Top tips for alarm installations

Every year, thousands of people are admitted to A&E due to injuries caused by fire or with suspected carbon monoxide (CO) poisoning.
From these statistics it’s quite simple to see the importance of not only the correct selection of smoke and CO alarms, but also ensuring installation in the correct location.
Jeremy Roberts, Sales Director of SONA, offers advice on what considerations installers should take into account when installing alarms.
What types of alarms are available?
Below is a list of the sensor technology used in most alarms available in the UK.
Smoke alarms

  • Historically are the most popular. While ionisation smoke alarms are very sensitive to small particles of smoke produced by fast flaming fires, such as chip pan fires, they do have a tendency to generate a large number of nuisance alarms, mostly from toasters, which can lead to end users removing the battery or completely removing the smoke alarm.


  • Are more responsive to fires that begin with a long period of smouldering, such as sofa fires caused from cigarettes, and are less likely to cause nuisance alarms. However, they can be less sensitive to fast-flaming fires that initially generate lots of heat but limited plumes of smoke.


  • This technology is becoming increasingly popular and is used by more than 90 per cent of UK Fire & Rescue Services. Multi-sensor combines optical sensing with thermal enhancement, also known as Thermoptek Multi-sensor, for detection of fast flaming and slow smouldering fires in a single alarm. The alarm constantly monitors for temperature change within the room and if a sudden rise of temperature is detected the sensitivity of the alarm is adjusted and provides a significantly faster reaction to both fire types.

Carbon Monoxide alarms
Electrochemical Carbon monoxide sensing with an audible alarm indication:

  • Electrochemical technology is an accurate and proven method of sensing carbon monoxide. Our patented sensor protects against leakage – the most common failure of other sensors and each sensor is individually tested during production. All SONA CO alarms use sensors produced by our own group company – PACE SENSORS. Each carbon monoxide alarm is 100% tested and calibrated using carbon monoxide during the manufacturing process. 

Alarm location
Smoke alarms:

  • A smoke alarm should be installed inside every bedroom within a property, outside each sleeping area and on every level of the home, including the basement if applicable
  • Smoke alarms installed in the basement should be installed on the ceiling at the bottom of the stairs leading to the next level.
  • On levels without bedrooms, alarms should be installed in the living room or near the stairway to the upper level, or in both locations.

Do not install smoke alarms:

  • Near appliances or areas where combustion can occur such as kitchens, near fires or hot water heaters
  • In areas where condensation can occur such as bathrooms or areas near dishwashers or washing machines. Ensure a distance of at least ten feet is maintained between these areas and the smoke alarm location
  • Near heating and cooling vents as the air could blow smoke away from the detector, minimising the effect of the alarm.

Carbon Monoxide alarms

  • A CO alarm should be placed in rooms with fuel burning appliances, such as boilers in kitchens and fuel burning fires in the lounge
  • CO alarms can be placed on a table or shelf. If the alarm is to be fixed to a wall, then ensure it is positioned at head height so its inline with your breathing level.
  • Portable CO alarms should be placed in the rooms that residents spend the most time in, such as a lounge or bedroom, or transported from room to room

Do not install CO alarms:

  • In a cupboard, behind furniture, near an outside door or ventilation (i.e. extractor fans, windows etc.)
  • Directly next to fuel burning appliances, such as fires or boilers. The alarm should be between 1-3 metres away from these appliances.
  • Do not place an alarm in areas of high condensation and steam, such as showers or near kettles

Location of alarms
The positioning of alarms is vitally important in order to ensure effective detection in the event of a fire or CO incident. It is the responsibility of the installer to make sure the alarm locations comply with any applicable building regulations, but below is a basic guide to follow.
Smoke alarms:
Flat ceiling:

  • Site at least 300mm from walls
  • Site at least 300mm from any light fittings
  • Site as centrally as possibly

Flat ceilings with beams:

  • Site at least twice the depth of the beam away. E.g. 150mm beam depth, site the alarm at least 300mm away from the beam
  • If the depth of the beam is greater than ten per cent of the ceiling height, the beam should be treated as a wall (alarms need to be on either side of the beam)

Pitched roof:

  • Site at no more than 600mm vertically below apex

Wall mounted:

  • The top of the detection element is between 150mm and 300mm below the ceiling
  • Site at least 300mm from a perpendicular wall

Carbon Monoxide alarms (when there is an appliance fitted):
Ceiling mounted:

  • Site at least 300mm from walls
  • Site at least 300mm from any light fittings
  • Site between 1 – 3 metres from a fuel burning appliance
  • If the room has a partition, site the alarm on the side of the room where the appliance is located

Wall mounted (in a bedroom):

  • Site at least 150mm from ceiling
  • Site at least 300mm from a perpendicular wall
  • Site between 1 – 3 metres from a fuel burning appliance

Wall mounted (in a room where there is no appliance fitted):

  • Site at the breathing height of occupants (bed or seated height)

Carbon monoxide alarms should be installed in any room at potential risk from CO gas, such as those with a flue hidden in voids. It’s important to remember that deaths have occurred from CO gas leaking in from a neighbouring property.
Since October 2015, it is the legal responsibility of private landlords to install CO alarms in rented property in England. New guidance in Scotland since December 2015 requires CO alarms to be installed in private rented properties to provide warning if CO gas is present in a concentration that is hazardous to health.
Buying and fitting alarms, and ensuring they are carefully and properly maintained, could provide precious extra minutes in which to escape a serious fire or CO incident. With the important role that smoke and CO alarms play in saving lives, it is vitally important installers have a good understanding of not only what alarm technologies are available, but also the ideal location of each alarm to offer the most effective levels of protection.
For more information on SONA please call 0800 171 2009 or visit