Fire Detection For All
EN54-23, the European standard on visual alarm devices, came into force on 31 December 2013. Here, Peter Lackey, Fire Product Marketing Manager at ADT Fire & Security offers advice on how to ensure a system addresses the needs of the hard of hearing.
There are an estimated 10 million people with some form of hearing impairment living in the UK and around a further two million people with a level of sight loss. It is imperative that all occupants of a building receive the same opportunity to be alerted to a fire and evacuated quickly and a new standard on visual alarm devices (VADs) will play a part in making sure that happens.
The need to establish a fire strategy that is fit for all occupants of a building is enshrined under the Equality Act 2010, the successor to the Disability Discrimination Act 1995. The Act states that evacuation notifications must exist for the hearing impaired. This is reinforced by the current Building Regulations, which demand that newly erected or substantially reconstructed non-domestic buildings provide suitable aids for the hearing impaired.
Of course, VADs are not only used as a means of giving warning to deaf and hard of hearing people. They are also used in buildings where there are areas of high ambient noise levels, or in certain public assembly buildings where the initial warning of fire may be restricted to staff. Another example would be broadcasting studios, where an audible alarm would cause interruption to live broadcasts, or hospital operating theatres where an audible alarm may be disruptive.
BS 5839-1:2013 provides recommendations for the design, installation, commissioning and maintenance of fire detection and fire alarm systems for buildings. It contains guidance on VADs, including the number and distribution of VADs, which should be readily visible from all normally accessible locations, throughout the area in which they are provided, under normal ambient lighting levels. It also covers the rate at which VADs should flash; the height at which VADs should be mounted; the differentiation of the visual signal from any other visual signal used in the premises and the intensity of output, which should be sufficient to attract attention, but not so high as to cause difficulty with vision due to glare.
BS 5839-1:2013 recommends that VADs comply with EN54-23. While VADs have been on the market for a number of years, EN54-23, the pan-European standard on VADs which came into force on 31 December 2013, imposes tougher standards in terms of the light output of devices. This has resulted in manufacturers developing new equipment ranges.
EN 54-23 specifies the requirements, test methods and performance criteria for VADs in fire detection and fire alarm systems. The performance of VADs is assessed against a minimum required illumination of 0.4 lux (0.4 lumens per square metre) on surfaces perpendicular to the direction of the light emitted from the device. The measured light intensity of the device is used to define the effective space (coverage volume) that it can cover. This minimum level is such that adequate visual warning will be given on any surfaces within the coverage volume, so that the device does not necessarily have to be directly within the field of view of the recipient to be effective. The flash rate must be between 0.5 and 2.0Hz.
VADs are classifieds in three categories: ceiling-mounted, wall-mounted and open class. Each of these categories is further defined by the geometry of the coverage volume, (open class being specified by the manufacturer). The coverage volume can thus be used to determine VAD spacing within the building.
For ceiling-mounted devices, the standard defines the maximum height at which it can be installed, set by the standard 3, 6, or 9 m. A wall-mounted device must be installed at a minimum of 2.4m from the floor. The coverage volume, is that in which the output meets the minimum illumination requirement of 0.4 lux on a perpendicular surface.
The standard also calls for careful consideration of the colour of light emitted. Although both red and white light can still be specified, EN54-23 highlights that red LEDs can result in a loss of 80% of the light output, meaning red VADs are not energy efficient and drastically reduce the coverage area compared to white light.
Generally, white flashing light is more effective in alerting individuals as it includes a broader spectrum of colours and care should be taken when using red flashing light since it is more likely to induce a seizure in susceptible individuals.
User responsibilities for VADs should be in accordance with the recommendations of Clause 47 of BS 5839-1:2013. In particular, the person responsible for the system should ensure the following:
• General fire notices include an explanation of the audible and visual warning system in the event of a fire
• All deaf and hard of hearing people are aware of the actions required in the event of a VAD activation
• If a VAD is used for a staff alarm, people are adequately trained in the required actions
• If there are any changes to the layout or utilisation of a room or space that could result in reduced VAD effectiveness then the VAD installation design is reviewed
• Since all visual alarm signals produced by VADs within a building should have similar characteristics, all additional or replacement VADs are compatible with those already present.
Anyone specifying VADs to help protect those with a hearing impairment, as part of a robust and fit-for-all fire safety strategy, needs to be aware that as of 31 December 2013, existing products on the market have been replaced with EN 54-23 compliant products. ADT offers a range of conventional VADs that can be installed as part of an EN54-23 visual alarm system including both wall and ceiling category devices. Furthermore, we can provide specifiers with guidance and support to ensure fire detection and alarm systems are compliant and offer the highest levels of fire safety.
Published August 2014