Why Emergency Lighting Systems Fail: Common Causes and How to Prevent Them
Emergency lighting exists for one reason — to guide people to safety when the normal lights go out. When it fails, the consequences can be catastrophic. Yet across Manchester and the wider UK, emergency lighting system failures are discovered with alarming regularity during annual duration tests and fire risk assessments. In many cases, building owners had no idea there was a problem until the system was put to the test.
Understanding why emergency lighting fails is the first step toward preventing it. This guide covers the most common causes of failure, the warning signs to watch for, and the practical steps you can take to ensure your system works when it matters most.
The Scale of the Problem
Emergency lighting failures are far more common than most building owners realise. Industry data suggests that between 20 and 30 per cent of emergency luminaires fail their annual three-hour duration test in buildings where maintenance has been neglected. Even in well-maintained buildings, individual unit failures occur, which is precisely why regular testing is a legal requirement under the Regulatory Reform (Fire Safety) Order 2005.
The problem is particularly acute in older commercial buildings across Manchester, where emergency lighting may have been installed decades ago and has received only sporadic attention since. In these environments, the failure rate can be significantly higher.
Common Cause 1: Battery Degradation
Battery failure is by far the most common reason emergency lighting stops working. Every self-contained emergency luminaire contains a rechargeable battery — typically nickel cadmium (NiCd) or nickel metal hydride (NiMH) — that charges continuously from the mains supply and discharges when the mains fails.
Why Batteries Fail
- Age — most emergency lighting batteries have a useful life of around four years, though some manufacturers claim longer. After this point, the battery can no longer hold sufficient charge to power the luminaire for the required duration (typically one or three hours).
- Heat exposure — batteries degrade faster in warm environments. Luminaires installed near heating systems, in ceiling voids with poor ventilation, or in south-facing areas can experience accelerated battery degradation.
- Deep discharge cycles — if the mains supply is interrupted frequently (for example, due to unreliable power supply or repeated testing without adequate recharge time), the batteries undergo more charge-discharge cycles and wear out faster.
- Manufacturing defects — occasional batch defects can cause premature failure, though this is less common with reputable manufacturers.
Warning Signs
- Luminaire dims noticeably during monthly functional tests
- Unit fails to illuminate at all during a test
- Battery appears swollen or is leaking
- Luminaire emits a burning smell
Prevention
- Replace batteries proactively on a four-year cycle, rather than waiting for them to fail
- Use quality replacement batteries specified by the luminaire manufacturer
- Allow adequate recharge time (minimum 24 hours) between tests
- Monitor environmental conditions and relocate units away from heat sources where practical
Common Cause 2: Lamp Failure
While LED technology has significantly reduced lamp failure rates in modern emergency luminaires, many older installations across Manchester still use fluorescent or tungsten halogen lamps. These have a finite life and will eventually fail.
Why Lamps Fail
- End of rated life — fluorescent tubes typically last 8,000–15,000 hours, while LED sources can exceed 50,000 hours. Once the lamp reaches end of life, the luminaire will not produce light regardless of battery condition.
- Incorrect lamp type — replacing a lamp with an incorrect wattage or type can cause premature failure or reduce light output below the minimum required by BS 5266-1.
- Vibration damage — in industrial environments or buildings near railways and busy roads, vibration can damage filament-based lamps and loosen connections.
Prevention
- Upgrade to LED emergency luminaires where possible — this dramatically reduces lamp failure rates and energy consumption
- Use manufacturer-specified replacement lamps when replacing failed units
- Include lamp inspection as part of your monthly testing routine
- Budget for a phased LED upgrade to eliminate lamp failure as a risk factor
Common Cause 3: Wiring and Connection Faults
Electrical faults in the wiring that supplies and controls emergency lighting can cause partial or complete system failure. These faults are often hidden within ceiling voids, trunking and containment, making them difficult to detect without specialist testing.
Why Wiring Fails
- Deterioration over time — older cable insulation (particularly rubber and early PVC types found in pre-1970s Manchester buildings) can become brittle and crack, leading to short circuits or open circuits
- Rodent damage — rats and mice chew through cable insulation, causing faults. This is a particular risk in older buildings with accessible ceiling and floor voids
- Water ingress — roof leaks, burst pipes and condensation can damage wiring and connections, especially in cable terminations and junction boxes
- Poor installation quality — loose connections, inadequate cable support and incorrect cable types can all lead to premature failure
- Subsequent building work — cables can be damaged during refurbishments, partitioning work or other trades working in ceiling voids
Warning Signs
- Multiple luminaires on the same circuit failing simultaneously
- Intermittent operation of individual units
- Tripping of the emergency lighting circuit breaker
- Visible damage to cables or containment
Prevention
- Include wiring inspection as part of your periodic EICR (Electrical Installation Condition Report)
- Protect cables from rodent damage using appropriate containment
- Brief other contractors about emergency lighting cable routes before any building work
- Address water ingress promptly to prevent secondary damage to electrical systems
Common Cause 4: Control Gear and Driver Failures
Modern emergency luminaires contain electronic control gear (drivers) that manage the charging of the battery and the switching between mains and emergency modes. Like all electronic components, these can fail.
Why Control Gear Fails
- Component ageing — electrolytic capacitors within drivers have a finite life, typically 8–12 years, and can cause driver failure as they dry out
- Power surges — voltage spikes on the mains supply can damage sensitive electronic components
- Overheating — poor ventilation around the luminaire can accelerate component degradation
- Manufacturing quality — cheaper luminaires may use lower-quality components that fail sooner
Warning Signs
- Luminaire charges indicator light not illuminating (if fitted)
- Unit switches to emergency mode randomly while mains is present
- Audible buzzing or humming from the unit
- Luminaire fails to switch to emergency mode during testing despite a good battery
Prevention
- Install surge protection on the emergency lighting circuit
- Ensure adequate ventilation around all luminaires
- Specify quality luminaires from reputable manufacturers when installing or replacing
- Plan for whole-unit replacement after 10–15 years of service
Common Cause 5: Poor Maintenance and Testing Practices
Perhaps the most preventable cause of emergency lighting failure is simply a lack of proper maintenance. Systems that are not tested regularly will develop faults that go undetected until a real emergency occurs — or until a fire risk assessor discovers the problem.
Why Maintenance Fails
- No testing regime in place — surprisingly common, especially in buildings where responsibility is unclear or where there has been a change of management
- Testing carried out incorrectly — monthly tests must simulate a mains failure to verify that each luminaire activates. Simply looking at the units while the lights are on tells you nothing.
- Annual duration test skipped — the three-hour (or one-hour) duration test is the only way to verify that batteries can sustain the required illumination period. Many building managers skip this test because it is disruptive.
- No records kept — even if testing is carried out, the fire authority expects to see documented evidence. Without records, you cannot demonstrate compliance.
Prevention
- Appoint a responsible person for emergency lighting testing within your organisation
- Use a professional testing service if you lack in-house capability
- Implement an automated test system (ATS) for larger installations — these can carry out and record tests automatically
- Keep a dedicated logbook or digital record for all test results and maintenance
Central Battery Systems vs Self-Contained Units
Commercial buildings may use either self-contained emergency luminaires (each with their own battery) or a central battery system (one large battery bank powering multiple luminaires via dedicated wiring).
Self-Contained Units
- Advantages: Simpler to install, no additional wiring required, failure of one unit does not affect others
- Disadvantages: More individual batteries to maintain, higher long-term maintenance burden, battery replacement required for each unit
- Best for: Smaller buildings, simpler layouts, buildings where cost is a primary consideration
Central Battery Systems
- Advantages: Centralised maintenance, easier battery monitoring, longer battery life (typically 8–10 years), can power more luminaires from one location
- Disadvantages: Higher initial cost, requires dedicated wiring, single point of failure (mitigated by monitoring), more complex installation
- Best for: Larger buildings, complex layouts, premises where maintenance efficiency is important
When to Replace Your Emergency Lighting System
There comes a point when repairing individual components is no longer cost-effective, and a full system replacement makes better sense. Consider replacement when:
- The system is more than 15 years old and experiencing frequent failures
- Spare parts are no longer available for your luminaire type
- The system uses obsolete technology (such as fluorescent tubes) that can be replaced with more efficient LED alternatives
- A fire risk assessment or BS 5266 survey identifies fundamental design deficiencies
- The cost of ongoing repairs exceeds the cost of a planned replacement programme
Manchester-Specific Considerations
- Older commercial stock across Manchester city centre, Salford, Stockport and surrounding boroughs often contains emergency lighting installed in the 1980s and 1990s that is now well beyond its expected service life
- Converted industrial buildings in areas like Ancoats, the Northern Quarter and Salford Quays may have emergency lighting that was designed for the original use and is no longer appropriate for the current occupancy
- Greater Manchester Fire and Rescue Service routinely checks emergency lighting during enforcement visits and has taken action against building owners with non-functional systems
- Climate considerations — Manchester's damp conditions can contribute to water ingress issues that affect emergency lighting wiring, particularly in buildings with flat roofs or poor weatherproofing
Get Your Emergency Lighting Checked
Do not wait for a failure or a fire risk assessment to discover problems with your emergency lighting. Manchester Compliance can carry out a full survey of your system, identify any issues and provide a clear plan to bring everything up to standard.
Contact us today:
- Phone: 0161 706 0244 (Monday–Friday, 8:00 AM – 5:00 PM)
- Email: hello@manchestercompliance.co.uk
- Emergency line: 0161 706 0244 (24/7 for urgent safety issues)
- Address: 25 Holden Clough Drive, Ashton-under-Lyne, OL7 9TH