Benefits of a voice alarm system

Benefits of a Voice Alarm System

Voice Alarm System (VAS) / Voice Evacuation systems have become increasingly popular for providing clear pre-recorded emergency messages. Installed with the safety of staff and general public as a key function, our systems assist in the effective evacuation of an area or building during a fire, bomb alert or other emergency. At all other times a voice alarm system may be used for full-cover or zoned public address announcements, broadcast advertisements or background music.

Traditional bells and sounders only give warning tones, they do not indicate the nature of the emergency, leaving people uncertain and such signals, if ignored, may result in fatal consequences. The VAS helps to ensure that even untrained personnel and the general public are evacuated speedily and efficiently.

Voice Alarm System (VAS) / Voice Evacuation systems  can install in all offices, factories, warehouses, shops, sports arenas, cinemas, theatres, schools and public buildings. Combined with our expertise in all aspects of Fire and Life Safety and our ability to provide bespoke integrated systems – including monitoring and intelligent building systems – we ensure all messages are broadcast clearly and all emergency procedures and systems operate efficiently and effectively to ensure safety.

Controlled evacuation

In high rise buildings with large occupancies, a combination of clear pre-recorded messages and live announcements broadcasted to selected zones enable a controlled and gradual process of evacuation (referred to as phased evacuation). Phased evacuation methods enable selected areas to be evacuated in turn; typically those in most danger will be evacuated first, while surrounding zones are put on alert. The VAS works automatically, with all controls easily overridden by fire officers or building control when needed.

In many buildings it is not possible to use a lift in the event of a fire; lifts are often made to travel to the ground floor the instant the fire alarm system is activated. This leaves the stairwells and other evacuation routes available for people to follow in order to escape the building. In a high rise, or any multi-level building, simply expecting everyone to leave the building at the same time could, potentially, lead to panic and blockage on these evacuation routes. The ability to initiate a controlled, area-by-area evacuation of a building – phased evacuation – helps prevent this.

Staged evacuation is the process where staff or occupants may be alerted to a situation that is being investigated, while the responsible staff ascertain the danger before evacuating the building or cancelling the event. Such a process is best supported using a clear, pervasive and quick method of communication. It may be incredibly difficult to cancel an evacuation in progress without clearly understood instructions and organisations may experience significant business continuity losses in the event of false alarms.

Some manufacturers of professional voice alarm systems and electro-acoustic emergency warning systems are currently working on loop technology for 100 V loudspeaker connections. Usually, loudspeakers are still connected to the voice alarm system through spur technology. If a spur circuit is interrupted, however, all loudspeakers after the wire breakage would fail. During a short circuit, the entire spur circuit fails. In order to minimize risk in the case of wire breakage and short circuit, A/B cabling is used for systems based on DIN VDE 0833-4 (security levels 2 and 3), with half of the loudspeakers in a room operating on different loudspeaker lines. Thus, in a wire-to-wire short circuit (wire breakage, short circuit or ground fault), half of the loudspeakers in the relevant area remain in operation. So if the alarms sound at half power, the sound level is reduced by 3 dB, as long as the loudspeakers are correctly arranged. This level decrease is permitted in accordance with DIN VDE 0833-4 standards. In contrast to fire detection technology, loop wiring technology itself has not yet been established as the standard in the area of voice alarm systems (VAS), because considerably higher power must be transmitted there.

International evacuation standards

The following is an extract from SANS10139. If you are doing phased or staged evacuation on the fire system, then the voice evacuation system will follow the same principles

“There are various circumstances in which a staged fire alarm arrangement may be appropriate. These include, but are not restricted to, the following:

a) In certain large or high-rise buildings, it might be desirable to evacuate first those areas closest to the fire and immediately above it; other areas are evacuated thereafter. A particular example of this arrangement, commonly used in high rise buildings, is known as phased evacuation; in this case, conventionally, the floor of fire origin, the floor immediately above (and, often, any below ground areas) are evacuated as a first phase. Thereafter, each subsequent phase involves evacuation of two floors at a time, until all floors are evacuated in a number of such phases. This arrangement enables the number and/or widths of stairways to be reduced; under these circumstances, it is important that no control is provided to evacuate the entire building in a single phase, as there will be insufficient stairway capacity for simultaneous evacuation of all occupants.

b) Phased evacuation is also sometimes used in other types of building, irrespective of whether there are reduced stairway capacities (e.g. leisure complexes, shopping centres and transportation terminals). In these cases, the initial phase of evacuation may be horizontal, into a place of relative safety within the building.

c) In hospitals, a system of ‘progressive horizontal evacuation’ is used, in which patients closest to a fire are moved horizontally to an adjacent fire compartment. In a large hospital, further evacuation might, again, involve only horizontal movement, without the need for more difficult vertical evacuation.”

Despite all of the evidence reporting the greatly increased response times and improved evacuation, installations of VAS are still relatively low. For general applications in larger projects such as arenas, shopping malls and high-rise buildings, VAS installations are steadily increasing; for smaller buildings it is still fairly uncommon.

A VAS has to work when needed (especially and specifically during an emergency) and is, therefore, fully monitored at all times. Furthermore, the system is backed up by batteries which are fully charged and checked constantly; this will ensure that during a mains power failure, the system will continue to operate. Each voice alarm system is designed and built specifically for each project; typically, no two systems are identical.

A standard system built using today’s state-of-the-art technology in accordance with DIN VDE 0833-4 or EN 60849, an A/B or simple cabling in spur technology is sufficient, depending on the application. Though loop technology requires additional isolator modules, they initially create additional costs. However, at second glance the entire system can be significantly less expensive, with cost savings in other places. So, depending on the application, cost-intensive E30 cabling can be partially avoided.

In regard to building ordinances, DIN VDE 0833-4 is not specified for required voice alarm systems in section 7.10.3. This may be waived for loop wiring systems of otherwise functional integrity, if it is guaranteed that forward and return lines are routed in separate cables, and that these cables are laid out separately in buildings with fire protection technology. In addition, it must be ensured that the intended function of the VAS is not affected by a single failure in these loop wiring systems. That might be the case in the technology described here.

It is a sad state of affairs that our current building regulations in South Africa do not specifically request the requirement for voice evacuation systems, leaving the door open to omit these systems as a cost saving exercise, overlooking the safety benefit of these systems and putting the lives of people who occupy the buildings in jeopardy.

Benefits of a VAS

• Clear, spoken instructions to people during an emergency event.

• Selectable pre-recorded messages.

• Microphone priority handling.

• Full control during the evacuation of a building/phased evacuation: area-by-area, floor-by-floor, multiple areas/ floors all at once – whichever is most appropriate for the situation and layout of the building.

• Supports dynamic issuing of instructions and routing of persons away from danger through clear communication.

• Battery-backed: the system will continue to operate even in the event of a mains power failure.

• Ability to cancel false alarms and announce all clear messages.

• Ambient noise sensing: broadcasts will still be heard regardless if the background noise levels increase (the VA system can automatically adjust the volume of the broadcast).

• Day-to-day advantages: public information announcements, background music (gain revenue via advertisement injection and more).