Why does my fire alarm keep going off for no reason?

Repeated false alarms (false activations without a fire condition) from a fire detection system are most commonly caused by: detector contamination (dust, insects, or cooking fumes in or near the detector), inappropriate detector type for the environment (ionisation detectors near kitchens, optical detectors in dusty areas), low standby battery causing voltage-related false activations, or wiring faults causing intermittent signal noise on the zone loop. The BS 5839-1 false alarm management protocol requires investigation and rectification after more than 10 false alarms per zone per year.

What is a fire alarm zone fault?

A zone fault is reported by the fire alarm panel when the resistance or continuity of a zone circuit is outside the acceptable range. An open-circuit zone fault (resistance too high or infinite) can be caused by a broken wire, a failed detector, or a loose terminal connection. A short-circuit zone fault (resistance too low) can be caused by insulation damage between conductors, a failed device, or water ingress into a detector or junction box. The affected zone loses its detection capability until the fault is rectified.

How often must a fire alarm be serviced?

BS 5839-1:2025 clause 43.2.1 recommends inspection and servicing by a competent person at intervals of approximately 6 months; anywhere from 5 to 7 months after the last visit is acceptable. Between visits the user tests the system every week by operating a manual call point, a different one each week, and records it in the logbook (clauses 42.1.2 to 42.1.6). Homes are covered by BS 5839-6 instead. More frequent servicing is required in high-risk environments.

Can a general electrician service a fire alarm?

A general electrician can carry out electrical work on the mains supply to the fire alarm panel (the dedicated circuit from the consumer unit) and can replace a detector of the same type and specifications without reprogramming on a conventional system. However, fault finding on the fire alarm panel itself, reprogramming an addressable system, or commissioning or modifying a fire alarm installation requires a competent fire alarm engineer — someone trained and experienced specifically in fire alarm systems, which is a separate competency from general electrical installation work.

What is the difference between a conventional and addressable fire alarm?

A conventional fire alarm divides the building into zones, each with a wired loop of detectors and call points. When a device activates, the panel identifies the zone but not the specific device. An addressable (intelligent) fire alarm gives each device a unique address; when a device activates or reports a fault, the panel identifies the precise device. Addressable systems are the usual choice in larger or more complex premises and make fault finding significantly easier — the panel identifies the specific device rather than just the zone.

What should I do if the fire alarm panel shows a fault but no alarm?

A fault condition (typically shown by an amber LED and a fault description on the panel display) indicates a problem with the fire alarm system that does not represent an active fire signal. The building does not need to be evacuated. Record the fault description, investigate the cause using the guidance in this page, and arrange for a competent fire alarm engineer to rectify the fault as soon as practicable. The fault log in the fire alarm log book must be updated. Do not simply silence and ignore repeated fault conditions.

My fire alarm is chirping or beeping — what does this mean?

A repeated chirping or beeping sound from a fire alarm panel or sounder, without a full alarm activation, almost always indicates a power supply fault — most commonly a low or failing standby battery. Some panels emit a slow beep for a mains power loss and a faster beep for a low battery. Check the panel display for a fault message, check that the mains supply to the panel is intact, and arrange battery replacement if indicated. Do not silence a chirping alarm and leave it uninvestigated.

FAULT FINDING GUIDE

Fire Alarm Fault Finding: Fire Detection System Problems Explained

Your fire alarm is showing a fault condition, producing false alarms, or failing to function correctly. This guide covers zone faults, detector contamination, panel faults, power supply issues, BS 5839 compliance, and when you must use a competent fire alarm engineer.

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13 min readUpdated 2026-10-24Andrew Moore, Founder of Elec-Mate

Written and reviewed by Andrew Moore, founder of Elec-Mate, against BS 7671:2018+A4:2026, IET Guidance Note 3 and the IET On-Site Guide.

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The short answer

What does a fault light on a fire alarm panel mean?

A fault (amber) indication means the panel has found a problem that could stop the system working, not a fire. The usual causes are an open or short circuit on a zone or loop, a failed or removed detector, a flat or disconnected standby battery, or loss of mains. Read the panel message, record it in the logbook and get a competent fire alarm engineer to repair it.

BS 5839-1:2025 asks for servicing about every 6 months (cl. 43.2.1) and a weekly call point test (cl. 42.1).

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Key takeaways

01Non-domestic fire alarm systems follow BS 5839-1:2025, which replaced the 2017 edition on 30 April 2025. Clause 43.2.1 recommends inspection and servicing by a competent person at intervals of approximately 6 months (any time between 5 and 7 months is acceptable).
02Zone faults — where the panel reports that a zone has an open or short circuit — are among the most common fire alarm faults. They are caused by wiring faults, device failures, or incorrect device connections within the zone loop.
03Detector contamination is the most common cause of false alarms from optical smoke detectors. Dust, insects, and steam ingress cause the detector's optical chamber to scatter light and trigger a fire signal. Contaminated detectors must be cleaned or replaced.
04Fire alarm panel faults — including CPU errors, memory corruption, and power supply module failure — require investigation by a competent fire alarm engineer, not a general electrician. Working inside a fire alarm panel without appropriate training risks disabling the fire detection system.
05BS 5839-1 recommends that the panel is checked for faults at least once every 24 hours where practicable (clause 47.1), and that a fault indication is never concealed when a defect cannot be fixed on the visit (clause 44.2.4).
06Critical signal paths and the mains supply to the panel need standard or enhanced fire-resisting cable (BS 5839-1 clause 25.2; BS 7671 Regulation 560.8.1). Clause 25.9 adds that all fire alarm cables and the mains supply should be one common colour not used for other services, preferably red.
07Safety circuits must be independent of other circuits (BS 7671 Regulation 560.7.1). BS 5839-1 clause 35.9 keeps mains-voltage fire alarm cables segregated from ELV fire alarm circuits, and clause 35.8 defers to the panel maker on separation from other services.
08The panel supply should not be RCD protected unless BS 7671 makes it necessary. Where it is, a fault on any other circuit must not be able to cut the fire alarm supply (BS 5839-1 clause 24.1.10).

01 · Fault Finding Guide

Zone Faults

A zone fault is one of the most common conditions displayed on a fire alarm panel. It indicates that the resistance of the zone detection loop is outside the panel's acceptable range — either too high (open circuit) or too low (short circuit). A zone in fault condition cannot detect a fire condition in that area until the fault is rectified, making prompt investigation essential.

Open-circuit zone fault — caused by a broken conductor in the zone wiring, a loose or corroded terminal connection, or a failed detector or call point. On a conventional system, isolate sections of the zone loop to locate the break. On an addressable system, the panel identifies the specific device or loop segment where the open circuit exists.
Short-circuit zone fault — caused by insulation damage between the two conductors of the zone loop (often due to mechanical damage, rodent attack, or water ingress), an incorrectly wired device, or a device with an internal short circuit. Short-circuit faults on conventional systems render the entire zone inoperative. Addressable systems with short-circuit isolators (SCI) can isolate the fault and maintain operation of the remaining devices on the loop.
Device failure — a detector or call point with an internal fault can cause a zone fault. On addressable systems, the panel identifies the specific device address. Replace the device with the correct specified type and re-commission if required.
Interim measures — while a zone fault is active, the fire risk assessment for the premises must be reviewed. Where an entire zone is out of service, additional fire watch patrols or temporary detection measures may be required. Notify the responsible person and record the fault condition in the fire alarm log book.

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02 · Fault Finding Guide

Detector Contamination

Detector contamination is the leading cause of false alarms in optical smoke detection systems and one of the most common reasons for detector failure. Where false alarms cannot be explained, BS 5839-1 clause 44.3.2 says each recognised cause in clause 30 should be confirmed or ruled out in turn, and every false alarm is logged with its cause (clause 48.1).

Dust contamination — the most common contaminant in optical smoke detectors. Dust particles settle in or near the optical chamber and scatter light, creating a signal that the detector interprets as smoke. Detectors in dusty environments (construction sites, food production, woodworking) require more frequent inspection and cleaning or should be replaced with a detector type more suitable for the environment.
Insect intrusion — insects entering the optical chamber of a smoke detector are a well-documented cause of false alarms. Inspect detectors in areas with insect activity and consider insect-resistant detector designs for vulnerable installations.
Steam and cooking fumes — detectors located too close to kitchens, shower rooms, or steam sources are exposed to high humidity and aerosol particles that can trigger false alarms. Re-siting the detector, or changing the detector type where the system design allows, is the lasting fix; cleaning it again only buys time.
Cleaning procedure — approved cleaning of a smoke detector involves careful vacuuming of the detector chamber using a soft brush attachment. Never use compressed air (which forces contamination deeper into the chamber), cleaning solvents, or water. If the detector continues to false alarm after cleaning, replace it.

03 · Fault Finding Guide

Fire Alarm Panel Faults

The fire alarm control panel (FACP) is the system hub — it monitors all zone loops and devices, processes fire and fault signals, and controls output functions including sounders, evacuation interfaces, and remote signalling. Panel faults require immediate attention from a competent fire alarm engineer.

System fault / CPU fault — a fault reported against the panel itself (rather than a zone or device) indicates an internal panel hardware or software fault. This may be a failed output module, a firmware corruption, or a hardware component failure. Do not attempt to open the panel or probe the electronics — contact the fire alarm installer or manufacturer.
Memory or programming fault — addressable fire alarm panels store device programming in non-volatile memory. Memory corruption (typically caused by a voltage transient or battery failure during programming) can cause the panel to report all devices as faulted or to behave erratically. A programming reload from a backup may be required.
Sounder or relay module fault — a fault on the sounder supply circuit or relay output module will prevent the sounders or ancillary outputs from operating during a fire signal. This is a critical life-safety fault — the building evacuation signalling capability is compromised. Arrange urgent repair.

Isolating a faulty zone or device on a fire alarm panel using the panel's own isolation function is within the capability of a trained user. Opening the panel enclosure to work on the electronics is not — this must be done by a competent fire alarm engineer.

04 · Fault Finding Guide

Power Supply Issues

Fire alarm control panels require a reliable mains power supply and a standby battery capable of maintaining system operation for a minimum period following mains failure. BS 5839-1 clause 24.3.5 sets the minimum standby capacity.

Mains power loss — the panel should indicate mains power loss via an amber LED and continue operating from the standby battery. The mains supply circuit must be restored as soon as possible. BS 5839-1 clause 24.1.2 has it taken through an isolating protective device such as a circuit-breaker, from the dead side of the building's main isolator. A mains supply that is frequently interrupting — without a known power cut — indicates a wiring fault or MCB problem on the dedicated circuit.
Standby battery fault — a battery fault reported by the panel indicates that the standby battery has failed, is not connected, or is not accepting charge. Replace with the battery type and capacity specified in the panel documentation. For Category M and L systems, clause 24.3.5 asks for at least 24 hours of standby followed by 30 minutes of evacuate signal in all zones, unless an automatically started standby generator is fitted.
PSU module failure — the power supply unit within the fire alarm panel converts mains AC to the panel's DC operating voltage and charges the standby battery. A failed PSU module causes both mains power fault and battery fault indicators. PSU replacement must be carried out by a competent fire alarm engineer using the correct spare part for the panel model.

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05 · Fault Finding Guide

BS 5839 Compliance and Legal Requirements

BS 5839-1:2025 is the UK code of practice for fire detection and alarm systems in non-domestic buildings. While it is not itself a statutory document, it is referenced in guidance to the Regulatory Reform (Fire Safety) Order 2005, which imposes legal duties on responsible persons in non-domestic premises. Non-compliance with BS 5839-1 can result in enforcement action by the fire authority.

Six-monthly servicing — clause 43.2.1 recommends inspection and servicing by a competent person at intervals of approximately 6 months (5 to 7 months is acceptable). At each visit, all detectors, call points, sounders, and panel functions must be tested. The service certificate and log book must be updated.
Weekly user test — every week, at about the same time, the user operates a manual call point to prove the panel processes a fire signal and drives the sounders. A different call point is used each time and the result is logged (clauses 42.1.2 to 42.1.6). Sounders should run for at least 5 s but not normally more than 60 s (clause 42.1.7).
Fire alarm log book — the log book must record every test, every fault event and its resolution, every false alarm, and all maintenance work carried out on the system. The log book should be kept adjacent to the fire alarm panel and be readily accessible to the fire authority on request.
BAFE certification — the British Approvals for Fire Equipment (BAFE) scheme provides third-party certification for fire alarm maintenance companies. Many insurance policies and local authority licence conditions require that fire alarm maintenance is carried out by a BAFE-registered company.

06 · Fault Finding Guide

When to Use a Competent Person

The term "competent person" in the context of fire alarm systems has a specific meaning under BS 5839-1. It refers to a person who has sufficient training, experience, and knowledge of fire alarm systems to safely carry out the work in question — which is a higher bar than a general electrical qualification.

Work requiring a fire alarm competent person — fault finding on zone loops and devices, detector replacement on addressable systems requiring programming, panel configuration or reprogramming, commissioning, any modification to the system design, and all formal servicing visits. This is the majority of fire alarm work.
Work a general electrician can carry out — the dedicated mains supply circuit to the fire alarm panel, including the MCB, cable, and termination at the panel. This is standard electrical installation work. The electrician should not need to access the panel's internal electronics.
Do not disable or silence persistent faults — a fire alarm fault that cannot be resolved must be reported to the responsible person and a competent fire alarm engineer called promptly. In the interim, the fault condition should be left on the panel display (not permanently silenced) and recorded in the log book. Silencing a persistent fault without investigation creates a false sense of security.

07 · Fault Finding Guide

For Electricians: Fire Alarm Electrical Work and Certification

Electricians working in commercial premises will regularly encounter fire alarm systems as part of EICR work, new installation projects, and maintenance contracts. Understanding the boundary between electrical installation work and fire alarm engineering is essential for both safety and liability reasons.

Fire Alarm on the EICR

When carrying out an EICR on commercial premises, inspect and test the dedicated mains supply circuit to the fire alarm panel. Record the circuit details, test results, and note the fire alarm system type in the schedule of particulars. Use the Elec-Mate EICR app to capture all observations and generate the report on site.

Fire Alarm Installation Certificates

If you are a competent fire alarm engineer, use the Elec-Mate fire alarm certificate app to generate installation and commissioning certificates on site. Covers system type, zone schedule, device schedule, test results, and BS 5839-1 compliance fields.

Wiring Requirements: Fire-Resistant Cable

BS 7671 Regulation 560.8.1 requires safety services that must work in a fire to use mineral-insulated cable, cable tested to IEC 60331, BS EN 50200, BS 8434 or BS 8491, or a wiring system that keeps the necessary fire and mechanical protection. BS 5839-1 clause 25.2 applies this to every critical signal path and to the mains supply to the panel, in two grades: standard (clause 25.5, 30 minutes, class PH 30, the grade FP200 Gold and similar cables meet) and enhanced (clause 25.6, 120 minutes, class PH 120). Clause 25.4 calls for enhanced cable in, for example, unsprinklered buildings over 30 m tall or with phased evacuation in four or more phases. General-purpose PVC twin and earth meets neither grade; where it is found on detector or sounder wiring during an EICR, record it and refer the system to a fire alarm engineer.

EICR: Segregation and RCD Omission

Segregation and colour: circuits of safety services must be independent of other circuits (BS 7671 Regulation 560.7.1), and safety circuit cables that are not metal-screened fire-resistant types must be separated from other circuits by distance or barriers (Regulation 560.7.7). BS 5839-1 clause 25.9 asks for all fire alarm cables and the panel's mains supply to be one common colour not used for general services, preferably red.

RCDs on the panel supply: BS 5839-1 clause 24.1.10 says the circuit supplying the fire alarm should not be RCD protected unless that is necessary to meet BS 7671. Where it is necessary, a fault on any other circuit must not be able to cut the fire alarm supply, which in practice means its own RCBO rather than a shared RCD.

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