[
Visual alarms should supplement audible fire alarms in places such as sleeping accomodation, according to the Disability Discrimination Act which was fully inplemented in October 2004. But, asks Vivian Jones of Vimpex, is the fire alarm industry in its search for low current systems, just paying lip service to the legislation?
Firstly, without apology, I want again to go on record about my belief that there should be a common fire alarm tone. I first raised this issue six years ago when the Fire Cryer voice enhanced sounder was introduced.The Fire Cryer was created in order to combat the potential confusion on hearing an alarm and not understanding what it signified – in other words a sounder than can be both heard and understood.
For centuries, the humble but distinctive fire bell has served the public well. Most people, on hearing the bell, would know what it signified, although some confusion could result when two stage alarms were used. In this case, the bell would sound for approximately one second on, one second off, indicating an alert intended to put you on standby for a possible evacuation of the building. A continuous tone meant you should leave the building and move to your assembly point.
A little over 25 years ago, we saw the growth of electronic alarm sounders – these were introduced primarily as they offered lower current consumption and less electrical interference. As electronic sounders gathered popularity, more and more manufacturers entered the market, each time introducing their own specific tone!
There are at least 32 different tones in use in Europe. Even in markets where it is believed a specific tone or tones are specified by national standards, you will still find sounders being installed which do not comply. What chance the public have of knowing what to do? So one can understand why the use of voice sounders is gathering pace, albeit greatly hampered by the demand of the market for lower current devices! More on this point later.
Now what has all this to do with the Disability Discrimination Act? It is my view that the fire industry should learn from the history of the past 25 years and think about what it is truly attempting to achieve when raising the alarm.
During this period, we have seen a great deal of investment by fire detector manufacturers seeking improvements in detection and a reduction of false alarms. The introduction of ‘intelligent’ analogue addressable systems promised improvements and undoubtedly there have been many. Unfortunately, false alarms remain with us and still threaten to undermine the public’s confidence in the systems.
The introduction of addressable circuits, allowing both detectors and sounders to be powered on the same loop, obviously ensures lower installation costs. There is a down side, however, and that is the insatiable demand of the manufacturers for devices with lower and lower current consumption. The result is there for all to hear! Well of course not everyone can, so back to the DDA.
We now have the responsibility to ensure that disabled persons are not discriminated against, and this includes the alarms we supply to provide a fire warning and possible need for evacuation. We are not concerned only about profoundly deaf or totally blind people, or indeed the blind deaf – we must also be conscious of those only partially affected. So we are now required to provide visual alarms to supplement the audible alarms.
Visual alarms in the guise of Xenon beacons have been used for many years. Often they are specified where either a silent alarm is required or, more usually, where there is a high noise level, such as in a factory environment. They generally have a significantly higher current consumption than bells, sounders or voice enhanced sounders. However, quite recently we have seen the introduction of new LED technology that offers visual alarms with lower current consumption. There are other benefits – such as longer life and easier synchronisation – but it is the lower current consumption (a common thread) which is the main benefit. In fact, just like the demand for low current sounders compromising sound and frequency levels, we are now in danger of a similar story unfolding with visual alarms! How many should there be, how bright should they be, and what colour?
If we look further a field outside our domestic and even European markets, we find the USA introduced the Americans with Disabilities Act (ADA) – which was enacted in July 1990 – and the industry there is now engaged in developing systems to meet what they call ‘Mass Notification Systems’. Basically, how best to get the public, including those covered by the DDA, out of a building quickly and safely.
Surely we could gain by seriously investigating this approach. While there is no lessening of the commitment to automatic alarms, there is also a parallel commitment to good, safe and effective evacuation. Notwithstanding the differences in buildings, people and legislative influences between the US and UK, the objectives of evacuation are surely common.
We see in the US a tremendous growth in the use of strobes, and these in some cases are up to a 100 times brighter than some of those used in the UK. Of course, the current is high and generally the strobe has a clear lens, which provides upwards of double the light output when compared with a red or amber lens, but of course with no additional current. Although it is common to install sounders with integral strobe throughout a building, it is likely that more strobes than audible devices may be required, as light – unlike sound – will not penetrate doors or travel around corners.
In the UK, a typical 24 volt strobe is quoted as having a 2 watt output. In essence, this is a meaningless value and at best might describe it as brighter than a 1 watt and less than a 5 watt!
There is much debate as to how to measure strobe light outputs and I do not propose to go into the detail here. But whereas the 2 watt strobe referred to is likely to be in the order of 0.8 candela/sec (with clear lens), the typical ADA product will be in the order of 75-175 candela, albeit not at all viewing/ sight angles.
If we were to adopt or closely follow the US ADA standards, much higher outputs will be required. US research has shown that to be effective, a visual signal must be able to raise the overall light level sharply – 90% of research subjects were alerted by a 75 candela strobe mounted 50 feet away on a wall directly behind them. For this reason, a minimum performance criterion of 75 candelas using white light has been recommended. Coloured lamps (particularly red) were not effective, even at extreme intensities.
Furthermore, the flash rate should be between 1Hz and 3Hz – rates exceeding 5Hz may be disturbing to persons with photosensitivity. This would require either careful positioning of strobes to avoid a cumulative effect of strobe flash rates, or synchronisation of the strobes.
The debate over the measurement of strobe outputs rated by candelas, candela/sec, watts, Joules or lumens, may well will intensify. But there is no doubt that to achieve even 75 candela requires considerably more current than is available on most addressable loops.
There is little doubt that the UK fire industry – mainly due to the influence of the DDA – will see the growing use of visual alarms. While we can envisage future developments improving LED technology, it will be a long time before they will be bright enough at acceptable currents for addressable systems.
There are opportunities for our industry, as well as difficulties facing us, as we deliberate over the best approach to ensure everyone is alerted to a fire alarm. In my view, however, the difficulty is simply recognising that we may need to move forward beyond the demand for low current devices, and look more to devices that do the task intended!
It could well be that we see the separation of alarm sounder/strobe circuits from addressable loops, so they are connected in their own dedicated circuit. Freeing up the restraints on current will allow manufacturers to create voice sounders that can not only be heard and understood, but seen too! In essence our Industry must do more than pay lip service to the DDA.