BRE Global discusses Visual alarm devices
EN 54-23:2010 is the standard to which all visual alarm devices must be approved by March 2013, and the LPCB Code of Practice (CoP 4001) provides recommendations on their effective use.
Fire alarm systems often include some form of visual element, such as a flashing light, to reinforce the audible warning from a bell, siren or voice alarm. But where building occupants include deaf or hard-of-hearing people or where there are high levels of ambient noise, the visual element must be just as effective as the audio warning in alerting people to danger.
The need for visual alarm devices (VADs) will be identified as part of a business and building’s fire risk assessment and VADs that produce sufficiently intense light to give an effective warning must be fitted. The question is, what level of performance is required to ensure that a VAD provides suitable warning?
Performance standard
Until last year there was no product standard specifying the performance requirements of VADs. This all changed with the publication of the product standard, EN 54-23: Fire alarm devices – Visual alarms in June 2010. EN 54-23 specifies VAD requirements, test methods and performance criteria. It sets a base level of product performance to give assurance that, when approved VADs are installed in accordance with the manufacturer’s instructions, they will work properly in the service environment.
As well as for buildings occupied by the deaf or hard-of-hearing, EN 54-23 compliance is a requirement for areas of high ambient noise, such as factories, where people have to wear ear defenders to comply with health and safety legislation.
Compliance by March 2013
VAD manufacturers now have until March 2013 to introduce products that comply with EN 54-23:2010. However measuring the light output from a flashing device and determining the volume that it illuminates to the specified levels requires specialist equipment. This is determined when manufacturers have their VADs tested to the standard by a notified approval body and then an appropriate category specification is declared for the device.
‘To ensure an effective fire warning for the deaf and hard of hearing, the requirements of EN 54-23 are very rigorous,’ says Raman Chagger, Senior Consultant at LPCB – the first certification body in the UK to offer a UKAS accredited service for testing and approval to the standard. ‘LPCB has been involved in writing EN 54-23 and, as well as conducting trials, has provided test methods to CEN TC72 WG3, the European Standards working group responsible for writing the Standard.
‘Our new light measurement equipment has been designed to overcome all the technical complexities of the standard,’ says Chagger. ‘It also has the flexibility to be used for product development purposes, having many additional features above and beyond the test requirements of EN 54-23.’
The bespoke piece of equipment used for conducting the majority of pulsed light measurements from EN 54-23 was supplied by Product Technology Partners (www.ptpart.co.uk), and was developed with staff at LPCB.
‘The technical challenges posed by the new standard are considerable,’ says Martin Saxon, Director of PTP. ‘Compliance would have been hard to achieve without working in partnership with LPCB. Their application experience combined with our own expertise in the innovative use of technologies enabled the development of robust yet economic test equipment that fully meets the measurement requirements.’
Among the challenges to be overcome by the test facility in measuring light intensity, were the differences between the Xenon and LED light sources (amongst others) used in VADs. The profile of an LED pulse has a comparatively long duration (typically 10-100ms) with a low peak signal and square wave type profile, while Xenon devices are of very short duration (typically <0.3ms) with a rapid high peak signal and exponential decay.
The peak signal from a high output Xenon device can be over 10,000 times greater than the peak signal generated from an LED device and this presents a difficulty in terms of the dynamic range of the measurement equipment. Additionally the standard requires measurements at a variety of different angles, up to 871 measurement positions for a ceiling mounted device with a range greater than 17m.
Code of practice
LPCB has recently produced – with the involvement of the Fire Industry Association (FIA) – a Code of Practice for Visual Alarm Devices. While EN 54-23 specifies the minimum requirements for the device performance, the Code provides recommendations for the planning, design, installation, commissioning and maintenance of VADs in and around buildings (other than single family dwellings). In short, the Code of Practice provides guidance on the use of EN 54-23 compliant VADs, for example how they should be spaced in a building.
The Code of Practice for Visual Alarm Devices will soon be available on the RedBookLive website www.redbooklive.com
For more information please contact: fdetenquiries@bre.co.uk
Raman Chagger is Senior Consultant in BRE Global’s Fire Detection and Electronics Testing team
Directory listing:
BRE Global
© Copyright 2011 Means Of Escape Terms & Conditions Privacy Policy
Copyright © 2011 Think Agency - Website Designers Kent