Why is my emergency light flashing or showing a red fault indicator?

A red LED indicator on an emergency lighting fitting typically signals one of three conditions: low or failed battery (the most common cause), a failed lamp (the fitting cannot illuminate on test), or a charging circuit fault (the battery is not receiving charge from the maintained circuit). Some fittings indicate a fault by flashing the green charge indicator rather than illuminating a separate red LED. Refer to the fitting manufacturer's indicator guide — the pattern is usually in the installation instructions on the fitting itself.

How long must emergency lighting last in a power cut?

Under BS 5266-1:2016, emergency lighting must provide at least 3 hours of illumination at the specified lux level following complete mains failure for most commercial premises. Premises with a low occupancy risk category may qualify for a 1-hour duration. The 3-hour figure is the most common requirement. During the annual test, the fitting must sustain illumination for the full rated duration without the battery voltage dropping below the minimum specified threshold.

Can I test emergency lighting myself?

The monthly function test can be carried out by a responsible person with appropriate training — it involves pressing the test button on each fitting (or operating the maintained circuit isolator) and observing that the fitting illuminates during the test period (typically 25% of rated duration, i.e. 45 minutes for a 3-hour fitting). The annual full-duration test requires the battery to be fully charged first (24 hours minimum after any previous test) and the results must be recorded in the log book. Test results must be documented.

How often should emergency lighting batteries be replaced?

Emergency lighting batteries should be replaced every 3 to 4 years for sealed lead-acid (SLA/VRLA) batteries, or every 4 to 5 years for NiCd batteries, under normal operating conditions. In practice, the annual duration test will reveal batteries approaching end of life — a fitting that illuminates during the function test but fails before the end of the duration test period needs a battery replacement. Always replace with the exact battery specification from the fitting's documentation.

What is the difference between maintained and non-maintained emergency lighting?

Maintained emergency lighting is illuminated at all times (both when the mains supply is normal and during a mains failure). It is required in areas of public assembly, entertainment venues, and any location where occupants need continuous guidance. Non-maintained emergency lighting is only illuminated during a mains failure. The choice between maintained and non-maintained is determined during the system design process based on the premises use and risk assessment. BS 5266-1 provides guidance on selection.

What records must be kept for emergency lighting?

BS 5266-1:2016 requires that a log book is maintained for every emergency lighting system. The log book must record: the date and result of every monthly function test, the date and result of every annual duration test, all defects found and remedial action taken, the date of any battery or lamp replacements, and details of any alterations to the system. The log book should be kept on the premises and made available to the fire authority or building authority on request.

My emergency lighting passes the monthly test but fails the annual test — why?

A fitting that illuminates on the monthly function test (which only requires 25% of rated duration) but fails the annual full-duration test most commonly has a battery that has partially degraded. The battery holds enough charge for a short test but cannot sustain the full 3-hour output. Less commonly, a charging circuit fault is allowing the battery to partially charge but not reach full capacity. Replace the battery first; if the annual test fails again, investigate the charging circuit.

FAULT FINDING GUIDE

Emergency Lighting Not Working: Fault Finding and BS 5266 Compliance

Your emergency lighting is failing tests, showing fault indicators, or failing to illuminate during a mains failure. This guide covers battery failure, charging circuit faults, lamp failure, test mode issues, and the monthly and annual BS 5266 testing requirements.

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12 min readUpdated 2026-05-18Andrew 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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Key Takeaways

1Emergency lighting must comply with BS 5266-1:2016 (Code of practice for the emergency lighting of premises). Failure to maintain emergency lighting in commercial, public, and HMO premises is a breach of fire safety legislation and can result in enforcement action.
2The most common emergency lighting fault is battery failure — sealed lead-acid or NiCd batteries degrade over time and may not sustain the minimum 3-hour duration (or 1-hour for some categories) required by BS 5266-1. Battery replacement is the most frequent maintenance intervention.
3Charging circuit faults prevent the battery from reaching full charge. A fitting that passes the monthly function test but fails the annual duration test often has a charging circuit fault rather than a completely failed battery.
4Emergency lighting fittings must be tested monthly (a function test of at least 25% rated duration) and annually (a full rated-duration discharge test). Both test results must be recorded in a log book as required by BS 5266-1.
5Central battery systems and addressable emergency lighting systems require specialist knowledge to fault find. Individual self-contained fitting failures are within the capability of a competent electrician, but system-level faults on central battery installations should be referred to the system installer.

01 · Fault Finding Guide

Battery Failure

Battery failure is the most common cause of emergency lighting faults. Every self-contained emergency lighting fitting contains a rechargeable battery — most commonly a sealed lead-acid (VRLA) or NiCd cell — that powers the lamp during a mains failure. These batteries degrade through charge cycles and calendar ageing, eventually failing to hold sufficient charge for the required duration.

Symptoms of battery failure — the fitting illuminates briefly during a test but extinguishes before the test period expires, a red fault indicator is lit on a fitting that otherwise appears to be operating, or the fitting fails to illuminate at all during a simulated mains failure.
Battery lifespan — sealed lead-acid batteries in emergency lighting fittings typically last 3 to 4 years. NiCd batteries (increasingly rare in new fittings due to EU RoHS restrictions) may last slightly longer. Replace batteries proactively at the manufacturer's recommended interval, not just when they fail.
Correct replacement specification — always replace with the battery type and capacity specified in the fitting's documentation. An incorrect capacity (Ah rating) will result in a fitting that either does not reach full charge or provides insufficient duration. An incorrect voltage will damage the charging circuit.
Charge recovery period — after fitting a new battery, the fitting must be left on mains supply for a full recharge period (typically 24 hours for lead-acid, up to 24 hours for NiCd) before a duration test is performed. Testing too soon after battery replacement will give a falsely short duration result.

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02 · Fault Finding Guide

Charging Circuit Faults

The charging circuit within each self-contained fitting converts the maintained mains supply to the correct DC charge voltage for the battery. A fault in the charging circuit means the battery is not being recharged after each test or after a real mains failure event — the battery progressively discharges until the fitting fails completely.

Identifying a charging fault — measure the DC voltage across the battery terminals with the mains supply connected. The voltage should be above the battery's nominal voltage (typically 3.6 V to 4.2 V for a NiCd cell, or 2.15 V per cell for a lead-acid battery in float charge). A battery voltage below nominal with the mains supply on indicates a charging circuit fault.
Failed charging components — the charging circuit typically consists of a voltage regulator IC, current-limiting resistors, and a diode. Failure of any of these components will prevent charging. Component-level repair of emergency lighting PCBs is generally not cost-effective — replace the fitting.
Mains supply interruption — if the maintained mains circuit to the emergency lighting has been interrupted (tripped MCB, blown fuse, or isolation left on following maintenance), the fittings receive no mains supply and the batteries progressively discharge. Check that the emergency lighting circuit MCB is closed and that no local isolation has been left in the off position.

03 · Fault Finding Guide

Lamp Failure

Modern emergency lighting fittings use LED light sources with very long service lives — typically 50,000 hours or more — making lamp failure much less common than with older fluorescent or incandescent sources. However, LED modules can still fail, particularly in fittings exposed to heat, vibration, or repeated voltage transients.

LED module failure — a fitting that does not illuminate during a test but has a satisfactory battery voltage is most likely suffering from LED module failure or a driver PCB fault. LED modules in emergency lighting fittings are not typically user-replaceable — replace the fitting.
Maintained lamp vs. emergency lamp — some combined maintained and emergency fittings have separate lamp circuits for the mains-powered maintained operation and the battery-powered emergency operation. A fault in the maintained lamp circuit does not affect the emergency lamp, and vice versa. Confirm which lamp has failed before replacing the fitting.
Luminance and lux levels — BS 5266-1 specifies minimum illuminance levels (typically 1 lux on the centreline of escape routes, higher in high-risk areas). A fitting with degraded LEDs may illuminate but fail to meet the minimum lux requirement. Annual testing should include lux verification at representative points on the escape route.

04 · Fault Finding Guide

Test Mode Issues

Addressable and central battery emergency lighting systems allow testing via a central controller rather than by testing each fitting individually. Faults in the test mode system can prevent testing from being completed or can provide false test results.

Test inhibit left active — some systems allow a test inhibit to be set (for example, to prevent an automatic test running during an event). An inhibit that has been left active will prevent the scheduled test from running. Check the controller settings and remove any active inhibits.
Communication fault preventing remote test — on bus-connected addressable systems, a wiring fault on the bus loop will prevent communication with all downstream fittings. The controller will report a communication fault rather than a test result. The loop wiring must be repaired before testing can proceed.
Manual test as alternative — if the automated test system is faulty, the monthly and annual tests can still be performed manually by simulating mains failure at each fitting. Manual test results must still be recorded in the log book. Restore the automatic test function as soon as practicable.

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05 · Fault Finding Guide

Monthly Self-Test Requirements

BS 5266-1:2016 requires that emergency lighting is subject to a monthly function test. This is a key maintenance obligation for commercial premises, HMOs, and any building where emergency lighting is installed as a fire safety measure.

Test procedure — simulate mains failure by pressing the test button on each self-contained fitting, or by operating the maintained circuit isolator for central battery systems. Each fitting must be visually confirmed to illuminate. The test period should be at least 25% of the rated duration (45 minutes for a 3-hour rated fitting).
Allow recharge before next test — after the monthly function test, the battery must be allowed to fully recharge (minimum 24 hours) before the next test or before the premises are closed. Do not carry out multiple tests in quick succession.
Recording results — the date of the test, the tester's name, and the result (pass or fail, with the identity of any failed fitting) must be recorded in the emergency lighting log book. Unsigned or undated log book entries are not acceptable evidence of compliance.

06 · Fault Finding Guide

Annual BS 5266 Duration Test

The annual full-rated-duration test is the most rigorous maintenance requirement for emergency lighting. It confirms that each fitting can sustain illumination for the complete rated duration — typically 3 hours — following complete mains failure, meeting BS 5266-1:2016.

Pre-test battery charge — all fittings must be fully charged before the annual test begins. This requires at least 24 hours on mains supply following any previous test or mains failure event. Beginning the annual test with partially charged batteries will give misleadingly low duration results.
Test execution — simulate complete mains failure across the installation and monitor all fittings throughout the full rated duration. Any fitting that extinguishes before the end of the duration period has failed the test and must be repaired or replaced and retested.
Post-test recharge and restrictions — after the annual test, the batteries are fully discharged. The premises should not be occupied during the recharge period (typically 24 hours) unless alternative emergency lighting arrangements are in place. This is a significant operational consideration for busy commercial premises.
Formal certificate — the annual test should be documented with a formal test certificate signed by the competent person who carried out the test. This certificate forms part of the fire safety record for the premises and may be required by the fire authority or building insurer.

07 · Fault Finding Guide

For Electricians: Emergency Lighting Testing and Certification

Emergency lighting testing and maintenance is a steady source of recurring work for commercial electricians. Every commercial and public building, HMO, and licensed premises requires monthly testing and an annual duration test — creating a regular maintenance cycle for every customer on your books.

Emergency Lighting on the EICR

When carrying out an EICR on premises with emergency lighting, function-test each fitting and record any failures as C2 or C3 observations. Record the results and the date of the last annual test in the schedule of particulars. Use the Elec-Mate EICR app to capture observations and generate the report on site.

Annual Test Certificates

The annual BS 5266 duration test requires a formal written certificate. Elec-Mate allows you to capture test results for each fitting, record pass and fail status, and generate a professional test certificate — all on your phone, on site. Upsell annual testing contracts to every commercial EICR customer.

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Frequently Asked Questions About Emergency Lighting Faults

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Emergency Lighting Not Working: Fault Finding and BS 5266 Compliance

Key Takeaways

Battery Failure

Get the BS 7671 A4:2026 Cheat Sheet — free

Charging Circuit Faults

Lamp Failure

Test Mode Issues

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Monthly Self-Test Requirements

Annual BS 5266 Duration Test

For Electricians: Emergency Lighting Testing and Certification

Emergency Lighting on the EICR

Annual Test Certificates

Manage emergency lighting testing with Elec-Mate

Frequently Asked Questions About Emergency Lighting Faults

Why is my emergency light flashing or showing a red fault indicator?

How long must emergency lighting last in a power cut?

Can I test emergency lighting myself?

How often should emergency lighting batteries be replaced?

What is the difference between maintained and non-maintained emergency lighting?

What records must be kept for emergency lighting?

My emergency lighting passes the monthly test but fails the annual test — why?

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