Fire Alarm Terminology: Plain English Guide

Introduction

This page explains common fire alarm terms in plain English.

It is aimed at non-engineers, including service desk staff, estimators, account managers, facilities teams, administrators, trainees and anyone else who needs to understand what engineers, reports, quotes or fire alarm panels are saying.

This page is not a design guide. Fire alarm systems should be designed, installed, commissioned, maintained and modified by competent people in accordance with the relevant standards, including BS 5839-1 for non-domestic premises.

For a simpler overview of what a fire alarm system does, see:

Fire Alarms: Plain English Guide

Note: This page is intentionally detailed and contains a large number of fire alarm terms. If you are looking for a specific word or abbreviation, use Ctrl+F on Windows/Linux or Cmd+F on Mac to search within the page.

For example, you can search for terms such as EOL, quiescent current, MCP, VAD, loop fault, cause and effect, or ARC.

Quick reference

System types and categories

Addressable system

An addressable system can identify individual devices.

For example, instead of only showing “Zone 2 Fire”, the panel may show:

Smoke Detector - Room 2.04 - Second Floor Offices

Addressable systems are common in medium and large buildings because they provide more detailed information and allow more flexible programming.

Conventional system

A conventional system groups devices into zones.

The panel normally shows the affected zone, but not the exact device.

For example:

Fire - Zone 3

Someone may then need to search that zone to find the activated detector or manual call point.

Manual system

A manual system has no automatic fire detectors.

The alarm can only be started manually, normally by someone pressing a manual call point.

In BS 5839-1 category terms, this is usually a Category M system.

Category M

A Category M system is a manual fire alarm system.

It relies on people discovering a fire and raising the alarm by operating manual call points.

Category L system

A Category L system is intended for life safety.

The purpose is to warn people in the building so they can escape or follow the building’s fire procedure.

There are different levels: L1, L2, L3, L4 and L5.

Category L1

A Category L1 system has automatic fire detection throughout the building.

Its purpose is to give the earliest practical warning of fire for life safety.

Category L2

A Category L2 system has automatic detection in defined parts of the building.

It normally includes escape routes and additional areas where early warning is needed because of higher fire risk, higher fire hazard or sleeping risk.

Category L3

A Category L3 system has detection in escape routes and in rooms that open onto escape routes.

The aim is to give warning before escape routes become affected by fire or smoke.

Category L4

A Category L4 system has detection in escape routes only, such as corridors and stairways.

The aim is to warn people if smoke enters escape routes.

Category L5

A Category L5 system is designed for a specific life safety objective.

It may involve detection in only one room, one area, or a particular part of the building where detection is needed for a specific reason.

Examples might include detection used to support a fire engineering solution, operate a fire safety system, or compensate for a specific risk.

Category P system

A Category P system is intended for property protection.

The purpose is to detect fire early enough to reduce damage to the building, contents, business continuity or assets.

There are two main types: P1 and P2.

Category P1

A Category P1 system has automatic fire detection throughout the building for property protection.

The aim is to detect fire as early as reasonably practical so action can be taken quickly.

Category P2

A Category P2 system has automatic fire detection in defined parts of the building for property protection.

It may be used in areas where fire would cause serious damage, business interruption or high financial loss.

Combined category

Some systems have more than one objective.

For example:

The system category should be clearly stated in specifications, certificates and design information.

Main fire alarm equipment

Fire alarm panel

The fire alarm panel is the main control unit for the system.

It receives signals from devices, displays fire and fault information, operates alarms and may trigger other systems.

Also called:

• Control panel
• Fire panel
• Main panel
• CIE

CIE

CIE stands for control and indicating equipment.

This is the formal term for the equipment that receives fire signals, displays information, controls the system and monitors for faults.

In most everyday conversations, people simply call it the fire alarm panel.

Repeat panel

A repeat panel is a secondary display or control point for the fire alarm system.

It may be installed at another entrance, security office, reception desk or management location.

Some repeat panels are display-only. Others allow controls such as silence, reset or evacuate.

Mimic panel

A mimic panel is a visual display that represents the building layout.

It may use lamps or indicators to show which area or zone has activated.

Mimic panels are often used where a simple text display is not enough for quick location of an alarm.

Zone plan

A zone plan is a drawing near the fire alarm panel showing the building layout and fire detection zones.

It helps staff, engineers and firefighters quickly understand where an alarm has occurred.

A zone plan should be clear, accurate and kept up to date.

Fire alarm device

A fire alarm device is a device that gives a warning of fire.

Examples include:

• Sounders
• Visual alarm devices
• Voice sounders

In simple terms, it is the part that warns people.

Initiating device

An initiating device is a device that can start a fire alarm signal.

Examples include:

• Manual call points
• Smoke detectors
• Heat detectors
• Flame detectors
• Input interfaces from other systems

This is common engineering language rather than a term most clients use.

Manual operation

Manual call point

A manual call point is the red break-glass or resettable unit used by a person to raise the fire alarm.

In plain English:

Press it if you discover a fire.

Manual call points are normally positioned on escape routes and near exits so people can raise the alarm while leaving the building.

MCP

MCP stands for manual call point.

Engineers often use the abbreviation MCP in reports, quotes and panel text.

Example:

MCP activated at Ground Floor Exit

This means someone has operated the manual call point at the ground floor exit.

Break glass

Break glass is an older common term for a manual call point.

Modern manual call points often use resettable plastic elements rather than actual glass, but people still commonly call them break glasses.

Resettable element

A resettable element is the part of a manual call point that moves or drops when the call point is operated.

Instead of replacing broken glass, the engineer or responsible person can reset the element using a key.

Automatic fire detectors

Fire detector

A fire detector is a device that automatically monitors for signs of fire and sends a signal to the fire alarm panel.

It may detect smoke, heat, flame, carbon monoxide from fire, or a combination of these.

Automatic fire detection

Automatic fire detection means the system can detect signs of fire without a person pressing a manual call point.

This is usually done using detectors.

Point detector

A point detector detects fire conditions at one fixed point.

Most normal ceiling-mounted smoke and heat detectors are point detectors.

Smoke detector

A smoke detector detects smoke particles in the air.

Smoke detectors are widely used because smoke is often produced early in a fire. They may be unsuitable in areas with steam, dust, cooking fumes or aerosols.

Optical smoke detector

An optical smoke detector is a common type of smoke detector that uses light to detect smoke particles.

It is often suitable for general areas but can be affected by dust, insects, steam or aerosols.

Ionisation smoke detector

An ionisation smoke detector is an older type of smoke detector that responds to certain types of smoke particles.

They are now much less common in new systems due to radiation source controls, disposal issues and changes in detector technology.

Heat detector

A heat detector responds to heat rather than smoke.

It may operate when a set temperature is reached or when the temperature rises quickly.

Heat detectors are often used where smoke detectors would be prone to false alarms, such as kitchens, boiler rooms or dusty areas.

Fixed-temperature heat detector

A fixed-temperature heat detector operates when the temperature reaches a set level.

It does not normally respond to smoke.

Rate-of-rise heat detector

A rate-of-rise heat detector operates when the temperature rises quickly.

It can respond faster than a fixed-temperature detector in some fires, but may be unsuitable in areas where rapid temperature changes are normal.

Multi-sensor detector

A multi-sensor detector uses more than one sensing method.

For example:

• Smoke and heat
• Carbon monoxide and heat
• Smoke, carbon monoxide and heat

Multi-sensor detectors can improve detection and reduce false alarms when correctly selected and configured.

Carbon monoxide fire detector

A carbon monoxide fire detector detects carbon monoxide produced by fire.

This is not the same as a domestic carbon monoxide alarm used for gas appliance safety.

In fire alarm systems, carbon monoxide detection may be used as one way of detecting certain types of fire.

Combustion gas detector

A combustion gas detector detects gases produced by combustion or thermal decomposition.

Carbon monoxide fire detectors are one example.

Flame detector

A flame detector responds to radiation from flames.

These are often used in industrial or higher-risk environments where fast detection of flaming fires is required.

They need careful selection because sunlight, welding, hot works and other sources can affect some detector types.

Optical beam smoke detector

An optical beam smoke detector uses a beam of light to detect smoke across a large open space.

They are often used in warehouses, atriums, sports halls and other areas where normal point detectors may be difficult or unsuitable.

Beam detector

Beam detector is the common short name for an optical beam smoke detector.

Line detector

A line detector detects fire conditions along a line rather than at one fixed point.

Examples include optical beam smoke detectors and linear heat detection.

Linear heat detection

Linear heat detection uses heat-sensitive cable, tube or sensor cable to detect heat along a route.

It is often used for cable trays, conveyors, tunnels, car parks, waste areas and harsh environments.

Aspirating smoke detection

Aspirating smoke detection draws air through pipework to a detector unit.

It samples the air for smoke and can provide very early warning in suitable applications.

Common uses include data centres, high-value rooms, cold stores, high ceilings and areas where normal detector access is difficult.

ASD

ASD stands for aspirating smoke detection.

Some people also use manufacturer names, such as VESDA, to describe these systems, although VESDA is only one brand.

Sampling pipe

A sampling pipe is the pipework used by an aspirating smoke detection system to draw air from the protected area back to the detector.

Sampling hole

A sampling hole is a small hole in aspirating detection pipework where air is drawn in.

The size and location of sampling holes are part of the system design.

Detector head

A detector head is the removable detector unit fitted into a detector base.

People often use “head” to mean the visible detector on the ceiling.

Detector base

A detector base is the part fixed to the ceiling or back box that the detector head plugs into.

On some systems, the base may also contain electronics, sounders, isolators or other functions.

Remote indicator

A remote indicator is a small indicator lamp fitted away from a detector.

It is often used where the detector is hidden, such as above a ceiling, inside a riser, or in a locked room.

It helps people identify which hidden detector has operated.

Alarm warning devices

Sounder

A sounder is a device that makes the fire alarm noise.

Sounders are used to warn people that they need to take action.

Bell

A bell is an older type of audible fire alarm device.

Many older systems used mechanical bells. Modern systems more commonly use electronic sounders, but bells are still found on some sites.

Electronic sounder

An electronic sounder is a modern sounder that produces an electronic alarm tone.

It may have selectable tones and volume settings.

Sounder base

A sounder base is a detector base with a built-in sounder.

It allows a detector and sounder to be installed at the same location.

Wall sounder

A wall sounder is a sounder mounted on a wall rather than on a detector base or ceiling.

Visual alarm device

A visual alarm device, or VAD, is a flashing light used to provide a visual warning of fire.

VADs are used where sound alone may not be suitable, such as noisy areas, accessible toilets, or areas used by Deaf or hard of hearing people.

VAD

VAD stands for visual alarm device.

A normal beacon is not automatically a properly designed VAD. VADs need to be selected and positioned correctly.

VID

VID is often used to mean visual indicating device.

A VID may provide a visual indication, but it is not necessarily designed to provide a full visual alarm warning to occupants in the same way as a VAD.

Beacon

A beacon is a flashing light.

People often call any flashing fire alarm light a beacon, but not every beacon is suitable as a visual alarm device.

Voice sounder

A voice sounder is a fire alarm device that plays a recorded spoken message.

For example:

Fire. Please leave the building by the nearest available exit.

Voice sounders can help provide clearer instructions than a simple tone.

Voice alarm system

A voice alarm system is a sound distribution system that broadcasts speech messages and warning signals in an emergency.

It is related to fire alarm systems, but detailed recommendations for voice alarm systems are covered separately from BS 5839-1.

Alert signal

An alert signal is a warning signal used in staged alarm systems.

It may tell people or staff to prepare, investigate or await further instruction rather than immediately evacuating.

Evacuate signal

An evacuate signal is the signal telling people to evacuate in accordance with the building’s fire procedure.

Staff alarm

A staff alarm is a restricted alarm given to certain staff.

It allows trained staff to investigate before a wider evacuation or before the fire and rescue service is summoned, where this is part of the agreed fire strategy.

Zones and building areas

Fire detection zone

A fire detection zone is an area of the building shown separately by the fire alarm system.

It helps identify where a fire or activation has occurred.

For example:

Fire - Zone 5 - Third Floor East

Alarm zone

An alarm zone is an area where the fire alarm warning can be given separately from other areas.

Detection zones and alarm zones are not the same thing.

Detection zones are about where the fire signal came from.

Alarm zones are about where the warning is given.

Zone

Zone is a general word that can mean a fire detection zone or an alarm zone.

Because this can be confusing, it is better to be specific where possible.

Sector

A sector is a larger subdivision of a premises, normally containing several zones.

It may cover a large part of a building or even more than one building.

Search distance

Search distance is the distance someone may need to travel within a zone to visually find the fire.

It matters because very large or badly arranged zones can make it harder to locate the fire quickly.

Circulation area

A circulation area is an area mainly used for movement through a building.

Examples include corridors, lobbies and stairways.

Escape route

An escape route is the route people use to leave the building or reach a place of safety during a fire.

Fire alarm detection in escape routes is important because smoke or fire affecting escape routes can prevent safe evacuation.

Inner room

An inner room is a room where you can only escape by passing through another room.

This matters because a fire in the access room could affect escape from the inner room.

Access room

An access room is the room that forms the only escape route from an inner room.

Place of relative safety

A place of relative safety is a place where there is no immediate danger from fire, but where danger could develop later.

Place of ultimate safety

A place of ultimate safety is a place where there is no immediate or future danger from fire and smoke.

In simple terms, this normally means safely outside and away from the building.

Wiring, loops and circuits

Circuit

A circuit is a group of fire alarm components supplied from the same control equipment and protected by the same overcurrent or current-limiting arrangement.

In everyday terms, it is a section of wiring and connected equipment forming part of the system.

Loop

A loop is a wiring circuit used on many addressable fire alarm systems.

Devices are connected around the loop and communicate with the fire alarm panel.

A loop may include detectors, call points, sounders, interfaces and isolators, depending on the system.

Radial circuit

A radial circuit is a cable route that goes out from the panel or equipment and ends at the last device.

Many conventional zones and sounder circuits are radial circuits.

Spur

A spur is a branch taken off a main circuit.

Spurs are not commonly permitted on fire alarm detection circuits.

Sounder circuit

A sounder circuit is the wiring that supplies and controls fire alarm sounders.

A fault on a sounder circuit may affect whether people can hear the fire alarm in part of the building.

Zone circuit

A zone circuit is a circuit on a conventional fire alarm system used for devices in a zone.

It normally monitors manual call points and/or detectors in that zone.

Detection circuit

A detection circuit is a circuit used for devices that detect or report fire, such as detectors and manual call points.

Critical signal path

The critical signal path is the path between fire alarm initiation points and the equipment that gives warning or transmits signals.

In plain English:

It is the important route that allows a fire signal to get from the device that detects or reports fire to the equipment that warns people or sends the signal onward.

Short-circuit isolator

A short-circuit isolator limits the effect of a short-circuit fault on a fire alarm transmission path.

On addressable loops, isolators help prevent one short circuit from taking out too much of the system.

They may be separate devices or built into detectors, bases, call points or modules.

Isolator

Isolator can mean two different things:

1. A short-circuit isolator on the fire alarm loop.
2. A mains electrical isolator used to isolate power to equipment.

Context matters.

Loop card

A loop card is an electronic card in the fire alarm panel that controls one or more addressable loops.

If a loop card fails, devices on that loop may stop communicating with the panel.

Network card

A network card is an electronic card used to connect fire alarm panels together on a networked system.

Network

A network is a connection between multiple fire alarm panels or control units.

Networked systems are common on large sites, multi-building sites and complex buildings.

Fire-resisting cable

Fire-resisting cable is cable designed to keep working for a period of time during a fire.

Fire alarm cables are normally fire-resisting because the system needs to support evacuation and fire safety functions during a fire.

Enhanced fire-resisting cable

Enhanced fire-resisting cable is cable with a higher fire survival performance than standard fire-resisting cable.

It may be needed in certain higher-risk or more complex applications, such as systems supporting phased evacuation or evacuation over extended periods.

FP200

FP200 is a commonly used brand name for fire-resistant cable.

People often use “FP200” generically, but it is a product name, not the only type of fire alarm cable.

MICC

MICC stands for mineral insulated copper-clad cable.

It is a very robust fire-resistant cable type used in some fire alarm and life safety installations.

Screen

The screen is the metallic layer in some fire alarm cables.

It can help with electromagnetic compatibility and may also be used as a circuit protective conductor depending on the cable type, design and installation requirements.

Earth fault

An earth fault means part of the fire alarm wiring or equipment is unintentionally connected to earth.

Earth faults can cause unreliable operation and should be investigated.

Open circuit fault

An open circuit fault means a cable path or circuit has been broken.

Examples include a snapped cable, loose terminal, missing device or disconnected wire.

Short circuit fault

A short circuit fault means conductors that should be separate are touching or connected through a low resistance path.

This can stop devices working and may affect part of the system.

High resistance fault

A high resistance fault means a connection exists but is poor.

This can be caused by loose terminals, corrosion, damaged cable or poor joints.

High resistance faults can be difficult to find because the circuit may work intermittently.

Intermittent fault

An intermittent fault appears and disappears.

These can be caused by loose connections, water ingress, vibration, damaged cables, failing devices or temperature changes.

Monitoring, resistors and end-of-line terms

Monitored circuit

A monitored circuit is a circuit where the panel can detect certain faults, such as open circuit or short circuit conditions.

This is important because faults may otherwise remain hidden.

End-of-line resistor

An end-of-line resistor, often shortened to EOL, is a resistor fitted at the end of a monitored circuit.

It allows the panel or interface to see whether the circuit is normal, open circuit, short circuit or activated.

EOL

EOL normally means end-of-line resistor.

In some contexts, it may also be used informally to mean “end of life”, so check the context.

Alarm resistor

An alarm resistor is a resistor used to create a different monitored value when a device operates.

For example, on some input circuits, the normal condition and alarm condition are represented by different resistance values.

Trigger resistor

A trigger resistor is an informal term for an alarm resistor or operated-condition resistor.

It is commonly heard when discussing monitored inputs.

Monitored input

A monitored input is an input circuit that can detect more than one condition.

For example:

• Normal
• Fire
• Fault
• Open circuit
• Short circuit

This is commonly used when connecting sprinkler flow switches, tamper switches, plant signals or other external equipment to the fire alarm system.

Non-monitored input

A non-monitored input is an input that may only detect whether a contact is open or closed.

It may not detect wiring faults unless additional monitoring is provided.

Normally open

Normally open, or N/O, means a contact is open in its normal state and closes when operated.

Normally closed

Normally closed, or N/C, means a contact is closed in its normal state and opens when operated.

Common

Common, or COM, is the shared terminal on a changeover contact.

It switches between normally open and normally closed depending on the state of the device.

Changeover contact

A changeover contact has common, normally open and normally closed terminals.

It can switch between two states.

This is common on relays, flow switches and tamper switches.

Volt-free contact

A volt-free contact is a contact that does not provide its own voltage.

It simply opens or closes a circuit supplied by other equipment.

Also called a dry contact.

Dry contact

Dry contact means the same as volt-free contact.

It is a contact with no voltage supplied by the device itself.

Interfaces and cause and effect

Interface

An interface is a device that allows the fire alarm system to connect to another system or item of equipment.

Interfaces can receive signals, send signals, or both.

Input interface

An input interface allows another device or system to send a signal into the fire alarm system.

Examples include:

• Sprinkler flow switch
• Sprinkler valve tamper switch
• Fire suppression system signal
• Smoke control status signal
• Plant shutdown confirmation
• Door release fault signal

Output interface

An output interface allows the fire alarm system to operate or signal to another system.

Examples include:

• Releasing door holders
• Releasing access-controlled doors
• Starting smoke control
• Shutting down ventilation
• Sending a signal to a lift controller
• Sending a signal to a building management system

I/O unit

I/O unit means input/output unit.

It is a common term for an interface device.

Relay

A relay is an electrically operated switch.

Fire alarm systems use relays to send signals to other systems or switch other circuits.

Cause and effect

Cause and effect describes what the fire alarm system does when something happens.

Example:

Cause and effect should be clearly designed, tested and documented.

C&E

C&E is shorthand for cause and effect.

Engineers may write comments such as:

C&E requires testing

This means the programmed actions need to be tested.

Ancillary function

An ancillary function is an additional action carried out by the fire alarm system.

Examples include releasing doors, shutting down plant or sending signals to other equipment.

Door release

Door release means the fire alarm system releases certain doors when the alarm operates.

This may include releasing magnetic door holders or access-controlled doors, depending on the design.

Plant shutdown

Plant shutdown means the fire alarm system sends a signal to stop equipment.

Examples include air handling units, ventilation plant, gas valves or other systems that need to shut down during a fire.

Lift grounding

Lift grounding means sending lifts to a designated floor and preventing normal use during a fire condition.

The exact lift operation depends on the lift design and fire strategy.

Smoke control interface

A smoke control interface is a connection between the fire alarm system and a smoke control or AOV system.

It may start fans, open vents, close vents, or send status signals.

Sprinkler flow switch

A sprinkler flow switch detects water flow in a sprinkler system.

It can be connected to the fire alarm system to indicate sprinkler operation.

Tamper switch

A tamper switch monitors whether a valve or item of equipment has been interfered with or moved from its normal position.

On sprinkler systems, valve tamper switches are often used to show that a valve may not be correctly open.

Fire alarm conditions

Fire condition

A fire condition means the fire alarm system has received a fire alarm signal.

This may be from a detector, manual call point, interface or other initiating device.

Fault condition

A fault condition means the system has detected a problem.

Examples include:

• Device fault
• Loop fault
• Sounder fault
• Mains fault
• Battery fault
• Earth fault
• Communication fault

A fault does not always mean the whole system has failed, but it needs attention.

Disablement

A disablement means part of the system has been deliberately turned off or isolated.

Examples include:

• Detector disabled
• Zone disabled
• Sounders disabled
• Output disabled
• ARC signalling disabled

Disablements should be controlled, recorded and reviewed.

Test condition

A test condition means part of the system is placed into a test mode.

This is often used during maintenance so devices can be tested without causing full building evacuation or unwanted ARC signals, depending on the setup.

Pre-alarm

A pre-alarm is an early warning that conditions are approaching an alarm level.

It does not always mean there is a fire, but it should be investigated.

Alarm silence

Alarm silence means the alarm sounders or warning devices have been silenced after an alarm condition.

It does not usually clear the fire alarm condition.

Buzzer silence

Buzzer silence means the internal buzzer at the fire alarm panel has been silenced.

This does not silence the building fire alarm sounders unless a separate alarm silence control is used.

Reset

Reset means returning the fire alarm system to normal after the cause of the alarm has been cleared.

If the cause is still present, the system may go back into fire or fault after reset.

Evacuate button

An evacuate button is a control on the fire alarm panel or repeat panel used to manually operate the alarm sounders.

It is normally used to start evacuation manually from the panel.

Latching

Latching means the system stays in alarm or fault until it is reset, even if the original trigger clears.

Fire alarm signals are normally latching so that the event is not missed.

Non-latching

Non-latching means the condition clears automatically when the trigger clears.

This may be used for some technical signals, depending on the design.

Coincidence

Coincidence is an arrangement where an output is only given when at least two independent triggering signals are present at the same time.

It is sometimes used to reduce unwanted operation of certain outputs.

Double knock

Double knock is commonly used to mean that two signals are needed before a particular action occurs.

Strictly, it is often used for two successive signals from the same device or area, while coincidence refers to independent inputs being present at the same time.

People often use the terms loosely, so the actual cause and effect should always be checked.

Staged alarm

A staged alarm is a system where more than one stage of alarm can be given.

For example:

1. Staff alarm
2. Alert
3. Evacuate

Staged alarms are used where immediate full evacuation is not always the intended first action.

Phased evacuation

Phased evacuation means different parts of the building evacuate in a controlled sequence.

The areas at greatest risk are normally evacuated first.

This is common in some large or tall buildings.

Time-related system

A time-related system changes detector response or sensitivity depending on the time of day.

For example, a system may operate differently during occupied and unoccupied periods.

False alarms and unwanted alarms

False alarm

A false alarm is a fire alarm signal caused by something other than a real fire.

Common causes include dust, steam, cooking fumes, aerosols, insects, water ingress, accidental operation, poor detector siting or system faults.

Unwanted fire alarm signal

An unwanted fire alarm signal is normally a false alarm that has been passed to the fire and rescue service.

Reducing unwanted fire alarm signals is important because repeated false alarms can cause disruption, complacency and unnecessary emergency attendance.

Filtering

Filtering is a method used to reduce false alarms or unwanted fire alarm signals.

This may involve investigation periods, staff alarms, time delays or other arrangements, but it must be suitable for the building and fire strategy.

Investigation delay

An investigation delay is a short period that allows trained staff to investigate before a wider alarm or external signal is sent.

This is only suitable where it is properly designed, managed and agreed.

Soak period

A soak period is a period after commissioning but before handover where the system is monitored for faults and false alarms.

It helps identify problems before the system is fully accepted.

Monitoring and remote signalling

ARC

ARC stands for Alarm Receiving Centre.

It is a remote, continuously staffed centre that receives alarm signals from the premises.

The ARC may contact keyholders, notify the fire and rescue service, or follow an agreed response procedure.

Alarm transmission equipment

Alarm transmission equipment sends fire alarm signals from the premises to an ARC.

It may also send fault signals depending on the system and monitoring agreement.

Fire signal

A fire signal is a signal indicating that the fire alarm system has entered a fire condition.

Fault signal

A fault signal is a signal indicating that the system has detected a fault.

Some systems send fault signals to an ARC or remote monitoring centre.

Dual path signalling

Dual path signalling uses two different communication paths to transmit alarm signals.

For example, one path may use broadband or IP, and another may use a mobile network.

The purpose is to improve reliability if one path fails.

Single path signalling

Single path signalling uses one communication path.

It may be less resilient than dual path signalling.

Keyholder

A keyholder is a nominated person who can attend site or be contacted when an alarm or fault is reported.

URN

URN stands for Unique Reference Number.

In alarm signalling, it is commonly associated with monitored systems and emergency service response arrangements.

Power supplies and batteries

Normal supply

The normal supply is the main electrical supply that powers the fire alarm system under normal conditions.

This is usually the building’s mains electricity supply.

Mains supply

The mains supply is the 230 V electrical supply feeding the fire alarm panel or power supply unit.

The fire alarm mains supply should be dedicated to the fire alarm system and should not normally be switched off with general building supplies.

Standby supply

The standby supply is the backup power supply.

It is usually provided by rechargeable batteries and automatically powers the system if the normal mains supply fails.

Battery standby

Battery standby is the period the fire alarm system can continue operating on batteries during a mains failure.

The required standby duration depends on the system type, building use and applicable design requirements.

PSU

PSU stands for power supply unit.

It provides power to the fire alarm system or part of the system.

Some PSUs are built into panels. Others are separate units.

Charger

The charger keeps the standby batteries charged while the mains supply is healthy.

A charger fault can affect whether the batteries are ready for a mains failure.

Quiescent current

Quiescent current is the current drawn by the system when it is powered and operating normally, but not in full alarm.

In plain English:

It is the normal background current the system uses while it is sitting there monitoring the building.

This matters for battery calculations because the batteries must support the system during standby conditions.

Standing load

Standing load is another way of describing the normal background load on the power supply.

It is similar to quiescent load.

Alarm load

Alarm load is the current drawn when the system is in alarm.

This is usually higher than the quiescent current because sounders, visual alarm devices, interfaces and transmission equipment may be operating.

Maximum alarm load

Maximum alarm load is the greatest expected load on the fire alarm power supply during alarm conditions.

It includes the equipment that would operate during a fire alarm condition, such as alarm devices, outputs and transmission equipment.

Battery capacity

Battery capacity is the amount of energy a battery can store.

It is normally stated in amp-hours, written as Ah.

For example:

2 × 12 V 7 Ah batteries

Battery capacity must be suitable for the system standby and alarm requirements.

Ah

Ah means amp-hour.

It is a measure of battery capacity.

A higher Ah rating normally means the battery can support a load for longer, assuming the voltage and battery type are suitable.

Load test

A load test checks whether a battery or power supply can support a load.

During servicing, batteries may be tested to check that they remain in serviceable condition.

High resistance battery fault

A high resistance battery fault means the battery or its connections have too much resistance.

This can prevent the battery from delivering enough current during a mains failure or alarm condition.

Common causes include ageing batteries, loose terminals, corrosion or damaged leads.

Battery charger fault

A battery charger fault means the panel or PSU has detected a problem charging the standby batteries.

This should be investigated because the system may not have reliable standby power.

Mains fault

A mains fault means the normal mains supply to the fire alarm equipment has failed or been isolated.

The system may continue to operate on batteries for a period of time, but the cause should be investigated.

Documentation, testing and maintenance

Logbook

The logbook records important fire alarm events.

This may include:

• Weekly tests
• Fire alarms
• False alarms
• Faults
• Disablements
• Engineer visits
• Maintenance work
• Modifications
• Cause and effect changes

The logbook is an important part of managing the system.

Weekly test

A weekly test is a routine user test of the fire alarm system.

It is normally carried out by operating a manual call point and confirming that the alarm signal operates.

The result should be recorded in the logbook.

Routine testing

Routine testing is regular testing carried out by the user or premises management.

It is not the same as full servicing by a competent fire alarm engineer.

Servicing

Servicing is routine work carried out at planned intervals to check and maintain the system.

It may include inspection, testing, cleaning, adjustment and replacement.

Maintenance

Maintenance includes inspection, servicing and repair needed to keep the system operating efficiently.

Repair

A repair is non-routine work needed to restore the system to proper operation.

For example, replacing a faulty detector, repairing a damaged cable or resolving a loop fault.

Commissioning

Commissioning is the process of checking that an installed system meets the defined requirements.

It happens before handover and acceptance.

Handover

Handover is the stage where the completed system, documentation and responsibilities are passed to the user or premises management.

Acceptance

Acceptance is the client or user accepting the completed system.

The date of acceptance can be important for maintenance records and future reference.

Verification

Verification is a check that the system design, installation or work meets the relevant requirements.

It may be carried out where independent confirmation is needed.

Design certificate

A design certificate confirms the design responsibility and the category, standards and any variations relating to the system design.

Installation certificate

An installation certificate confirms the installation work carried out and whether it conforms to the relevant requirements and design information.

Commissioning certificate

A commissioning certificate confirms that the system has been commissioned and tested against the defined requirements.

Inspection and servicing certificate

An inspection and servicing certificate records the outcome of a periodic service visit.

It should identify defects, limitations, recommendations and work carried out.

Variation

A variation is an agreed departure from the recommendations of the standard.

Variations should be agreed by relevant interested parties, justified and recorded.

A variation is not the same as simply doing something incorrectly.

Non-conformity

A non-conformity is something that does not conform to the relevant standard, design or requirement.

It may need correction, justification, risk assessment or agreement depending on the situation.

Defect

A defect is a problem with the system or installation.

Examples include faulty equipment, damaged cable, missing labels, incorrect programming or failed batteries.

Limitation

A limitation is something that restricts the inspection, test, design or maintenance work.

For example, an engineer may not be able to access certain rooms or test certain interfaces during a visit.

People and responsibilities

User

The user is the person or organization having control of the building or part of the building where the fire alarm system is installed.

This does not necessarily mean a person using the system day to day; it can mean the organization responsible for the premises.

Premises management

Premises management means the person or people with day-to-day control of the premises, the fire alarm system and fire procedures.

In a small building this may be one person. In a large building it may be a facilities team, building manager or specialist fire safety manager.

Responsible person

The responsible person is a term used under fire safety legislation.

This is normally the employer, building owner, occupier or person in control of the premises, depending on the situation.

The responsible person has legal duties relating to fire safety.

Competent person

A competent person is someone with suitable training, knowledge, experience and instructions to carry out the required task correctly.

Different tasks require different levels of competence.

For example, weekly user testing and full fire alarm design are not the same level of task.

Designer

The designer is the person or organization responsible for the fire alarm system design.

Installer

The installer is the person or organization responsible for installing the system or part of the system.

Commissioning engineer

A commissioning engineer is the person who checks, tests and sets up the installed system before handover.

Maintenance organization

The maintenance organization is the company or organization responsible for routine inspection, servicing and repair.

Interested parties

Interested parties are people or organizations who may need to be consulted or agree certain decisions.

Examples include:

• User
• Purchaser
• Designer
• Installer
• Fire risk assessor
• Building control body
• Fire and rescue authority
• Property insurer
• Fire engineer
• Facilities management team

Common engineer shorthand

Device

A device is a general term for something connected to the fire alarm system.

Examples include detectors, call points, sounders, interfaces and isolators.

Head

Head usually means detector head.

Example:

Replace faulty head in Room 12

This normally means replacing the detector head, not the whole base or wiring.

Base

Base usually means detector base.

The detector head plugs into the base.

Module

A module is another word for an interface or electronic unit connected to the system.

Examples include input modules, output modules and relay modules.

Address

An address is the unique number or identity given to a device on an addressable system.

It allows the panel to identify that specific device.

Text label

A text label is the description shown on the fire alarm panel for a device or zone.

Example:

Smoke Detector - Office 2.03

Good text labels make alarm investigation much easier.

Device missing

Device missing means the panel can no longer communicate with a device it expects to see.

Possible causes include a removed detector, damaged device, wiring fault, addressing issue or programming issue.

Device dirty

Device dirty means a detector may be contaminated with dust or dirt.

Some systems can detect this and report a maintenance warning.

Contamination

Contamination means dirt, dust, insects, moisture or other material affecting a detector or device.

Contamination can cause false alarms or faults.

Chamber

The chamber is the sensing area inside some smoke detectors.

If the chamber becomes dirty or contaminated, the detector may become unreliable.

Drift

Drift means the detector’s normal reading has gradually changed over time.

This can happen due to contamination, ageing or environmental conditions.

Calibration

Calibration is the process of setting or checking equipment against known values.

Most modern fire alarm detectors are not calibrated on site in the way some instruments are, but the term may still be used informally.

Sensitivity

Sensitivity describes how readily a detector responds to signs of fire.

Higher sensitivity may detect fire earlier but may also increase false alarm risk if used in the wrong environment.

Day/night mode

Day/night mode means the system may operate differently at different times.

For example, detector sensitivity or staff investigation delays may change between occupied and unoccupied periods.

Walk test

Walk test is a test mode used by engineers to test devices.

The system may automatically reset devices after activation during testing, depending on the panel and setup.

One-out, all-out

One-out, all-out is informal language meaning that one fire activation causes the alarm to sound throughout the building.

This is common in smaller simultaneous evacuation buildings.

Simultaneous evacuation

Simultaneous evacuation means everyone in the relevant building or area evacuates at the same time when the fire alarm operates.

Stay put

Stay put is a fire strategy commonly associated with purpose-built blocks of flats.

It does not mean “ignore every alarm”. It means occupants not directly affected by fire may be expected to remain in their flats unless affected, instructed otherwise, or the strategy changes.

Communal fire alarm systems in flats require careful consideration and should not be assumed to be required or appropriate without proper fire strategy and risk assessment input.

Cause

In cause and effect programming, the cause is the input or event.

Example:

Smoke detector in riser operates

Effect

In cause and effect programming, the effect is what the system does in response.

Example:

Start smoke extract fan and open vent

Output delay

An output delay is a programmed delay before an output operates.

This must be carefully considered because delayed outputs can affect life safety systems.

Investigation period

An investigation period is time allowed for trained staff to investigate an alarm before further action occurs.

It must be suitable for the building and properly managed.

Dependency

A dependency is where one system relies on another system or signal to operate correctly.

For example, a smoke control system may depend on the fire alarm system to provide a trigger signal.

Interface cause and effect matrix

An interface cause and effect matrix is a table showing what inputs operate what outputs.

It is especially useful on complex sites where fire alarms connect to lifts, smoke control, access control, sprinklers or plant.

Useful fault wording

Loop fault

A loop fault means there is a problem on an addressable loop.

It may be an open circuit, short circuit, earth fault, device fault or communication issue.

Zone fault

A zone fault usually means a problem on a conventional zone circuit.

It may be caused by wiring, a detector, a call point, an end-of-line device or a damaged connection.

Sounder fault

A sounder fault means there is a problem with the alarm warning devices or their circuit.

This can be important because people may not hear the alarm in affected areas.

Comms fault

A comms fault means communication has failed between parts of the system.

Examples include panel-to-panel network faults, loop communication faults or signalling equipment faults.

PSU fault

A PSU fault means a power supply unit has reported a problem.

This may involve mains, batteries, charger, output voltage or internal electronics.

Charger fault

A charger fault means the system may not be correctly charging the standby batteries.

Battery fault

A battery fault means the standby batteries or battery circuit have a problem.

This should not be ignored, because the system may not operate correctly during a mains failure.

Earth leakage

Earth leakage is often used informally to describe current leaking to earth or an insulation issue.

On fire alarm systems, it may appear as an earth fault.

Open circuit

Open circuit means the circuit path is broken.

Short circuit

Short circuit means conductors are connected together where they should not be.

Head removed

Head removed means a detector head has been removed from its base.

On many systems this creates a fault.

Double address

Double address means two addressable devices have been set or learnt with the same address.

This can cause communication problems and incorrect device reporting.

Wrong device type

Wrong device type means the panel expected one type of device but found another.

For example, the panel expected a smoke detector but found a heat detector.

Device not recognised

Device not recognised means the panel can see something on the system but does not recognise it correctly.

This may be due to compatibility, programming, addressing or device failure.

Outstation

An outstation is a remote unit connected to the system.

The term is more common on some life safety systems than others, but may be used for remote panels, interfaces or field equipment.

Common abbreviations

Summary

Fire alarm terminology can be confusing because it mixes formal standard definitions, manufacturer language, engineer shorthand and site-specific wording.

The key points are:

• A fire condition is not the same as a fault condition.
• A fault does not always mean the whole system has failed.
• A disablement is deliberate and should be controlled.
• A zone may mean a detection zone or an alarm zone.
• A sounder fault can be more urgent than it first sounds.
• Quiescent current is the normal background current used for battery calculations.
• Cause and effect tells the system what to do when something happens.
• Interfaces matter because the fire alarm may control other life safety systems.

When in doubt, record the exact wording shown on the panel or report and ask a competent fire alarm engineer to confirm what it means.