology are also available at hardware, department and home improvement stores.

Smoke Alarm Installation

In many countries, it is now mandatory to install smoke alarms. In Australia, home owners are legally required to install 'hard-wired' smoke alarms. These smoke alarms have been approved and carry the relevant Australian Standards approvals. Hard wired smoke alarms should be installed by a licensed electrician.

Recommended Locations for Smoke Alarms

Install at least one smoke alarm on each floor of the house or residence and outside all sleeping areas. Some fire safety advocates recommend installing smoke alarms inside each sleeping area if sleeping with the door closed.

  • Ideally locate near centre of room on ceiling but at least 300mm (12") from any light fixture and 300mm away from any wall.
  • On peaked ceilings install at least 900mm (36") from the highest point and at least 300mm (12") from any light fitting.
  • Install one in every room, including occupied attics, but not in kitchens/bath rooms/shower rooms/boiler rooms/garages.


Locations to be Avoided for Smoke Alarms

  • Within 3m of a steam source e.g. kitchen/bath room or garage.
  • In locations where temperature may fall below 5°C, or rise above 45°C.
  • In very dusty/dirty/insect laden areas.
  • Within 1.5m of light fittings.
  • Any location where the free flow of smoke to the alarm could be interrupted (e.g. next/above a door/air vent/heater/air-con unit).
  • Areas where routine maintenance or operating hush/test button is difficult (e.g. top of stairwells).

What if my Smoke Alarm Operates?

If a smoke alarms warning alarm sounds, '''don't panic'''. Stay close to the floor and get out of the building. Before opening any doors, check the temperature. If the door feels hot to the touch, don't open it. Use an alternate exit.

Smoke Alarm Maintenance

Testing your smoke alarm

Smoke alarms most often fail because of missing, dead or disconnected batteries. So a smoke alarm that's not working is useless and provides a false sense of security. Once a week, test the alarm by pushing the test button with a broom handle to ensure it beeps. Note: Most smoke alarms contain 9 volt alkaline battery however check your manufacturers specification for more information.

Clean your smoke alarms

Clean your smoke alarms regularly with the fine nozzle of your vacuum cleaner to clear away any dust that may prevent the alarm from working properly.

Change your smoke alarm battery

Change the alarms battery if the battery signal begins (a beep at approximately one minute intervals). So that the battery does not go flat, its recommend that you change your smoke alarm batteries each year. A good time is the end of daylight saving in late March as winter is approaching.

Don't allow anyone to disconnect or "borrow" the batteries from your smoke alarms. A smoke alarm can't work unless it's connected to a power source.

Common causes of failure

Smoke alarms are important life safety devices and as such must be maintained in operating condition at all times. Smoke alarms generally become inoperative when the power source (either battery or AC power supply) is disconnected. Disconnected power supply, missing batteries, dead batteries and improperly installed batteries are the most common reasons for smoke alarm failure during a fire emergency.

CAUTION! Radioactivity

Ionisation smoke alarms contain small traces of Americium 241, a radioactive material. This substance requires the smoke alarm to be returned to the manufacturer or the Department of Health for disposal. Do not dispose of it in any other way.

'''DO NOT attempt to fix smoke alarms''', they are inexpensive and can be replaced at a minimal cost.

Limitations of Smoke Alarms

Warning! Alarms are devices that can provide early warning of possible fires at a reasonable cost; however, alarms have sensing limitations.

  • Photo-electric  (Photo-Optical) smoke alarms sense slow smouldering fires better than flaming fires. Home fires develop in different ways and are often unpredictable.
  • Ionisation - Ionisation type alarms offer a broad range of fire sensing capability but are better at detecting fast flaming fires than slow smouldering fires.

Loose batteries, where fitted must be of the specified type, in good condition and installed properly.

Smoke alarms cannot provide an alarm if smoke does not reach the unit. Therefore, smoke alarms may not sense fires starting in chimneys, walls, on roofs, on the other side of a closed door or on a different floor. If the alarm is located outside the bedroom or on a different floor, it may not wake up a sound sleeper. The use of alcohol or drugs may also impair ones ability to hear the alarm. For maximum protection a smoke alarm should be installed in each sleeping area on every level of a home. Hearing impaired occupiers should consider fitting additional strobe accessories to give a visual alarm.

Although smoke alarms can help save lives by providing an early warning of a fire, they are not a substitute for an insurance policy. Home owners and occupants should have adequate insurance to protect their property.