Multi-sensor alarm

The Technical Handbook – Domestic, published by Scottish Ministers to provide guidance on the Scottish building standards suggests there are 4 main types of fire detector used in dwellings:

• Optical smoke alarms.
• Ionisation smoke alarms.
• Multi-sensor alarms.
• Heat alarms.

Alarms may be hard wired or battery operated, and may be interconnected so that if one detector is triggered, all interconnected alarms sound.

It is important that the right type of fire detector is used for different situations, as false alarms can result in occupants ignoring or disabling fire detection and fire alarm systems.

The most common causes of false alarms are:

• Fumes from cooking.
• Steam from bathrooms, shower rooms and kitchens.
• Tobacco smoke.
• Dust.

Multi-sensor alarms (or multi-criteria alarms) detect more than one fire phenomena, for example optical and heat detection. They may also include other detection capabilities, such as carbon monoxide detection.

A multi-sensor alarm provides early warning of fire and can significantly reduce the number of unwanted false alarms in certain circumstances.

Research by BRE, published in 2014, suggested that replacement of existing detectors in Kings College London with intelligent multi-sensor detectors could reduce false alarms by 69%, and that in the general building stock, the increased use of multi-sensor detectors may avert false alarms from common causes such as cooking fumes, steam and so on. Ref The causes of false fire alarms in buildings.

Intelligent multi-sensor alarms are independently addressed and continuously monitored to verify correct operation. They may also have adjustable sensitivity settings and drift compensation to account for environmental conditions. This can help identify when an alarm is genuine, as opposed to resulting from a maintenance issue or incorrect setting.

In dwellings, multi-sensor alarms are recommended in hallways and stairwells adjacent to bathrooms or shower rooms to reduce the number of unwanted false alarms.

For more information, see the BS 5839 series of standards for fire detection and fire alarm systems for buildings.

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