Emergency lighting is lighting for an emergency situation when the main power supply is cut and any normal illumination fails.  The loss of mains electricity could be the result of a fire or a power cut and the normal lighting supplies fail. This may lead to sudden darkness and a possible danger to the occupants, either through physical danger or panic.

Emergency lighting is normally required to operate fully automatically and give illumination of a sufficiently high level to enable all occupants to evacuate the premises safely. Most new buildings now have emergency lighting installed during construction; the design and type of equipment being specified by the architect in accordance with current Building Regulations and any local authority requirements.

The Irish Standard provides the emergency lighting designer with clear guidelines to work to.

IS3217 2013 embraces residential hotels, clubs, hospitals, nursing homes, schools and colleges, licensed premises, offices, museums, shops, multi-storey dwellings, etc. Although this standard recommends the types and durations of emergency lighting systems relating to each category of premises, it should be remembered that the standards are the minimum safe standards for these types of building and that a higher standard may be required for a particular installation.

What is Emergency Lighting?

Lighting that automatically comes on when the power supply to the normal lighting provision fails.

Emergency lighting is a general term and is sub-divided into emergency escape lighting and standby lighting.

Emergency escape lighting – that part of an emergency lighting system that provides illumination for the safety of people leaving a location or attempting to terminate a potentially dangerous process beforehand. It is part of the fire safety provision of a building and a requirement of The Fire services Act 1981.

Standby lighting– that part of an emergency lighting system provided to enable normal activities to continue substantially unchanged. This guide does not include standby lighting as it is not a legal requirement and is a facility that may or may not be needed, depending on the use and occupancy of the premises, etc.

Emergency escape lighting is itself sub-divided into escape route lighting, open area lighting and high risk task area lighting.

Escape route lighting – that part of an emergency escape lighting system provided to ensure that the means of escape can be effectively identified and safely used by occupants of the building.

 

Emergency Exit Light

Open area lighting (in some countries known as anti-panic lighting) – that part of an emergency escape lighting system provided to minimise panic and ensure there is sufficient illumination to allow the occupants of a building to reach a place where an escape route can be identified.

 

Bulkhead emergency lighting

High risk task area lighting – that part of an emergency escape lighting system that provides illumination for the safety of people involved in a potentially dangerous process or situation and to enable proper shut-down procedures for the safety of the operator and other occupants of the premises.

Consultation and Design

The first stage of installing emergency escape lighting is consultation and design. The designer, responsible person and fire risk assessor should meet and decide where the escape lighting is required and mark up a plan showing the areas to be covered, the type (power supply), mode of operation, facilities and duration.

Type (power supply)

Self-Contained – Single Point

Advantages:

• The installation is faster and cheaper
• Standard wiring material may be used. Failure of mains supply due to cable
• burn-through will automatically satisfy the requirement for a luminaire to be lit
• Low maintenance costs – periodic test and general cleaning only required
• Low hardware equipment costs – no requirement for extended wiring, special ventilation etc.
• The integrity of the system is greater because each luminaire is independent of the others
• System can easily be extended with additional luminaires
• No special sub-circuit monitoring requirements

Disadvantages:

• The environmental conditions will vary throughout the system and batteries may be adversely affected by a relatively high or low ambient temperature
• Battery life is limited to between 2 and 4 years, dependent upon the application
• Testing requires isolation and observation of luminaires on an individual basis

In general, the decision to use either a central battery or a self-contained system is likely to be cost determined. If an installation has longevity and low maintenance as priorities, then the higher cost of a central battery may be acceptable on a very large project. Typically, luminaire and installation costs are a major consideration, particularly on smaller jobs, and it is this criterion which makes the self-contained luminaire the most popular choice.

Central Battery Source

Advantages:

• Maintenance and routine testing is easier, with only one location to consider
• The life of a battery is between 5 and 25 years, dependent upon type
• Environmentally stable in a protected environment; the luminaire can operate at relatively high or low ambient temperatures
• Large batteries are cheaper per unit of power and luminaires are usually less expensive

Disadvantages:

• High capital equipment costs
• The cost of the installation and system wiring is high because fire resisting cable like MICC or Pirelli FP200 type is required to each satellite luminaire
• Poor system integrity – failure of battery or wiring circuit can disable a large part of the system
• A requirement for ‘battery room’ to house cells and charger circuits, etc.; ventilation of acid gases may also be needed
• Localised mains failure may not trigger operation of emergency lighting in that area
• Voltage drop on the luminaire wired furthest from the central battery could become a problem

Mode of operation

Maintained or non-maintained is the principal consideration, which is decided by the use of the premises.

Maintained emergency luminaire: a luminaire in which the emergency lighting lamps are on at all times.

Maintained mode is generally used in places of assembly such as theatres, cinemas, clubs and halls; the full list is contained in IS 3217 2013. The lights are typically dimmed when these premises are occupied and the emergency escape lighting prevents total darkness.

Non-maintained emergency luminaire: a luminaire whose emergency lamps only come on when the power supply to the normal lighting fails. Non-maintained is the typical mode in a workplace or similar environment in which artificial lighting is normally deployed while the premises are occupied.

Combined emergency luminaire: a luminaire containing two or more lamps, at least one of which is energized from the emergency lighting supply and the other(s) from the normal lighting supply. A combined emergency luminaire can be either maintained or non-maintained.

Compound self-contained emergency luminaire: a luminaire providing maintained or non-maintained emergency lighting and also the emergency power supply to a satellite luminaire.

Satellite emergency luminaire: a luminaire for maintained or non-maintained operation and which derives its emergency operation supply from an associated compound self-contained emergency luminaire.

Facilities

A) Luminaire including test device: the luminaire contains a self-test module for testing purposes.

B) Luminaire including remote test device: the system is tested remotely by a centralised panel.

C) Luminaire with inhibiting mode: a control mode used to inhibit the emergency lighting luminaire from operating, thus preventing the discharge of the emergency lighting batteries at times when the building is unoccupied. If a mains failure occurs at such a time, the batteries will remain fully charged so that the building can be occupied when required. It is performed by an inhibitor switch that must be interfaced with other building services so that the premises cannot be inadvertently occupied without the emergency lighting being recommissioned.

D) High risk task luminaire: for risk task area lighting in areas of high risk, the maintained luminance shall not be less than 10% of the required maintained luminance for the task under normal lighting conditions. This will be subject to a minimum luminance of 15 lux. The uniformity ratio for task area lighting should be a minimum of 10:1 (0.1). The minimum duration shall be the period for which the risk presents to occupants.

Duration in minutes

The time required to evacuate the premises depends on their size and complexity. The duration itself is dependent not only on evacuation time but also on whether the premises are evacuated immediately the power and normal lighting fails and / or are reoccupied immediately the supply is restored. The minimum duration of an emergency escape lighting system is 1 hour.

A minimum duration of 3 hours should be used for emergency escape lighting if the premises are not evacuated immediately, as in the case of sleeping accommodation, for example, or if the premises will be reoccupied immediately the supply is restored without waiting for the batteries to be recharged.

One hour’s duration should only be used if the premises are evacuated immediately on supply failure and not reoccupied until full capacity has been restored to the batteries.

IS 3217 2013 contains detailed information on the recommended duration of systems in various premises.