Choosing Your Smoke Alarm

Which alarm sensor goes where?

There are many types of fire alarms, some with sensors reacting to heat and others react to smoke. We have listed a guide below on the different types of alarm sensors available and which alarm is best suited to each application, helping you to avoid nuisance false alarms and to give you the best possible protection.

Here’s our guide to choosing the right alarm for installation in each area within a property. The two houses below show rooms that are colour coded to show which sensor types are best suited to each area of a typical property. The house on the left shows a layout using multi-sensor fire alarms and the house on the right shows single sensor alarms.


Multi-sensor alarms contain optical and heat sensors to detect both smoke and heat. They typically have the best response to all fire types from fast flaming to slow smouldering. Multi Sensor Alarms also intelligently monitors both sensors, the risk of nuisance alarms is virtually eliminated.

Multi-Sensor smoke alarm installations are most suitable for: Hallway, Landing, Living Room, Dining Room, Bedrooms.

Green Electrical recommends the Mains Powered Multi-Sensor Fire Alarm – Ei3024

Optical Sensors

Optical Smoke Alarms use an infra-red beam to detect smoke. They detect smoke from slow, smouldering fires such as electrical fires.

Optical smoke alarm installations are most suitable for: Hallway, Landing, Living Room, Dining Room.

Green Electrical recommends the Mains Powered Optical Smoke Alarm – Ei3016

Heat Sensors

Ideal for kitchens as they won’t cause nuisance alarms from cooking fumes, heat alarms sensors only detect changes in temperature using a thermistor. Heat Alarms have a trigger level is set to 58°C degrees. Heat Alarms are not recommended to be used in any other areas of a domestic property as they will not provide the speed of response required, as above Smoke alarms should be used.

Fit Heat Alarms in: Kitchen, Garage.

Green Electrical recommends the Mains Powered Heat Alarm – Ei3014

Ionisation Sensors

Smoke alarms containing ionisation sensors use a small radioactive source to detect the invisible smoke particles given off by fast-flaming, clean burning fires such as bedding and clothing. Ionisation alarms shouldn’t be used in or near kitchens as they can be prone to false alarms from cooking fumes.

Fit Ionisation Sensors in: Bedrooms.

Although our preference is to recommend and install multi-sensors and optical alarms, for Mains Powered Ionisation Alarm’s Green Electrical would recommend – Ei161e

Regardless of the sensor type, alarms should be interconnected throughout a property to ensure all alarms sound in the event of an activation, providing audibility for the occupants. By using RadioLINK, alarms can be interconnected wirelessly using Radio Frequency signals to reduce the time and disruption from running cabling between the alarms.

Linked or interconnecting alarms

To meet today’s standards and requirements, many domestic smoke alarm installations requires that the alarms, including heat alarms are interlinked, meaning if one alarm is activated then all the alarms installed on the same circuit are also sounded. It is also possible to retro install an interlinking set up using radio frequency radio bases.

Green Electrical recommends Aico RadioLink + Ei100MF.

RadioLINK+ wireless interconnection technology uses radio frequency (RF) signals to wirelessly link alarms together with added functionality. Interconnecting alarms is vital so that occupants can hear the alarm throughout the property and is required in the British Standard BS 5839-6:2013.

There are many reasons for using wireless interconnection:

  • Eliminates tricky wiring runs
  • Saves time at installation
  • Reduces mess and disruption during installation
  • Saves money
  • Makes it easier to add in new alarms and accessories

The RadioLINK+ module Ei100MRF is compatible with the 160e Series and the Multi-Sensor Fire Alarm, Ei2110e.

Which smoke alarms should I choose and where should they be fitted?

There is a general rule for smoke alarm positioning please see below:

Bedrooms - Optical smoke detectors OR combined optical smoke and heat detector.

Landings - Ionisation smoke alarms OR Combined optical smoke and heat detector.

Kitchen and Garage - Heat alarms