Feature
1838: 2013, defines the minimum lux levels and photometric requirements when designing the emergency lighting scheme. Also, in place is the standard; BS EN 60598-2-22: 2014, for luminaires used in emergency lighting and ensures that they achieve the performance required whilst remaining electrically and mechanically safe. In addition, the European Application
Standard with improved testing regimes, EN 50172: 2004, is a vital supporting part of the BS 5266 series. The design objective for any
emergency lighting system is established by BS 5266 Section 5.2.1 which says that, when the supply to the normal lighting fails, emergency lighting is required to: • indicate clearly the escape routes • provide illumination along such routes to allow safe movement through the exits
• ensure that fire-alarm and fire- fighting equipment can be readily located
British and European Standards
provide guidance on the implementation of requirements and solutions, on sustainability and energy use, guidance on required equipment, lighting for specific specialist areas as well as guidance on the installation process, testing and commissioning – all of which need to be considered at the start of the design process. It is also important for the manufacturer
to understand the intended environment for the luminaire in order to specify the correct safety components. Although there is currently no legislation covering the use of LS ZH (low smoke, zero halogen) components, it is recommended that LSZH be used in fittings specified for use in large public areas where there is a risk of fire. This will minimize the risk from the after effects of an electrical fire, such as gas and
smoke inhalation. For example, after the Kings Cross fire in 1987, LSZH sheathing became mandatory for all electrical wiring in London Underground Stations.
Compliance
In order for the emergency lighting system to remain compliant throughout its lifetime, structured and effective maintenance is essential. The system requires testing in line with the requirements specified in BS EN 50172, together with any remedial action which is identified by these tests. Routine visual inspection of the system is also fundamental to check for any changes to décor, colour schemes, fabric and structure together with any reparations which may impact the designed scheme. Unlike a fire alarm system which is generally subjected to a simple, periodic audible test for functionality, (albeit in line with an annual sub-contracted service contract), the maintenance of the emergency lighting system is more time consuming if being undertaken manually, without the aid of an automatic test facility, The annual full discharge test of up to three hours duration may need to be staggered across different storeys and areas within the building and this may be perceived as a costly and labour intensive overhead. What value can be put on the health and safety of occupants though? The effect of the emergency lighting is seldom seen until required, and it is during these times, where the safe and immediate evacuation of the building is paramount, that we come to appreciate the true value of this safety critical system.
Luminaires
The cumulative operating costs of emergency lighting can be considerable, and the choice of fitting should be considered in terms of its installation cost, long-term energy consumption and maintenance or replacement costs. LED’s consume about 25% of the power of traditional lamps and offer excellent lumen maintenance as the light output remains constant throughout its design life. The greatest cost benefit, however, relates to lamp replacement. LED lamps typically have a 50,000h rated life, ten times that of a typical fluorescent tube. Using LED emergency luminaires will greatly reduce the maintenance costs of an emergency lighting system and they have a longer expected life and lower running costs than standard luminaires.
Batteries
Batteries also have an impact on the cost of luminaires intended for emergency lighting, with Nickel- cadmium (NiCd) batteries the preferred choice for self-contained
luminaires despite the fact that they utilise a toxic metal. However, Nickel-Metal Hydride (NiMH) batteries offer a viable alternative with significant benefits over the Nickel-cadmium battery. The NiMH battery offers an energy density two to three times that of the NiCd battery, meaning it can be a third of the size of the NiCd equivalent. Combined with a LED light source and appropriate charger, this can result in a very compact package. Another significant benefit is the charging regime. NiCd batteries require a constant current charge, NiMH batteries however, have an excellent rapid-charge capability meaning they can be given a boost charge followed by a trickle charge. This results in long term energy savings, reducing ongoing costs.
Testing
Statistical evidence indicates that regular testing and maintenance of emergency lighting systems is not routinely carried out by many organisations as it is laborious and time consuming, and therefore expensive. However, the fines for non-compliance are more so and eventually puts lives at risk. Testing of the emergency lighting system
should be carried out at regular intervals by a qualified person. The tests must be carried out in line with the schedules outlined in BS EN 50172 as below: • Daily – visual check that all charge indicators are lit on and check lamps on all maintained luminaires are working. • Monthly – a monthly functional test Continued on page 30
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