Emergency Lighting Systems: Self-Contained vs Central Battery, Durations and Exit Signs

Emergency lighting is the part of a lighting installation that must work when everything else has failed. When the normal supply is lost, it has to light escape routes, open areas and dangerous tasks well enough for people to move safely, and it has to show clearly where the exits are. The system architecture, whether self-contained luminaires or a central battery, shapes how that is achieved, how it is tested and how it is maintained.

This article answers the question: How do self-contained and central battery emergency lighting systems compare, and what should a specification state about modes, durations, exit signs and testing?

What emergency lighting covers

The terms below follow international usage, including ISO 30061 (CIE S 020):

• Escape route lighting lets people identify and use escape routes safely.
• Open area (anti-panic) lighting gives enough light in larger spaces for people to reach an escape route without panic.
• High-risk task area lighting lets people make a dangerous process or situation safe before leaving, for example shutting down machinery.
• Standby lighting is not escape lighting. It lets normal activities continue during a supply failure, for example in hospital areas or control rooms, and is often supplied from a generator or UPS.

ISO 30061 states that designs should use worst-case conditions: minimum light output over the luminaire’s life, at the end of the rated duration, and counting only direct light, without reflections from room surfaces. This is different from normal lighting design, and it is the main reason why emergency lighting calculations differ from general lighting calculations.

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Operating modes

• Maintained. The emergency lamps are energised at all times when normal or emergency lighting is required: from the normal supply in normal operation, and from the battery or central emergency supply when the normal supply fails. Typical for exit signs and spaces where people are unfamiliar with the building.
• Non-maintained. The emergency lamps are in operation only when the supply to the normal lighting fails. Typical for escape route lighting in workplaces.
• Combined. A luminaire contains two or more lamps, at least one energised from the emergency lighting supply and the others from the normal lighting supply. IEC 60598-2-22 notes that a combined luminaire is either maintained or non-maintained; some markets call the maintained version “sustained”.

The mode affects energy use, the lamp’s operating hours and how the occupants perceive the space.

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Self-contained luminaires

A self-contained emergency luminaire contains its own battery, charger and control gear. It monitors the normal supply locally and switches to battery when that supply fails.

Advantages:

• Each luminaire has its own battery, charger and control gear, so a failure of these parts affects only that luminaire. A fault on the shared unswitched supply circuit or its protective device, however, affects every luminaire on that circuit: they all switch to battery operation. While the supply remains off they keep discharging, which reduces their remaining emergency operating duration (autonomy); the full rated duration is available again only after the supply is restored and the batteries have recharged.
• Installation uses normal lighting circuits and wiring.
• Systems are simple to extend and modify.
• No separate battery room is needed.

Limitations:

• Batteries are distributed across the building, so replacement and testing take place at every luminaire.
• Battery life depends on the temperature at each luminaire, which may be high in ceiling voids or near heat sources.
• Without automatic testing, checking every luminaire is labour-intensive.

Central battery systems

A central battery system supplies emergency luminaires from a central battery and charger, with changeover equipment and distribution through fire-resistant cables. Larger buildings may use several group or sub-central systems.

Advantages:

• Batteries are in one controlled location with stable temperature, which helps battery life and inspection.
• Luminaires are simpler and contain no batteries.
• Central monitoring of circuits and luminaires is straightforward.

Limitations:

• Wiring to each luminaire must keep working during a fire for the required time, so cable type and installation are critical. Circuit integrity of cables under fire is tested under the IEC 60331 series.
• A fault on a distribution circuit affects every luminaire on that circuit, and a fault in the central equipment or a main circuit can affect many luminaires, so redundancy and circuit design matter.
• A dedicated battery room or cabinet is needed, with ventilation and safety measures for the battery type. IEC 62485-2 gives safety guidance for stationary batteries.

In Europe, central power supply systems for safety equipment are covered by EN 50171, which is referenced in European practice.

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Comparison at a glance

Rated duration and recharge

Every emergency luminaire is marked with its rated duration: the time for which it provides emergency light after the normal supply fails. Rated durations of 1 hour and 3 hours are common. The required duration depends on the building type, its use and local rules. Where people may stay in the building after a supply failure, or re-occupation happens quickly, a longer duration is often needed.

Batteries also need time to recharge after a discharge. The luminaire standard, IEC 60598-2-22, specifies how rated duration and charging are tested. The specification should state the required duration and any recharge expectations rather than assume the product default.

Illuminance and luminaire placement

ISO 30061 sets out luminous requirements for escape route, open area and high-risk task area lighting, and for safety signs, including sign luminance, colour, uniformity and the relationship between sign height and viewing distance. Its values are minimums for design, calculated for the full rated duration and the end of the equipment’s design life. National regulations may set different values, so the design should follow the regulations in force where the building is located.

In addition to meeting average and minimum illuminance, emergency luminaires are typically positioned at points where people need to see hazards or safety equipment, for example:

• near each exit door and emergency exit;
• at changes of direction and intersections of corridors;
• near stairs, so that each tread receives direct light;
• near changes of floor level;
• near fire-fighting equipment, call points and first aid points.

Local regulations set the exact list.

Exit and safety signs

Exit signs tell people where to go. ISO 7010 provides internationally recognised safety sign symbols, including emergency exit signs that combine a running figure, a door and direction arrows, designed to the principles in ISO 3864-1.

Signs can be:

• Internally illuminated, where the light source is inside the sign. These are more readable in smoke and at a distance.
• Externally illuminated, where an emergency luminaire lights a printed sign.

The maximum viewing distance depends on sign height and on whether the sign is internally or externally illuminated; ISO 30061 relates sign height to viewing distance. Choose the sign size from the longest viewing distance on the route. Sign conventions differ between jurisdictions. Some require pictograms; others require text-based “EXIT” signs, sometimes in a specific colour. Specify the convention required at the destination.

Batteries and control gear

Battery chemistry influences design life, temperature tolerance and maintenance. Nickel-based and lithium-based chemistries are commonly used in self-contained luminaires; lead-acid and other chemistries are common in central systems. Temperature is critical: batteries in hot ceiling voids or plant rooms age faster. State the expected ambient temperature at the luminaire location.

Electronic control gear for emergency operation is covered by IEC 61347-2-7, which addresses DC-supplied electronic control gear for emergency lighting.

Testing and monitoring

Emergency lighting must be tested regularly to confirm it works and that batteries still achieve the rated duration. Options include:

• Manual testing, by simulating supply failure and inspecting each luminaire. This is labour-intensive in larger buildings.
• Self-testing luminaires, which carry out function and duration tests automatically and show status locally.
• Addressable systems, which report test results and faults to a central panel. Automatic test systems for battery-powered emergency escape lighting are covered by IEC 62034. Digital lighting control protocols such as DALI include emergency control gear (IEC 62386-202).
• Central battery monitoring, which supervises circuits and luminaires from the central equipment.

The required test frequency and records are set by local regulations and the building’s maintenance regime. Specify the testing method, data reporting and integration with any building management system.

Relationship with generators and UPS

A generator or UPS can supply standby lighting and may also support emergency lighting, but they do not automatically satisfy emergency lighting requirements. Generator start and changeover time, and the reliability of the transfer, must suit the emergency lighting response time, and local rules may require a separate emergency source for escape lighting. Critical Power Systems: Generators, UPS and ATS explains how those systems fit together. IEC 60364-5-56 covers supplies for safety services in LV installations.

Hazardous areas and harsh environments

Emergency luminaires in hazardous areas need Ex protection under the IEC 60079 series, and the protection concept and marking must match the area classification. Ex-rated emergency luminaires are project-specific items and should be specified separately from the general emergency lighting schedule. In outdoor, wet, dusty or corrosive locations, state the required IP rating, impact resistance and ambient temperature range.

IEC and ANSI/IEEE practice; 50 and 60 Hz

The IEC and ISO references above are used internationally. North American practice relies on different codes and product standards, with different requirements for exit signs, durations and testing. Use the rules of the destination and do not combine requirements from different systems. Emergency luminaires and central systems should be rated for the local supply voltage and frequency, whether 50 Hz or 60 Hz, and for the DC voltage of any central battery.

Specification and procurement considerations

An emergency lighting specification should include:

• the regulations and standards that apply at the destination;
• system type: self-contained, central battery or a combination;
• operating mode for each luminaire type: maintained, non-maintained, or combined (stating whether maintained or non-maintained);
• rated duration and recharge expectations;
• the luminaire schedule with photometric data based on emergency mode output;
• exit sign type, symbol convention, size and viewing distance;
• battery chemistry, design life and ambient temperature at installation locations;
• testing and monitoring method, reporting and interfaces;
• for central systems: battery and charger capacity, circuit design, fire-resistant cable requirements and the battery room;
• IP rating, impact resistance and any Ex requirements;
• supply voltage and frequency.

For specifying general luminaires, see Specifying LED Luminaires: Output, Optics and Controls. For environmental conditions, see Defining Site and Service Conditions. For presenting the enquiry, see Preparing an RFQ for Electrical Power Equipment.

Common specification mistakes

• Using normal-mode photometry for emergency calculations. Emergency output is usually lower, and calculations must reflect worst-case conditions.
• Specifying duration without considering occupancy. The required duration depends on how the building is used.
• Ignoring the ambient temperature at luminaire locations. High temperatures shorten battery life.
• Mixing exit sign conventions. Specify the convention required at the destination.
• Omitting the testing method. Without automatic testing, maintenance costs and the risk of undetected failures rise.
• Assuming a generator meets emergency lighting requirements. Check response time and local rules.
• Underestimating fire-resistant wiring for central systems. Cable type and installation are critical.

Conclusion

Self-contained and central battery systems can both deliver reliable emergency lighting. Self-contained luminaires suit smaller and dispersed buildings. Central systems suit larger buildings where centralised batteries and monitoring are worth the infrastructure. Define the system type, modes, duration, signs and testing clearly, and follow the regulations at the destination for the values.

Related AdepaTrade solutions

AdepaTrade sources indoor, industrial, outdoor and emergency lighting, with the controls and supply equipment around them, to project specifications. Ex-rated emergency luminaires are handled as project-specific items. Lighting & Infrastructure · Critical & Backup Power

Relevant standards

IEC and ISO standards are the primary international reference. Confirm the applicable edition for each project; national regulations set required values and testing regimes.