Visual alarm devices Application Guide
- Where to use VADs
- What is EN54-23?
- Design Considerations
- Ambient Light
- Field of view
- Reflactive surfaces
- Zettler VADs
- Ceiling Mounted
- Wall Mounted
- Using VADs in spaces with obstacles
- Power Supplies and Wiring
European standard EN54-23 Where to use Visual Alarm Devices (VADs)
Over recent years, the installation of Visual Alarm Devices (VADs) has experienced considerable growth since their mandatory introduction from 1st January 2014. This is in response to both the Equalities Act 2010 (UK only) and historical data which clearly demonstrates the effectiveness and reliability of VADs.
VADs are required to be used, in specific circumstances,in conjunction with other alarm devices to provide an effective means of alerting and evacuating occupants of a building. It is essential that the use of VADs forms part of the overall fire safety strategy. This strategy is based on an agreed building evacuation plan which, in turn, is a product of the buildings fire risk assessment. Initially, before commencing any system design, it’s advisable to carry out a Fire Risk Assessment of the area to determine if VADs are required. If there is no requirement then, in addition to EN54-3 compliant sounders, Visual Indicating Devices (VIDs) would be a supplementary requirement to raise an event awareness.
Although EN54-23 has no definitive guidance with regards to how a risk assessment is carried out, the outcome of such an assesment may impact possible alarm solutions. For a more in-depth understanding of fire risk assessment please review the training section at www.fia.uk.com. Local building Regulations Part M, BS5839-1, Loss Prevention Code of Practice - CoP0001, BS9999 and BS8300 recommend that VADs should be installed in places where audible devices alone would be ineffective, or where they are simply undesirable.
Applications where VADs would be installed:
- As a Visual warning for persons with impaired hearing (deaf or hard of hearing).
- Areas or places where people are likely to be on their own. - Where hearing protection is being worn or areas where ambient noise exceeds 85dba
- (factories, production, workshops, machine rooms etc.). Please note: In industrial and manufacturing areas it is essential to ensure that the visual Fire Alarms are clearly distinguishable from any other visual signals used for machine or process alarms.
- Bedrooms/sleeping areas in accommodation such as hotels, student accommodation, HMOs.
Please note: These devices are not intended to wake sleeping people. In these circumstances more effective methods should be considered, such as vibrating devices.
- Broadcasting studios of Television, Radio and recording.
- Nursing Homes. - Hospitals (operating theatres) for which guidance is given in HTM 05-03 Part B.
- Toilet facilities, including all types and not limited to accessible/assisted areas.
- Fire Alarm systems using Gaseous Extinguishing systems – indication of first stage alarm (see BS 7273-1). - To avoid unnecessary disruption from false alarms.
- Cinemas and Theatres Building where phased fire evacuation strategy is employed such as shopping malls, high rise or large buildings, hospitals.
- Public assembly buildings and entertainment complexes. Here staff only warning systems could utilise VADs as an initial alarm prior to a full evacuate signal.
For the purposes of this document we have used the terms and definitions given in EN54-23 and BS5839-1 along with the Royal National Institute for Deaf people (RNID) and the Royal Association for Deaf people (RAD) are as follows:
Hard of hearing person
A person who can only hear above 25dBA but can hear sounds less than 80Dba.
A person who cannot hear sounds less than 80 Dba.
Ambient light level
The ambient light level typically present in an area of a building, which is likely to vary over the course of a day, is taken into consideration when designing a VAD installation.
A VAD combined with another fire detection device and fire alarm system. For example, Combined VAD and alarm sounder, or VAD and smoke detector.
Recurrent convulsions precipitated by visual stimuli, particularly flickering light seizures are most likely to be triggered by frequencies between 3 Hz and 30 Hz, although this varies from person to person it is unlikely that seizures.
What is EN54-23?:
The European Committee for Standardization, CEN released EN54-23, a new mandatory standard from 1st January 2014. Prior to its release, no EN standard existed for visual alarm devices. Therefore, misinterpretation and confusion over a product’s performance was a common concern in the industry.
Outputs can be stated in many different units of measurement, i.e Joules, Candela or Watts. EN54-23 provides clarity, standardizes the requirements, test methods and performance criteria of VADs and ensures light output is now measured in a uniform manner throughout Europe.
Main requirements from EN54-23 are:
The coverage volume (i.e. volume within which required illumination is achieved) must be stated on the product or in supporting documentation.
VAD shall meet the requirement for coverage volume of at least one of the following categories: W (Wall), C (Ceiling), O (Open Class).
Required illumination of 0.4 lux on a surface perpendicular to the direction of the light emitted from the VAD.
The rate of flash should be stated between 0.5Hz and 2Hz.
The devices are classified as Type A for indoor purposes, and Type B, for outdoor applications.
Access to the device shall be restricted by the use of special screws or tools.
It should not be possible to change the manufaturer's settings without use of the same screws/tools, or by breaking a seal. Adjustments may be carried out either at the device or via the control indicator equipment.
When designing a fire detection and alarm system, and where VADs are required, the following should be considered:
- Ambient light level.
- Field of view.
- Reflective surfaces.
- Use of tinted eye protection.
- The environment - indoor Type A devices – IP21C, outdoor Type B devices – IP33C.
- Applications where there is continuous surveillance of a VAD in a specific direction may not require widespread coverage. For, example, A seated auditorium or a broadcast studio may only require limited coverage.
- Where possible, locate the VADs for direct viewing for all occupants in an area.
- If this is not possible, consider the minimum illumination on adjacent reflected surfaces If relying on indirect illumination, the reflecting surfaces should be within the coverage area of the VAD.
- Where a coverage area is larger than that of a single VAD, an appropriate number of extra VADs should be installed.
- Dependence on direct line of sight should not be relied upon if the VAD is used where deaf or hard-of- hearing people may be alone for prolonged periods. This particularly applies to hotel bedrooms and bathrooms. It also relates to people wearing ear defenders, or where they may be working alone or focusing on a specific activity.
- In the case of stairwells, the illumination from a VAD should satisfy the recommendations across the area of each landing. Compliance may not be necessary throughout the entire stairway.
Ambient Light Level
The ambient light level in the vicinity of a VAD will affect its visibility and, therefore its ability to provide effective warning. In designing the installation, consideration should be given to the variation of the ambient light level during the periods when the VADs are intended to be effective in giving a warning of fire.
The extent of artificial lighting in combination with any natural lighting will affect the ambient light level. This level can also be influenced by external natural light conditions such as bright sunshine, daylight, overcast sky, twilight and moonlight, and may be reduced by measures such as blinds or curtains on windows.
Information on the recommended illumination in workplaces and typical ambient light levels is given in Table 1 below. However, this is for guidance only and it is important that ambient light levels are measured correctly for each application.
Always consider the highest possible ambient light level which may exist for each specific application.
In general, the coverage volume of VADs may be increased in low ambient light levels but may need to be decreased for brightly lit spaces or in spaces that can be flooded by strong daylight, such as rooms with south-facing windows.
Using vads in spaces with obstacles
Consideration should be given at the design stage to obstacles that affect the warning given by VADs by creating blind ‘spots’ with little or no direct or indirect illumination. These spaces can require a change to the number and position of VADs.
In rooms with obstacles which affect the illumination from VADs, one or both of the following should be applied:
- Sufficient numbers of VADs are installed so that any persons within the space between obstacles have a direct view of at least one VAD.
- The VADs installed provide sufficient illumination of the obstacle surfaces to ensure adequate warning to occupants who do not have direct view of at least one VAD.
In rooms where suspended items such as supply pipes and ducts (e.g. ventilation ducts) mask VADs from occupants, one or both of the following should be applied:
- Sufficient numbers of VADs are installed so that occupied areas of the room are adequately illuminated, and/or
- The VADs installed provide adequate illumination of surfaces that are adjacent to occupants of the room where those occupants do not have a direct view of at least one VAD.
Power supplies and wiring
Power supplies should conform to EN54-4 and should be compliant with the recommendation of the local installation standards and code of practices. Both the normal and standby supply should be independently capable of supplying the maximum alarm load imposed by the system and the high peak-power requirements of any VADs connected to a system should have no detrimental effect on the mandatory functions of the fire detection and alarm system.
Since VADs form part of the primary means for giving warning of fire, in particular circumstances it is essential that circuits on which they are connected operate correctly at the time of a fire. Therefore, cables with an inherent ability to resist flame & heat need to be used and compliance with BS 5839:1 sub-clause 26.2 is mandatory.
FireClass provides FireClass Designer software that allows the designer of the fire detection and alarm system to calculate the load, power requirements of individual loops in standby and alarm modes based on the devices connected and parameters such as loop length, resistance, devices types etc. This tool shall be used to validate the design of any FireClass fire detection and alarm system, including those where VADs are used.equipment.
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