Introduction
Emergency lighting is self-descriptive - lighting in an emergency situation when the main power supply fails. The loss of mains electricity could be the result of a fire or a power cut, when the normal lighting supplies fail. This may lead to sudden darkness and a possible danger to the occupants, either through physical danger or panic.
Every type of emergency lighting system uses a battery, or alternatively, a generator that will provide electricity to the lights during a blackout. Today, emergency lighting is installed in virtually every commercial and high occupancy residential building.
Types of emergency lighting
There are three main types of emergency lighting systems:
1. Non-maintained - The emergency light units only illuminate in the event of a mains failure. (NM2 - Non-maintained System, emergency duration of 2 hours.)
2. Maintained - The emergency light units are illuminated at all times using the same lamps for both normal and emergency operation. (M3 - Maintained System, emergency duration of 3 hours.)
3. Sustained - The emergency light units are fitted with two lamps or two sets of lamps. One of which operates on mains 240V AC supply; the other which operates from the battery supply in the event of mains failure. It is basically a non-maintained system with the addition of mains lamps which should be illuminated whenever the premises are occupied. (S1 - Sustained System, emergency duration of 1 hour.)
The lighting systems incorporate single or pairs of incandescent bulbs, or one or more clusters of high-intensity light-emitting diodes (LED). The emergency lighting heads are usually either PAR 36 sealed beams or wedge-shaped base lamps.
All units have some sort of a reflector to focus and intensify the illumination that they provide. Many use a plastic cover over the fixture, or a reflector placed behind the light source to increase the light level.
Individual light sources can be rotated and aimed for where light is needed most in an emergency, for example, in the direction of fire exits. In order to reduce the size of the batteries and the load on the circuit into which the emergency lighting is wired, the latest systems operate at 6-12 volts.
The batteries used in modern emergency lighting are commonly lead-calcium which have a lifespan of 10 years or more on continuous charge.
When activated due to a blackout, the batteries are designed to keep the unit illuminated for at least 1 hour and up to 3 hours. As well as obviously being illuminated for safe evacuation of the building, it is more helpful if the emergency lighting remains on so that occupancy of the building can continue during a short power cut.
British Standard
Emergency lighting is normally required to operate fully automatically and give illumination of a sufficiently high level to enable persons of all ages to evacuate the premises safely as well as providing light for the emergency services to operate effectively.
Most new buildings now have emergency lighting installed during construction, the design and type of equipment is normally specified by the relevant local authority, architect or consultant.
The British Standard provides the emergency lighting designer with guide lines which form the general basis for the system designer and electrical contractor.
British Standard BS 5266: Part 1: 2005 is the relevant standard, including in its scope residential hotels, clubs, hospitals, nursing homes, schools and colleges, licensed premises, offices, museums, shops, and multi-storey dwellings.
Although this standard recommends the types and durations of emergency lighting systems for each category of premise, it should be remembered that these are the minimum safe standards for the types of premises. It is frequently appropriate to consider a higher specification in a particular installation.
Emergency Luminaires
An emergency luminaires are either self-contained, with all components integral to the luminaire body, (battery, charging circuit, mains ballast); or ‘slave’ to a central battery system with only the lamp, (and an inverter if fluorescent), within the luminaire body. The power supply in the event of failure being supplied to the luminaire.
The majority of systems installed in the United Kingdom are of the, former self-contained type.
How much light is provided?
BS5266 recommends the provision of a horizontal illumination at floor level on the centre line of a defined escape route, permanently unobstructed, of not less than 0.2 lux and 0.5 lux minimum for anti-panic areas and excluding a 0.5 metre border around the room.
In addition, for escape routes of up to 2m wide, 50% of the route width should be lit to a minimum of 0.1 lux. Wider escape routes can be treated as a number of 2m wide bands. The actual degree of illumination should be closely related to the nature of both the premises and its occupants. Electrical contractors pay special attention to illumination levels for old persons’ homes, hospitals, crowded areas, such as pubs, discos and supermarkets; and to whether or not the premises are residential.
Siting of luminaires and signs
Careful consideration will be given by your contractor to the siting of the lighting units and signs.
The units and signs should be sited to clearly show the exit routes leading to the final exits from the premises. Where an exit route or final exit is not readily identifiable, a sign should be utilized rather than a lighting unit.
Particular attention will be paid to individual stairways, changes in level, corridor intersections, changes in direction, and the outside of each final exit. Access to fire alarm call points, fire fighting equipment, should be clearly illuminated.
Your electrical contractor will be able to assist with detailed computer calculations or luminaire manufacturers' spacing tables.
Servicing and testing
Testing an emergency lighting system requires a mains power failure on the normal lighting circuit or circuits or individual luminaire's. This will force the emergency lighting system to operated and use the battery supply.
Manual Testing
A simulated mains failure can be provided by a switch to isolate all lighting circuits or individual circuits or individual luminaire's. If manual testing is utilised, the following points should be considered:
In a non-maintained system, a single switch is used for the whole building or a separate switch used for each circuit. This means to simulate the mains failure a complete tour of the whole system to check that all emergency luminaires are correctly operating is required.
When the mains supply is restored, another full tour is required to check that the batteries are recharging. If all luminaire's are individually switched, only a single walk around the building will be needed. However, the test switches can spoil interior decor building; and they must be of a type that is tamper proof.
After the tests, it is recommended that the performance of the system should be logged.
Automatic Testing
If the costs of an engineer’s time and the disruption caused by manual testing are considered excessive, automatic systems should be considered.
A typical automatic system consists of a main control panel, plus one remote unit per luminaire. The remote units report back to the main panel using the mains wiring in the premises.
The main panel can control up to 500 luminaire's and each remote unit can be configured to be maintained or non-maintained, three hour or one hour type and the frequency of tests can also be set.
All activities are logged at the main panel and can be printed on the system printer either continuously or on user request. Thus, a hard copy of when each unit was tested is always available together with log entries when either user or engineer modes are used.
Servicing
Regular servicing is essential and your electrical contractor will be able to provide detailed advice and guidance.
It is recommended that a Maintenance Contract is taken out for your emergency lighting which will provide two annual visits for systems to be thoroughly checked and tested.
A 'full discharge test' should be carried out annually. The emergency lights are activated and allowed to stay on until they go off, fully discharging the batteries. The timing of such tests is important, as the premises should not be occupied for the following 24 hours while the batteries are recharging.
For more information, contact Mace on 01283 511 726.
General information
Base guidance document
BS 5266-1- 2005 Emergency lighting-Part 1: Code of practice for emergency lighting of premises. Gives general rules and guidance on the provision and operation of emergency lighting in most premises other than dwellings.
Also additional information on servicing can be found in BS 5266 - Part 1 - 2005 Emergency lighting - section 13 servicing.
System standards
BS EN 1838:1999/ BS 5266-7:1999 Lighting applications - Emergency lighting. Specifies the illumination to be provided by emergency lighting (including luminance, duration and colour)
BS EN 50172:2004/ BS 5266-8:2004 Emergency escape lighting systems - Specifies the minimum provision and testing of emergency lighting for different premises
