Fire Detector Types Explained

Choosing the right detector for each area is central to a fire alarm system that responds early to real fires while avoiding false alarms. BS 5839 guides selection based on the expected fire and the environment.

The main types

• Optical (photoelectric) smoke detectors — good at detecting the smouldering, smoky fires typical of soft furnishings and general areas. Not suited to kitchens or dusty/steamy areas.
• Heat detectors — respond to a rise in temperature. Suited to kitchens and areas where smoke detectors would false-alarm, though they respond later.
• Multi-sensor detectors — combine smoke and heat sensing (and sometimes more) to improve response and reject false alarms.
• Aspirating smoke detection (ASD) — draws air samples through pipework for very early, sensitive detection in critical or high-value areas.

Matching detector to environment

The environment drives the choice: general offices and corridors typically use optical or multi-sensor detectors; kitchens and plant areas often use heat detectors; server rooms and heritage spaces may justify aspirating detection.

Why it matters

The best system design is undermined by the wrong detector in the wrong place — either missing an early fire or generating false alarms. Correct selection, siting and maintenance keep detection both sensitive and reliable.