Smoke Detectors

Smoke detectors are the most common type of fire detection, incorporating ionisation and/or optical (scattered or transmitted light) methods of detection. Ionisation detectors respond to different types of smoke, but are best suited to detecting flaming fires. Optical detectors deflect light when smoke enters a chamber causing a response, particularly to large particles of smoke, e.g. in smouldering fires. Light obscuration detectors use the principle that light is obscured by smoke and are often used to monitor large areas (e.g. factories and warehouses).

UK legislation requires that all new homes are equipped with a mains-powered smoke alarm. Smoke alarms may encompass the detection circuitry as well as an alarm sounder and power supply – normally not relying on a separate control panel. These devices may be powered by batteries or by mains electricity and often can be connected together so that when one smoke alarm detects fire, all sounders will sound. However, there are situations where the basic operations of the smoke alarm are insufficient - full systems meeting BS 5445 and 5389 should be used in such cases.

Smoke detectors are classified in a similar way to heat detectors (e.g. see BS EN 54-7: 2001; BS 5445, Part 9; BS 5446 Part 1: 2000 – this last standard is the full specification allowing approval/certification to the British Standard).