Fire and security glossary

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Addressable: A fire alarm system where every device has its own address, so the panel shows exactly which device has operated.
Ah (amp hour): A measure of battery capacity. A battery that can supply 1 amp for 7 hours is 7 Ah.
Anti-panic area: A large open area where people need enough light to see where they are going and find the way to the exits if the lights fail.
ARC (alarm receiving centre): A monitoring centre that receives alarm signals from premises and acts on them.
ATS (alarm transmission system): The link that carries alarm signals from a building to the monitoring centre, such as a phone line, mobile signal or internet connection.
Basic service: The yearly service of a fire extinguisher by a competent person.
Beam detector: A detector that sends a beam of light across a room and raises the alarm when smoke blocks or weakens it. It suits large, high spaces.
BS (British Standard): A standard published by BSI, the British Standards Institution.
Central battery: An emergency lighting system where one battery system feeds many light fittings, instead of a battery in each one.
CIE (control and indicating equipment): The fire alarm control panel.
Class A: A fire in ordinary solid materials such as wood, paper and cloth.
Class B: A fire in flammable liquids such as petrol and paint.
Class C: A fire in flammable gases.
Class D: A fire in metals.
Class F: A fire in cooking oils and fats.
Commissioning: Setting up and testing a new system at handover, to show that it works as designed.
Competent person: Someone with the training, skill and experience to do a job safely and correctly.
Condemned: Taken out of use because it is no longer safe or fit for its job. A condemned extinguisher is withdrawn and not put back into service.
Controller: The unit in an access control system that decides whether to open a door, using what the reader tells it.
Conventional: A fire alarm system where devices are wired in zones. The panel shows which zone has operated, not which device.
Credential: What a person uses to prove who they are to an access control system, such as a card, fob, PIN or phone.
DORI: Detect, Observe, Recognise, Identify: the four main CCTV levels in the 2015 edition of EN 62676-4. The 2025 edition replaced them with seven levels.
EN (European Norm): A standard agreed across Europe. Many British Standards are the European standard with a British cover, such as BS EN 1838.
End-of-line device: A component fitted at the end of a circuit so the panel can monitor the circuit for faults.
Escape route: The way people take to get out of a building in an emergency.
Extended service: A fuller service of a fire extinguisher, done every five years for most types, where the extinguisher is stripped down, checked and refilled.
Fail-safe: A lock that releases when the power is removed.
Fail-secure: A lock that stays locked when the power is removed.
False alarm: An alarm with no real fire, break-in or other emergency behind it.
Field of view: How wide an area a camera can see, given as an angle.
Grade (intruder alarm): A number from 1 to 4 for the level of risk an intruder alarm is designed to resist. A higher number means a more capable intruder.
Hydraulic test: A pressure test using water, to check that an extinguisher body is strong enough for continued use.
IEC (International Electrotechnical Commission): The body that writes international standards for electrical and electronic equipment.
Isolator: A device on a fire alarm loop that cuts off a short-circuited section so the rest of the loop keeps working.
Log book: The record kept with a system of tests, events, faults, false alarms and services.
Loop: A cable that runs from the fire alarm panel through the devices and back to the panel, so it can be fed from both ends.
Luminaire: A light fitting. An emergency luminaire has its own battery or is fed by a central battery.
Lux: A measure of how much light falls on a surface.
Maglock: A lock that holds a door shut with an electromagnet. It releases when the power is removed.
Maintained: An emergency light that is on all the time and stays on when the mains fails.
MCP (manual call point): The break glass unit someone operates to raise the fire alarm.
Multi-sensor: A detector that reads more than one thing, such as smoke and heat, and combines them to decide on an alarm.
Non-maintained: An emergency light that is off until the mains fails, then comes on.
NVR (network video recorder): A recorder that stores video from network cameras.
Operational requirement: A written statement of what each CCTV camera is for, such as spotting movement or identifying a face. The design is checked against it.
PD (published document): Guidance from BSI that is not a full British Standard. PD 6662 is the UK scheme for applying the intruder alarm standards.
Photometric check: A measurement of light levels, to confirm an installation still meets its design.
PIR (passive infrared detector): A detector that senses the heat of a moving person. It is the usual detector in an intruder alarm.
PoE (power over Ethernet): Power supplied to a device through its network cable.
ppm (pixels per metre): How many pixels of a camera image cover one metre of the scene. It measures how much detail a camera captures at a distance.
PSU (power supply unit): The unit that converts mains power to the low voltage a system needs, and usually charges a standby battery.
Rated duration: How long emergency lighting must keep working on its battery. It is 1 hour or 3 hours, depending on the building.
Reader: The unit at a door that reads a card, fob, PIN or phone and passes it to the controller.
Responsible Person: The person in control of the premises, who has the duty to keep fire safety measures working.
REX (request to exit): A button or sensor on the inside of a door that opens it for someone leaving.
Self-contained: An emergency light with its own battery inside the fitting.
Sounder: The unit that gives the audible alarm.
Standby: The normal ready state of a system, with no alarm or fault. Battery standby is the time the batteries keep the system running if the mains fails.
Tamper: A switch or circuit that raises an alarm if someone opens a cover or cuts a cable.
Uniformity: How even the light is. It is the brightest reading divided by the dimmest, so a smaller number is more even.
URN (unique reference number): A reference number that a police force issues to a monitored alarm system so that it can get a police response.
VAD (visual alarm device): A flashing light that shows an alarm to people who cannot hear the sounders.
Variation: A departure from a recommendation in the standard, which is agreed with the client and recorded.
VMS (video management software): The software that shows, records and manages CCTV cameras.
Zone: An area of a building covered by a group of detectors, shown as one area on the fire alarm panel.

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