This Glossary provides definitions of various terms and phrases used in this guide and in relation to Fire Systems in general.
Addressable system A system in which signals from each detector and/ or call point are individually identified at the control panel.
Analogue system A fire alarm system in which the detectors and sensors give output signals that represent the value of the sensed phenomena. The detectors and sensors themselves do not determine if there is a fire, this is decided by the control equipment. This type of system uses both radial and loop circuits, and in the event of a fire, the actual location of the fire within a zone can determined and indicated by the control equipment.
Aspirating detector A detector system in which a sample of the atmosphere in the protected space is drawn by a fan or pump into a detector which may be remote from the protected space.
Automatic system A system in which the fire alarm can be initiated automatically.
Call point A device for manually operating a fire alarm system.
Central station A permanently manned centre, usually provided by a
commercial organisation, the staff of which, upon receiving a fire alarm signal from a premises notify the fire service.
Control and indicating equipment Equipment, which on receipt of a fire signal, controls the initiation of a fire alarm by activating one or more sounders, alarm indicating equipment, or transmitting a signal to other fire alarm control equipment such as a fire alarm
transmission link.
Conventional system A fire alarm system in which all detectors give the same output signal that represents an alarm of fire. This type of system uses radial circuits in which each spur monitors just one zone. An alarm of ‘fire’ is given by the control equipment whenever it receives a signal from any detector. In this type of system, only the zone in which a fire occurs can be indicated by the control equipment; the actual location of the fire within the zone cannot be determined.
EOL End of line device used for open and short circuit monitoring
of detector and sounder circuits.
Final voltage of a battery The voltage at which the cell manufacturer considers the cells to be fully discharged at the specified current.
Fire alarm transmission link An electrical circuit for transmitting fire alarm signals and fault warnings to a central station or control room.
Fire alarm warning A warning of outbreak of fire in an area of the premises
Fire Systems Glossary
Heat Detector A monitoring device designed to automatically initiate alarm at a fixed temperature, or at a specified rate of rise of temperature, or a combination of both.
HPO High Performance Optical smoke detector.
Lantern-light A construction standing above the surface of a roof and intended to admit light to the space below.
Manual system A system containing no automatic detectors and in which an alarm indication may only be initiated manually.
Mimic diagram Plan of a protected premises showing the layout of the fire alarm system in relation to the compartments or subdivisions of the building.
Monitored wiring Failure of wiring, whether to open circuit or to short circuit, will result in a fault warning and not an alarm indication.
Normal supply The supply from which the fire alarm system is expected to obtain its power. The normal supply is usually derived from the public electricity supply system.
Phased evacuation A system of evacuation in which different parts of the premises are evacuated in a controlled sequence of phases, those parts of the premises expected to be at greatest risk being evacuated first. A phased evacuation will normally require at least a two-stage alarm system.
Protection The definition of this term is dependent on the context in which it is used. Four definitions are applicable:
1. The presence of one or more detector(s) able to initiate actions needed for safety of life or property in the event of a fire.
2. The provision of mechanical protection to prevent damage to system components from impact, abrasion, rodent attack etc.
3. The provision of fire resistance to prevent damage to system components from fire in their vicinity.
4. The provision of electrical protection to prevent
temporary or permanent disruption to the system due to overvoltage, excessive current, high transient or radio-frequency interference, etc.
Search distance The distance which has to be travelled by a searcher within a zone in order to determine visually the position of a fire.
Sector A subdivision of a protected premises normally containing
several zones. A sector may cover more than one building.
Sensor A device capable of being operated automatically to initiate a
fire alarm, for example a detector.
Smoke Particulate and aerosol products of combustion generated by
fire, whether this be of the smouldering or open flame type.
In general the particle diameters range from invisible smoke
Fire Systems Glossary
Smoke detector A monitoring device designed to automatically initiate an alarm when smoke is detect in the air. Three types are available, namely Ionisation Smoke Detector, Photo Optical Smoke Detector and High Performance Optical (HPO) Detector.
The Ionisation type detector contains a small radioactive element which measures the electrical conductivity of the air.
The electrical conductivity of air changes if smoke is present.
The Photo Optical type detector measures the smoke content in the air by transmission or reflectance of light.
The HPO type detector responds to smoke in the same way as the Photo Optical detector, but when there is a rapid rate of rise in temperature, its sensitivity is increased so that it also responds to very small smoke particles just like the Ionisation type detector.
Sounder A device used in fire alarm systems to give an audible fire
alarm warning in the event of a fire.
Standby supply An electricity supply, commonly from a rechargeable battery, which is automatically connected to the fire alarm system when the normal supply fails.
Staged alarm system An alarm system in which two or more stages of alarm can be given within a given area.
Examples of staged alarm systems are a two-stage system capable of giving ‘alert’ or ‘evacuate’ signals, or a three-stage alarm system capable of giving ‘staff alarm’, ‘alert’ or
‘evacuate’ signals. The normal condition under which no alarm is given, is not counted as an alarm stage.
Two-stage alarm system A fire alarm system in which the initial alarm is given only in a restricted part of the premises, with an alert signal being given in the remainder of the premises.
Zone A subdivision of the protected premises such that the
occurrence of a fire within it will be indicated by a fire alarm system separately from an indication of fire in any other subdivision. A zone usually consists of an area protected by several manual call points and/or detectors, and is separately indicated to assist in location of the fire, evacuation of the building and fire-fighting.