FAQ | Smoke Alarms

Question: How often should I test my smoke alarm? 


  • Once a week, test the smoke alarm by pushing and holding the test button until it activates.
  • Every six months vacuum and brush the casing to get rid of dust.
  • Every year change the battery (unless it is a 10 year battery)
  • Every 10 years replace the smoke alarm.


What is the difference between an optical sensor and ionisation sensor on a smoke alarm?


Ionisation sensor smoke alarms are the cheaper and most common type of smoke alarm. It uses a small radioactive source and is very sensitive to small particles of smoke from fast flaming fires like chip pans. It will detect this type of fire at the early stages and before the smoke gets too thick to escape.

Optical Smoke Alarms are slightly more expensive alarm but more effective at detecting larger particles from “slow burning” fires such as smouldering upholstery or PVC wiring. They use infra-red light to detect smoke. They are less prone to false alarms.


How many smoke alarms should I have in my house?


Any rooms where a fire could start should have a smoke alarm. Have a heat alarm in the kitchen and a smoke alarm everywhere else (except the bathroom). The living room is an obvious place, but a lot of people forget about the utility room. For ultimate protection, connected alarms give the best response time as all alarms will sound.


What is the best place to locate my smoke alarm? 


Positioning smoke alarms correctly throughout your home is vital to ensure they provide the maximum detection and respond as quickly as possible in the event of a fire. Every property is different and you should always refer to the manufacturers guide. Below are some basic rules to follow.


  • Smoke alarms should be positioned on the ceiling, as centrally as possible within the room.
  • Positioned at least 30cm from walls, light fittings, or any obstructions. This is to ensure that they are outside of any ‘dead air’ spaces that occur in corners that can affect the performance of your alarm. Figure A
  • There should be a smoke alarm within 3 metres of every bedroom door to ensure audibility
  • Alarms should be positioned between high risk rooms (rooms with heat source and combustible fuel source) and bedrooms
  • Peaked and sloped ceilings - smoke alarms should be positioned a maximum of 60cm vertically down from the apex. Figure B
  • If smoke alarm must be wall mounted and alarm has been manufactured to work on walls - position the alarm where the top of the device is between 15cm and 30cm below the ceiling. Figure C. Position smoke alarm at least 30cm from a perpendicular wall to avoid 'dead air' space. Figure C

  • Beams (where the depth of the beam is less than 10% of the room height) – position the alarm twice the depth of the beam away. For example if beam is 15cm beam deep - position the smoke alarm at least 30cm away from beam. Figure D
  • Beams (where the depth of the beam is more than 10% of the room height) – treat the beam as a wall and fit alarms on both sides of the beam, or if the beam is less than 60cm deep site an alarm on the underside of the beam. Figure E


  • Smoke alarms should not be positioned in bathrooms or too close to a bathroom door as steam/moisture can affect them. 
  • Do not position smoke alarms on the sloped ceiling directly above the stairs. In locations with stairways position alarms on the flat ceilings at the top and bottom of the stairs.

Figure A

Smoke Alarm Ceiling Siting

Figure B

Sloped Ceiling Smoke Alarm Siting

Figure C

 Wall mounted smoke alarm siting

Figure D

 Smoke Alarm Siting with Beam

Figure E 

Smoke Alarm Siting Large Beam