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The first recorded use of voice alarms was here in England during World War II. Speakers were used in addition to the regular sirens to transmit warnings about attacks on airports, harbours and streets.

More recently, a boom in voice-alarm technology followed the blaze at Bradford City football stadium in 1985, which led to 56 deaths, and the fire at London’s King’s Cross underground station in 1987, which resulted in 31 fatalities. The two fires led to the creation of IEC 60849, Sound systems for emergency purposes, back in 1989. The standard includes intelligibility requirements for voice-alarm systems.

Independent research has shown that, in the event of an emergency, people can react without confusion or panic if they receive clear, concise and easily understood messages. Bells and sounders only give a warning, and the cause for alarm is never really clear.

Often, the very fact that there is an alarm sounding can set off fear and uncertainty in the public, with people waiting for further evidence of the danger before evacuating.

An Equinox TV programme shown in the 1980s illustrated clearly the results of extensive research work carried out by Brian Piggott at the Fire Research Centre. Presented in a paper by David Canter at Surrey University, the study showed that only 13% of people reacted to a bell sound, whereas a staggering 75% of those monitored responded to a voice issuing evacuation instructions.

Other research showed people’s behaviour varied tremendously and was often dependent on factors such as environment and even gender.

However, it also showed that, for the majority of the time, people behaved sensibly, provided they were given adequate information. Giving clear details of the present danger motivates people to move to safety.

Another discovery was that people tended to leave buildings by the same entrance they had used to enter it. This showed the need for them to be directed to the nearest escape route.

Many firms believe that, to provide a voice message in the event of an emergency like a fire, they can simply use their PA system. Unfortunately, PA, while very good for providing music and general messages, is not guaranteed to work when there is an emergency.

The study showed only 13% reacted to a bell sound whereas a staggering 75% responded to a voice

This is where the British Standard BS 5839-8:1998, Code of practice for voice alarms, comes into play. It specifies a highly secure public address system with a number of required features.

First, all internal and external circuits have to be monitored and must be supported with a minimum of 30 minutes’ battery back-up. There must also be a monitored secure link to the fire alarm panel, where a number of pre-recorded emergency messages should be stored, incorporated with an emergency fireman’s microphone.

Speech sounders are not considered valid for use in a true voice alarm system. These are more commonly used in a smaller property where a ‘one out, all out’ evacuation strategy is employed.

As you would expect, there is no substitute for reading the standard itself, and the above are only the most obvious requirements that face the designer when putting together a system. Copies of this standard can be obtained from BSI on www.bsonline.bsi-global.com.

Alongside the scope, references and definitions contained within this standard, the key section for the designer to consider is a requirement to exchange information with all interested parties.

So it is essential to understand what messages need to be played in the event of a fire or another emergency, as well as what the system may be asked to do on a daily basis, such as delivering background music and paging facilities. It provides a full planning schedule as a checklist, which is well worth following.

As you would expect, it recommends surveying the site, and this should include an acoustic assessment to ensure that the siting of voice alarms provides adequate coverage to all areas of the building. It is also important to assess general usage of the building, including periods of non-occupation, areas with high noise levels and numbers of personnel that are likely to be hard of hearing.

At present, the responsibility lies with facilities managers and building owners to decide for themselves whether a voice alarm system is best for their particular environment.

It may not be long, however, before unambiguous voice-based warning messages are integrated into fire detection or bomb-alert systems as a matter of course. Pre-recorded spoken messages aid controlled evacuation, ensuring even untrained personnel can be evacuated quickly and efficiently.