The great escape

Entitled Lighting applications – emergency lighting, this standard applies the best practice principles that have long been encouraged and promoted by the Industry Committee for Emergency Lighting (ICEL).

This European standard is the same as BS 5266 Part 7: 1999 and is especially important because it raises these issues to the status of a Standard, as opposed to the former Code of Practice.

Possibly the most far-reaching changes this standard creates relate to the required levels of illuminance – the light level at floor level – measured in lux. It also introduces an additional area type category, defined as 'high-risk task areas', intended to encompass any location where human safety is risked by a dangerous process or situation if the normal lighting should fail.

Escape routes lighting
The standard states that a minimum level of one lux is required on the centreline of emergency escape routes, and that a minimum of 50% of that value should be achieved over at least half of the route width.

However, a special exception called an A-deviation has been included for the UK. Effectively this permits the former levels of 0·2 lux on the centreline and 0·1 lux minimum over 50% of the width to remain acceptable – as long as the escape route is permanently unobstructed.

In practice though, it is virtually impossible to guarantee that an escape route will never be obstructed – a temporarily-parked cleaner's trolley would count as an obstruction for the time it is there. Consequently, the majority of escape routes will have to be lit to the new standard of one lux – especially as any changes of level or direction must have a minimum level of one lux anyway.

Open areas illuminance
An open area is defined as a space of over 60 m2 where there is no fixed escape route and there are many ways around any possible obstacles to reach an identifiable escape route. In such areas, the standard requires over 0·5 lux at the floor level of the core area, excluding a 0·5 m border around the perimeter.

Most manufacturers that are involved with the ICEL scheme will be able to provide accurate spacing tables to achieve the required illuminance levels with their emergency lighting luminaires. ICEL accreditation includes independent verification of photometric performance and data.

High-risk task areas
The emergency lighting illuminance required for high-risk task areas is a minimum of 10% of the required maintained illuminance for the task or 15 lux – whichever is greater. Hence, if the task requires 500 lux on the working plane, the emergency lighting should provide at least 50 lux. The uniformity of the illuminance must be at least 0·1.

The other main consideration is that the emergency lighting levels must reach the required illuminance within 0·5 seconds – this may have a bearing on the light sources used for these areas. Light sources that take more than 0·5 seconds to warm up to maximum light output may have to be specified in relation to their light output at start-up.

The lighting for high-risk areas will often be most effectively provided by the conversion of selected mains lighting luminaires using high ballast lumen factor conversion kits. For larger areas, static inverter systems can be used to provide emergency power to selected mains lighting in the area.

It is important to recognise that a five-fold increase in illuminance levels on emergency escape routes does not mean that you have to fit five times as many emergency luminaires. Emergency lighting luminaires and the light sources they use have improved dramatically during the last decade or so and it will usually be possible to comply with the new standards with only a few extra.

For open areas, the change from a one lux average to a 0·5 lux minimum may require additional luminaires or emergency lighting conversions, but this will vary greatly with the shape of the space. In some cases there will be no change required.

All of these issues are covered in the ICEL 1006 Emergency lighting design guide, while the ICEL 1008 Emergency lighting risk assessment guide offers a practical and step-by-step guide to this increasingly important area. Further details can be found on the ICEL web site at www.icel.co.uk.