As of March 2013 the NEW European Standard BS EN 54-23 has become mandatory.
Normal hearing is taken for granted by most of us, but there are estimated to be nearly nine million people who are deaf or hard of hearing in the UK, equivalent to one person in every seven. For these people, reliance on audible alarms in the event of a fire is ineffective. In addition, increased concerns over health and safety are encouraging the greater use of ear defenders in the work place and so there is a sizeable contingent of people who work in environments where alarm sounders are unlikely to be heard.
To overcome these issues, signalling needs to be broadened to stimulate senses other than hearing. Supplementing audible alarms with visual alarm devices (VADs) is an effective way to warn people in or around a building of the occurrence of a fire emergency so that they can take appropriate action. Over recent years, the installation of VADs has experienced considerable growth and this trend continues due to the influence of the Equalities Act and their suitability for various applications including staff restricted warning systems, (such as nursing homes and public assembly buildings), broadcast studios and hospital operating theatres.
Current building regulations and BS8300, Design of buildings and their approaches to meet the needs of disabled people, recommends that a VAD is sited in any area where a deaf or hard of hearing person may be left alone e.g. toilets or bedrooms. This, alongside the rising awareness of the Equality Act 2010 highlights the increasing importance that the industry is vigilant in designing fire systems with the deaf and hard of hearing in mind.
BS EN54-23
Up until May 2010, there was no fire industry standard that determined the light output performance criteria and installation requirements of visual alarm devices. This gave rise to manufacturers specifying the performance of their products in an inconsistent, confusing and often misleading way. The use of Joules, Watts and Candela to specify a VADs performance are all largely meaningless, as they do not take into account the effectiveness of the light signal over a given area. Now this has been rectified with the release of standard BS EN54-23: Fire alarm devices – Visual alarm devices.
BS EN54-23 specifies the requirements, test methods and performance criteria for VADs in fire detection and fire alarm systems. Manufacturers must now present the products performance data in a uniform manner so that they can be directly compared and their suitability assessed for particular applications. All VADs sold for fire use in EU countries must be manufactured and certified to these requirements by 1st March 2013. For countries such as the UK which do not currently require CE marking to the CPD, compliance will be enforced from July 1 2013 when the Construction Products Directive (CPD) is replaced by the Construction Products Regulation (CPR). The FIA and LPCB have jointly published COP0001 Code of Practice for Visual Alarm Devices used for Fire Warning, which directly compliments BS EN54-23 and BS 5839-1. It provides guidance and recommendations on the planning, design, installation, commissioning and maintenance of VADs in and around buildings, other than single-family dwellings.
Coverage Volume
VADs will now be classified into three categories based on their intended application, namely ceiling mounted devices, wall mounted devices and an open class category. Each of these categories has specific targets for light distribution patterns in order to be compliant with EN54-23. Manufacturers should now ensure products are tested and assessed by an EU notified body to determine its coverage volume, based on the distance at which the required illumination of 0.4 lux or 0.4lm/m2 is met. The manufacturer must specify the coverage volume with the device; either on the product or with supporting documentation. Therefore you should always look for the coverage volume specification code. Note: The flash rate of a VAD should be between 0.5Hz and 2Hz and should emit either a red or white flash. (only red or white in EN54-23)
Different light dispersion characteristics are required according to the VADs intended mounting position. Wall mounted VADs will effective in a wide range of applications, but the manufacturer will be required to state a mounting height; which is a minimum 2.4m, followed by the width of a square room over which the VAD will provide coverage. Therefore, the specification code with a VAD suitable for a wall application could read W-2.4-6, i.e. mounted at a height of 2.4m the VAD will cover a room 6m square. The VAD will therefore be required to cover the volume below its mounting height. Any light going upwards will be wasted as far as this categorisation is concerned.
Ceiling mounted VADs are suitable for broad coverage in regular shaped rooms. Ceiling VADs must state the height of the ceiling at which it is designed to operate. This can be 3m, 6m or 9m. The VAD in this case needs to radiate light in a cylinder below the mounting point. Therefore the specification code could read C-6-6 i.e. mounted at a ceiling height of 6m, the VAD will cover a cylinder 6m in diameter.
The open class category allows for different light distribution patterns that do not fall within the restrictions of the wall or ceiling. The shape of the pattern and its coverage volume must be determined and stated by the manufacturer; however the minimum illuminance of 0.4 lm/m2 is still required.
Design
External factors can have a significant impact on the effectiveness of VADs. LPCB COP 0001 (A VAD application code of Practice developed jointly by LPCB and the FIA) advises that when designing systems incorporating VADs, it is important to consider what these influences, such as the level of ambient light, the reflectivity of surfaces, effect of colour, the required field of view and the use of tinted eye protection may have at the onset of the design.
Ambient Lighting- Because of the large variations in ambient light levels which can exist in some locations, it is important that the highest level expected should be considered when selecting VADs. Measures to control the ambient light such as blinds or curtains may help reduce its impact. A lux meter complying with BS 667 should be used to determine the ambient light levels, although it should be considered that light levels in some rooms with large window areas will vary throughout the day and from season to season.
Reflective Surfaces – It is important to assess and understand the types of surfaces involved as different materials will react differently to the emitted light. The reflection of light may be specular e.g. a glass mirror or it may be diffuse reflecting the light in many directions such as from a granular surface. Many surfaces will exhibit both types of reflections.
Field of View -Consideration should also be given to the presence of an obstruction in the field of view, such as partitions or furniture, as this could affect the VAD coverage. At any position within a space where a VAD is required, any individual should be able to view its light directly or reflected from adjacent surfaces.
Environment -The selection of VADs should also take into consideration the nature of the environment where it is intended to be installed. Type A VADs require a minimum ingress protection (IP) of IP21C, whilst type B requires a minimum IP of IP33C for more exposed locations.
When considering the siting and spacing of VADs in a room, it should be ensured that all occupants of the room have a clear line of sight of the device, but there should not be undue dependence on this in applications such as an office, where people predominantly spend their time looking at computer screens or focusing on a specific activity. Reflective surfaces can increase the field of vision by providing multiple paths for the light to attract their attention. Where the space to be covered is larger than the specified coverage volume of a device, a sufficient number of devices should be sited to ensure the required illumination levels are satisfied.
Power Consumption
To meet the requirements of BS EN54-23 and cover a practical room size encountered in most situations, VADs will be required to have higher light output levels than those generally used in the market today. Higher illuminace levels will result in a significant increase in current consumption due to the use of higher output devices or to a greater number of less powerful units. Application of the inverse square law to light radiating from a point implies that, “to double the distance from a light source will require four times the power to achieve the same level of luminosity”. LED technology can offer a breakthrough here, offering more efficient production of light, leading to lower power requirements than Xenon tube based devices. Although the initial cost of LED VADs may be slightly more expensive than Xenon products, the more efficient operation that LED’s offer means the number of devices required on an alarm circuit is reduced, consequently reducing the burden on control panel power supplies and decreasing installation costs by avoiding supplementary power supplies. This should be considered in the design of a system.
A further strain on power consumption can be the flash colour. Across most of Europe a flashing red light denotes a fire alarm signal; however red light consumes more power than white light for the same intensity. To achieve red light, white light, particularly from xenon tubes has to be filtered by a lens that allows, only the red wavelengths to pass through. This can reduce the light output by up to 80% and therefore requiring more higher output devices to achieve the require illuminance levels.
The BS EN54-23 requirements of 0.4 lm/m2 means that using red light requires a big increase in current compared to the same illumination using white light; this is exacerbated when room size is factored in. System designers are presented with a dilemma; should they offer a white flash to save power consumption and move away from the traditional red light associated with fire, or should they factor in the price of additional power supplies and installation costs, significantly increasing the total cost of the system?
The choice to use red or white VADs may not be just down to cost, the long established use of red for fire in some organisations may require a change in culture and retraining, but it should also be considered that whatever colour is chosen then it should be used consistently across the whole site, so existing beacons may have to be removed or changed.
Now the BS EN54-23 has become mandatory, it is an opportunity for the industry’s leading manufacturers to build on existing expertise and experience to develop innovative solutions to the issues of power consumption and the challenges that light output and flash colour present. This should make the transition as easy as possible for those operating in the industry, including risk assessors, installers, system designers and commissioning officers.
Written by Leanne Danby from Cooper Fulleon
Cooper Fulleon can offer help and guidance with understanding the requirements of the new standard and its implications. Contact Cooper Fulleon if you require further information on 01633 628500 or customerservice@fulleon.co.uk
