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Choosing Alarm Sensor Types

Which alarm sensor goes where?

Fire alarms have different sensors to detect different fire types. Some alarm sensors react to heat and some to the physical smoke created by a fire. By fitting the right type of alarm sensor you will avoid nuisance alarms and get the best protection.

Here is our guide to choosing the right alarm for 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 top house image shows a layout using multi-sensor fire alarms and the bottom house image shows single sensor alarms.

Layout using Multi-Sensor fire alarms

Layout using single sensor fire alarms




Contains optical and heat sensor to detect both smoke and heat, so responds to all fire types from fast flaming to slow smouldering providing the best fire response. As the alarm also intelligently monitors both sensors, the risk of nuisance alarms is virtually eliminated.

Fit Multi-Sensor Alarms in: Hallway, Landing, Living Room, Dining Room, Bedrooms

We recommend the Mains Powered Multi-Sensor Fire Alarm – Ei3024


Optical Sensors


Alarms containing optical sensors use an infra-red beam to detect smoke. They detect smoke from slow, smouldering fires such as electrical fires and are less prone to false alarms from cooking fumes if fitted in the hallway next to kitchens.

Fit Optical Alarms in: Hallway, Landing, Living Room, Dining Room

We recommend the Mains Powered Optical Smoke Alarm – Ei3016

Heat Sensors


Alarms containing heat sensors only detect changes in temperature using a thermistor. The trigger level is set to 58°C degrees. Ideal for kitchens as they will not nuisance alarm from cooking fumes but should not be used in other areas of a property as they will not provide the speed of response required – smoke alarms should be used instead, see above for guidance.

Fit Heat Alarms in: Kitchen, Garage

We recommend the Mains Powered Heat Alarm – Ei3014


Ionisation Sensors


Alarms containing ionisation sensors use a small radioactive source to detect the invisible smoke particles given off by fast-flaming, clean-burning fire such as bedding and clothing. However, they can be prone to false alarms from cooking fumes if fitted near kitchens.

We recommend the Mains Powered Ionisation Alarm – Ei141RC


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.