The almost automatic response of many fire system designers when addressing the need for visual alarms is simply to complement sounders with flashing beacons. Often, however, this is an unsatisfactory or incomplete solution, says Don Scott, fire engineering consultant with Siemens Building Technologies Fire Safety.

The Disability Discrimination Act (DDA) makes service providers and employers responsible for ensuring that people with disabilities do not receive less favourable treatment than their able-bodied counterparts. In practical terms, this means that fire alarm systems have to emit both audible and visual warnings when a fire is detected, to cater for the needs of those with visual and hearing impairments.

The technology for providing audible warnings is well established, but when it comes to visual warnings the situation is much less clear-cut. The usual approach is to supplement the audible warning devices with flashing beacons, but this is not nearly as straightforward an option as it may at first appear.
 

A beacon is used to alert occupants of a disabled toilet

Consider, for example, the type of beacon that will be used. Most popular with designers are loop-powered beacons, which derive their power from the loop cabling that is used to link detectors in modern fire alarm installations. The big benefit of using beacons of this type is that no additional wiring is required.

But there’s a problem. The loop can only supply a limited amount of power. In practice this means that, in all but the smallest of installations, beacons with LED light sources have to be used, and these emit light of only moderate intensity. Certainly, they will attract the attention of someone who happens to be looking in the right direction but, particularly in a brightly lit room, it is very possible that they will go unnoticed by those who are not looking directly at them.

Seeing red?
In the UK, this situation is made even worse by an insistence on using red flashing beacons. Research has shown that red is the least effective colour for attracting attention; white light is much more effective. It is also worth noting that a red filter can significantly reduce the intensity of light emitted by the light source, making low-intensity sources even less noticeable.

However, when clear lenses are used, all of the light can get through. In the USA they use only white lenses, and fire strobes are mounted in red containers to denote that they are fire.

In rooms such as hotel bedrooms, where people may be sleeping, low-intensity flashing beacons are a particularly poor choice. To rouse someone from sleep requires a beacon with an intensity of between 75 and 110 candelas, which is well above the intensity achieved by typical loop-powered LED beacons.

Clearly, a LED beacon is not going to wake someone who is asleep. In fact, alternative technologies such as vibrating pillows have been shown to have a better effect. Such alternatives tend to have their limitations, however. Suppose, for example, the person occupying the room prefers to sleep without a pillow. It may be necessary, therefore, to use a combination of technologies to achieve the desired results.

But why not simply use high-intensity beacons with xenon light sources? Actually, these bring their own problems. First of all, they require more power than can be conveniently provided from the detector loop, so they need separate power wiring. This makes installation more complicated and increases costs. In addition, xenon tubes are less reliable than LED light sources, so the performance of the beacons must be checked regularly.

Lateral thinking
Both types of beacon and many of the possible alternatives clearly have shortcomings, so what’s to be done? The answer is to apply a little lateral thinking to the specific case in hand. Hotel bedrooms are, for example, invariably equipped with reasonably bright room lights. Why not arrange for the alarm system to flash the room lights in the event of a fire? This is far more likely to attract attention and rouse sleepers than the flashing of a low-intensity LED beacon.

Of course, it may not be instantly clear to the room occupant why the lights are flashing, but this issue can be addressed by making use of something else that is now present in almost every hotel room – the television. Turn the televisions on in all of the rooms, and use them to display an alert message along with evacuation instructions.

There are other possibilities. It has, for example, been seriously proposed that the visual warning device could be replaced by a device that instead of light emits the smell of wasabi, a pungent form of horseradish widely used in Japanese cuisine. Tests, which not surprisingly were carried out in Japan, showed that this smell woke sleepers within two minutes. Except, of course, for those who had colds!

In reality, it’s not likely that olfactory warning devices will ever become common in the UK, but this anecdote does indicate that there is a very wide range of options beyond beacons!

Beacons are, of course, not only used in fire protection systems to help meet the requirements of the DDA; they are also a popular choice for applications where high noise levels might mean that an audible alarm would go unheard. In these situations, high-intensity xenon beacons may be the right solution, despite their relatively high cost of installation.

Ambient noise
Nevertheless, consideration should also be given to alternatives. Would vibrating pagers, for example, be a better solution? In a noisy workshop where arc welding is being carried out producing bright flashes of light that might mask the flashes from a beacon, pagers could well be an attractive option.

In this short article, it has only been possible to discuss a few of the issues that surround the use of beacons as warning devices in fire detection systems. Hopefully, however, enough has been said to show that beacons should not always be an automatic choice. There are undoubtedly applications where beacons of the correct type are the best option, but there are many others where a different approach could provide a better and often less costly solution.

Don Scott is fire engineering consultant with Siemens Building Technologies Fire Safety