Emergency Lighting

Robin Wright

 

  1930s fitting
  A 1930s fitting converted for use as a mains/emergency fitting

Emergency lighting almost invariably consists of ugly boxes fixed to ceilings and bulkheads. These fittings disfigure the corridors and spaces which form the escape routes in interesting modern and historic interiors alike. Yet there are perfectly effective alternatives which will satisfy fire safety requirements, including discreet modern fittings such as fibre optics. In historic buildings any early light fittings which survive can also often be adapted to provide a sympathetic solution.

IS PERMANENT EMERGENCY LIGHTING
REALLY NECESSARY?

The first question to ask is whether emergency lighting is really necessary at all. Very often members of the public will not be visiting a historic building after dark, or if they are it may be for a special concert or event which takes place infrequently.

If there is no public access to a historic building after dark and it is otherwise unoccupied, there may be no need to provide any emergency lighting. If, on very infrequent occasions, there are concerts or events, temporary emergency lighting must be considered and should be located at the exits of the room and on the fire escape routes.

The temporary emergency lighting could consist of non-maintained, three-hour, emergency exit box lights, which sit on the floor and are plugged into the nearest 13 amp socket outlet. When the temporary exit signs are not being used, a special plug-board should be provided so they can be charged all the time. Any such arrangement has to be authorised by the local fire officer.

Another method of providing temporary emergency lighting is by using hand torches. The ratio of members of staff with hand torches to members of the public must be high to satisfy health and safety regulations.

Emergency lighting required for regular use, however, may not be needed throughout the building and so could be restricted to one area. For example, if a ballroom is in frequent use during the winter but other areas are not, the provision of emergency lighting could be restricted to the ballroom itself, its fire escape routes, and any other rooms connected with its use.

HOW TO ADAPT EXISTING FITTINGS

Emergency lighting can be provided in many ways; it is not necessary to use the ice cream tub on the ceiling and standard emergency exit signs, which look incongruous in a historic building. A far more acceptable solution is to use as many of the existing historic luminaires as possible.

The British Standard for emergency lighting of premises other than cinemas and certain other specified premises used for entertainment states that the illumination level along the centre line of the escape routes should not be less than one lux. As this is so low, a suitable level can be achieved without any photometric data for the existing luminaires simply by over-lighting the escape routes.

One of the most comprehensive methods of providing emergency lighting is by the use of a standby battery inverter unit, which enables the existing historic luminaires to be utilised. The luminaires required for emergency lighting are all wired from the same distribution board. A feed is taken from the standby battery inverter unit to the distribution board, and the lighting circuits are wired through a special relay unit to the various lighting points. Using the relay unit enables ordinary light switches to be used to operate the emergency lights just like normal lights, but when the power fails the emergency lights will be illuminated regardless of whether the switch is on or off.

The feed from the inverter unit to the distribution board, from the distribution board to the relay unit, and the circuit wiring, must of course be as fireproof as possible, and it is preferable to use MICC/PVC cables which give a very high degree of electrical integrity. The last thing you want is for the fire to burn through the cables causing the emergency lights to fail. This way the emergency lights will last for the full three hours duration.

The exit signs can be temporary or permanent. It is perfectly acceptable to have pieces of stiff cardboard painted with the standard emergency exit legend and located above the exit doors, provided there is an emergency light near enough to the door to provide the correct amount of illumination on the sign. In the same way, an emergency light can be located in all the necessary locations detailed in BS 5266.

With this method of emergency lighting all the luminaires are the same, and the aesthetic appearance of the historic building is preserved.

An alternative method is the use of remote, self-contained emergency battery packs which can be non-maintained, maintained, or sustained, depending upon the task at hand. The remote emergency battery pack must be located within one metre of the emergency fitting and the wiring between them must also be fire-resistant, to allow the emergency light to be illuminated continuously for the full three hours duration in the event of a fire.

Remote, self-contained emergency battery packs can be used to power a variety of different types of emergency fittings, for example: low-voltage, 50 watt dichroic down-lighters; table lamps where the remote emergency gear is located under the table; existing historic luminaries; and a whole range of special luminaires designed for a particular project, where the remote emergency control gear box is located in a convenient store, a ceiling or wall void. Access must be provided for maintenance of the remote control gearbox. Depending on the type of gear box used the luminaires can be switched on and off as normal, but when the power fails the emergency light will illuminate for the full three hours discharge time.

When using this type of gear pack it is very important to ensure that the red neon is mounted in a visible position on the luminaire as a visual check that the gear pack batteries are charging. There must also be maintenance access to the gear pack and sufficient ventilation to prevent the batteries overheating.

Another method of concealing emergency lighting is to install new, self-contained emergency luminaires within existing ones, thus keeping the ordinary, emergency and mains luminaires all the same. Many manufacturers supply both emergency and mains luminaires of the same design. Consideration must again be given to ventilation to prevent the batteries from overheating. If existing historic luminaires are to be converted to contain the emergency battery pack and control gear, they must be tested in accordance with the ICEL Technical Guide 1004, which can be downloaded from the Industry Committee for Emergency Lighting website, www.icel.co.uk.

INTRODUCING NEW EMERGENCY LIGHT FITTINGS DIRECTLY

Fibre optic lighting can also be used as emergency lighting, with fibre optic cables concealed above the skirting boards along a corridor to light the floor. However, concealing the cables can be very difficult if the walls are not being plastered as part of the building works, and setting the correct angle can be a challenge. Fibre optic cables can also be taken up the walls to door height level to light cardboard exit signs temporarily mounted above the exit doors.

Fibre optic emergency lighting systems can be virtually invisible as the fibre optic cables used are only a few millimetres in diameter. However, the design and installation of the system must comply with BS 5266-2 1998, BS 5266-4 1999 and BS 5266-5 1999, which can make it difficult to achieve the concealment and levels of illumination required. Various companies provide computer programs to calculate the level of illumination achieved by different types of fibre optic cables.

Many refurbished churches are being converted into multi-functional buildings with a variety of uses such as concerts, nativity plays, meetings and play groups, all requiring the use of emergency lighting. While it is often impractical to provide an overall level of illumination as required by BS 5266, it is sometimes possible to provide suitable emergency lighting under galleries.

Provision for emergency exit signs can be made above the exit doors by installing a neat two amp, three-pin socket outlet so that a self-contained emergency exit sign can be plugged in above the door. The sign can be held in place by small cup hooks above the door, then taken down after the event and kept charged on a special plug-board, plugged into a 13 amp socket outlet in a store room.

If an exit route is through a vestry, the vestry can be lit using a fluorescent fitting with a built-in emergency battery pack. Emergency lighting outside the emergency exit doors is also required in accordance with BS 5266.

It is essential that all the emergency lighting cables and equipment are installed very carefully to ensure that the installation is completely invisible and does no harm to the existing historic structure. It is also advisable to plan the installation in such a way that it can be removed at a later date should the use of the building change. For example, if it is unavoidable to run cables on the surface of a fair-face stone wall, all the fixing for the cables should be within the mortar joints between the blocks of stone, and the colour of the sheath of the cable must match the surface upon which it is being run. This way, if the cable ever needs to be removed, the damage could be repaired by repointing the mortar joints, whereas if the cable had been fixed into the stone blocks any damage could never be completely concealed.

Installation often entails the involvement a number of different people who must be consulted about the location and installation of the emergency luminaires within the constraints of the historic building and the current British Standards. Often their requirements will conflict with one another!

The illustrations give examples of what can be done with a little thought in order to fulfil both aesthetic and safety requirements within the constraints of a historic building. Above all, one must comply with the requirements of the British Standards and obtain the local fire officer’s authority and approval for the method of emergency lighting adopted, especially if the client requires a licence for the activities within the historic building.

 

 

 

This article is reproduced from The Building Conservation Directory, 2002

Author

ROBIN WRIGHT is Senior Associate of Lightwright Associates, Building Services Consulting Engineers, Lymm, Cheshire.

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