Emergency lighting

Emergency lighting is provided when the supply to the normal lighting fails. It helps people to see their way and move to evacuate quickly to a safe place out of the building. It also avoids panic, restores confidence and enables specific tasks to be made safe.

Emergency lighting should be provided in all areas where, when the normal lights fail, there is insufficient daylight or borrowed light available for those people on the premises.

A risk assessment should be made to identify the places and routes where people may be at risk and need evacuating in the event of the normal lighting failing.

An emergency lighting scheme should be designed with sufficient consideration to the type of premise, size, complexity, kind of activities and type of people involved. Special consideration should be given to places where the elderly and those with disabilities may be present.

There are four main points to consider for an effective emergency lighting scheme:

1 – Exit Signage

Visible safety signs and signage to indicate the escape route and final exit should be available at all material times (luminance of the sign’s safety colours must be at least 2 cd/

m²). The escape route signs must be located so that occupants from any part of the premises can see and identify the direction for evacuation.

2 – Mandatory Points

Emergency luminaires have to be carefully positioned to ensure a compliant emergency lighting scheme. To provide adequate illumination they need to be mounted close to potential hazards on the route, such as stairs, a change of direction or crossings and places requiring emphasis, such as first aid posts, fire fighting appliances and marshalling points. Also for places where people may need reassurance in the event the normal lights failing, such as lifts, toilets or closets.

3 – Illumination levels and infill lighting In addition to the lighting of mandatory points, infill luminaires may be required to achieve the correct lighting levels.

An adequate level of illuminance on the floor of escape areas (minimum 0.5 lx) and escape routes (minimum on centre line 1.0 lx) should be made available within 5 seconds of the mains failing to avoid anxiety, and remain operative for at least 1 hour, or longer if required, for safe evacuation. Additionally take care to illuminate the volume of space (from floor up to a height of 2.0m) through which people move during evacuation by mounting luminaires above head height.

High-risk task areas should be illuminated to an adequate level (minimum 15 lx) within 0.5 seconds of the normal lights failing for as long as required to complete making the task safe or whilst people pass by if it is by the escape route.

Illumination should be carried out with light sources having a colour rendering index of at least Ra 40 so that safety colours in an escape area or on an escape route can be seen and discriminated.

Stylish luminaires should be chosen to blend in with the design of the overall lighting scheme, but they must suit the environmental conditions of the location. For example use IP65 emergency lighting luminaires outside the final exit. The luminaires may be dedicated standalone types or integrated into standard lighting luminaires. They can be self-contained or central power fed depending on the size and complexity of the premises, the operation and servicing and practicalities and through life economics of the installation.

4 – Maintenance and testing

Once the scheme is installed and commissioned, it is essential that the luminaires are properly maintained and ready to perform in the event of an emergency. To make sure installed emergency products are always fit for purpose, regular testing has to be conducted by the building operator. Therefore consideration should be given at the design stage to the intended method - be it local switch, automatic self-testing or an automatic

Specific Techniques

Emergency lighting system considerations Standby lighting is used as an alternative to normal lighting but it can also form the emergency escape lighting solution. When it does it must follow the rules governing escape lighting.

Escape lighting covers the need for clearly defined escape routes in the premises formed by corridors or paths indicated by painted lines. Open areas are defined as places where there is no clear route or where the routes are changing such as a large shop, open plan office or multi purpose hall. A high-risk task area is where some uninterruptible activity is ongoing, such as a chemical dip process, or some other process that requires unbroken lighting conditions for safe shut down. In some places where there is high risk of smoke accumulation (airlines, passenger ships) low location way guidance systems are provided to supplement the escape route lighting.

Emergency Lighting

Open area (anti-panic) lighting Emergency escape lighting

Low location way guidance

Standby lighting

High risk task area lighting Escape route lighting

Fig. 6.18 Specific forms of emergency lighting

Clearly defined escape routes

Clearly defined escape routes are taken to be up to 2m wide.

Here the horizontal illuminance at floor level on the centre line should be not less than 1 lux, and the centre band of at least 50 per cent of the route width should be illuminated to at least half the centre line value. The diversity of illuminance should not exceed 40:1. Wider routes may be treated as 2m wide strips of escape routes but preferably as open areas. The design illuminance is to be provided within 60 seconds, but preferably within 5 seconds of the supply failure. To avoid dazzling people it is important not to exceed the intensity limits related to the mounting height of the luminaires.

Safety signs

Strategically placed signs permanently indicating the escape directions from the premises are essential to alleviate anxiety and confusion by the people present. The signs should conform to the graphic design, colour and luminance criteria given in the EN1838 standard. It is important that during an emergency only signs that give a positive indication to the way out should be illuminated and that the signs are mounted high enough (above 2.0m) so that they are not obscured.

Open areas

Areas where the furnishing or equipment on the floor is frequently reconfigured will not have clearly defined escape routes and are therefore treated as open areas, as defined above.

In these the illuminance on the floor should be a minimum 0.5 lux anywhere up to 0.5m from the walls and 50 per cent should be provided within 5 seconds, 100 per cent being provided within 60 seconds of the normal lights failing. The diversity of illuminance should not exceed 40:1. To avoid dazzling people the intensity limits for the luminaire should not be exceeded for the mounting height in the scheme.

Exit signs should be located so that they are visible from any part of the space. not less than 1.0 lx along centreline not less than 0.5 lx

50% of width not less than 0.5 lx

Fig. 6.19 Escape route plan (up to 2m wide)

Specific Techniques

High risk task areas

During the failure of the normal lighting supply, emergency lighting is required in places where machinery, plant or other processes may present a hazard if left in operation, and that must be shut down before evacuating the area, In some cases the escape route may be alongside these hazardous tasks and therefore needs to be highlighted. There are also places where the task activity cannot be halted and needs standby emergency light (such as in an operating theatre).

The high risk tasks areas should be illuminated as required by the task and in any event the maintained illuminance should be not less than 10 per cent of the required maintained illuminance for that task and should not be less than 15 lux and be available in full within 0.5 seconds. The uniformity should not be less than 0.1. For this a no-break or maintained system should be considered.

Power systems for emergency lighting

Emergency lighting systems are usually powered from batteries or generators that are automatically triggered by a detection system as soon as the mains system fails. The system duration or category is defined by the period the system is able supply power to the load. Usually given as 60 minutes (1 hour) or 180 minutes (3 hours). The two main types of electrical systems in use are self-contained and central power:

Self-contained systems

Each luminaire is equipped with battery, charger, indicator and changeover device. These elements may be integral to the luminaire or housed in a separate unit mounted less than 1m from the luminaire. The mains supply charges the battery, which cuts in when the mains system fails. Self-contained systems are easy to install and extend, and require minimal maintenance.

The system may include a self- testing facility that can carry out the routine monthly and annual operational tests and give local indications of the status. They can also be connected to a central managed automatic testing system and can give printed report of any defects.

Each luminaire is equipped with batteries and inverter to power one lamp on mains failure

The gear may be remote mounted, if so the box should be within 1m of the luminaire.

Fig. 6.21 Self-contained system

Mains mode Emergency mode

mains lamp is on emergency lamp is on

Central systems

Here the power is provided by remote central batteries or generators and is distributed through sub-circuits to a number of slave luminaires. These systems are best suited for large premises. They will require space to house the large battery sets or generator. The wiring of the sub-circuits has to be protected and be of high-integrity. During design due allowance should be made for voltage drops. As part of the high integrity considerations the luminaires with loop-in/out wiring facility must also have protected glands and terminal blocks, alternatively the luminaires may be treated as an individual spur connection to a protected emergency power ring sub-circuit.

The system must include monitoring of the mains supply and detection of failure of local circuits in each part of the premises to bring on the emergency lighting.

Mains mode Emergency mode