Fire Safety Glossary

An addressable fire alarm system is a type of fire detection network in which every device — including detectors, call points, and sounders — is assigned a unique electronic address, enabling the fire alarm control panel to identify the exact location of an alarm or fault within a building.

Aspirating smoke detection (ASD) is a high-sensitivity fire detection technology that actively draws air through a pipe network to a central detector, identifying smoke at concentrations far below the threshold of conventional point detectors. Also known as VESDA (Very Early Smoke Detection Apparatus), ASD is used in data centres, heritage buildings, and clean rooms, and must be designed to BS 5839-1.

A conventional fire alarm system groups detectors and manual call points into fixed zones, each wired to the fire alarm control panel. When a device activates, the panel indicates the zone rather than the individual device. Conventional systems suit smaller, simpler buildings; larger or multi-zone premises typically require an addressable fire alarm system to meet the zone-size guidance in BS 5839.

A false alarm, or unwanted fire signal (UWFS), is an activation of a fire alarm system that does not result from a genuine fire. False alarms waste fire and rescue service resources, desensitise occupants to alarm signals, and reduce the effectiveness of the fire safety system. BS 5839-1 requires responsible persons and their engineers to investigate and address recurring false alarms by reviewing detector siting, type selection, and building processes.

A fire alarm control panel (FACP) is the central processing unit of a fire alarm system, receiving signals from detectors and manual call points, triggering sounders, and indicating the zone or device address of an alarm or fault. It must be installed, commissioned, and maintained by a competent engineer in accordance with BS 5839-1:2017, and must be accessible to the fire and rescue service on arrival.

A fire alarm sounder is an audible warning device that activates when the fire alarm control panel receives an alarm signal, alerting occupants to evacuate. Under BS 5839-1, sounders must achieve a minimum 65 dB(A) at any sleeping position, or 5 dB above prevailing background noise, and must be positioned so that no part of the premises is outside their effective range.

A heat detector is an automatic fire detection device that triggers an alarm when ambient temperature exceeds a fixed threshold (fixed-temperature type) or rises faster than a set rate (rate-of-rise type). Heat detectors are used in environments unsuitable for smoke detectors — such as kitchens, garages, and dusty plant rooms — and must be selected and maintained in accordance with BS 5839.

A manual call point (MCP) is a fire alarm device that enables a person to raise the alarm manually by breaking a frangible element or pressing a button. Under BS 5839, call points must be sited at a maximum travel distance of 45 metres on every escape route, and each installed call point must be included in a regular weekly test rotation to confirm operability.

A smoke detector is an automatic fire detection device that senses airborne combustion particles and transmits an alarm signal to the fire alarm control panel. The two principal types are optical (photoelectric) detectors, suited to slow-smouldering fires, and ionisation detectors, suited to fast-flaming fires. Both types must be selected, positioned, and maintained in accordance with BS 5839.