Voice Evacuation - BS5839 Part 8 Explained

Our Voice Evacuation Systems have been designed and is built to meet the relevant British standards. One of these is BS5839: ‘Fire detection and alarm systems for buildings’.

This has been revised to include Part 8: The code of practice for the design, installation and servicing of voice alarm systems.

There are some disciplines hidden within BS5839 Part 8, which we would like to point out to you. These include:

1. At least two loudspeaker circuits are required in the building. If the building contains an open area greater than 4,000m² or if the building is designed to accommodate more than 500 members of the public, dual circuits should be used. This achieves suitable coverage should one of the circuits become short or open circuit.

2. Cabling for dual circuits must not be contained in one single sheath.

3. Where a processor-controlled system is used the following points must be followed:

• Any system configuration data should have restricted access.
• Do not use rotary discs (i.e. computer hard disc) or any other media moving parts.
• Any processor must be monitored e.g. ‘watchdog’.
• Should the processor fail and re-gain normal operation there should be a processor reset indication on the equipment and a fault announced.
• At least one emergency microphone must have the provision to manually access an All Call, should the processor fail.

4. The monitoring of the system should include the following:

• Normal power.
• Standby power.
• Battery chargers.
• Fuses & protective devices.
• Critical signal paths. See definition ~ number 8.
• Emergency messages.
• Loudspeaker circuits.
• Standby amplifiers.
• Select wires on a multi-zone emergency microphone.
• All links between a de-centralised system.
• Detection of missing modules or amplifiers within the critical signal path.
• Automatic level controllers must be monitored and should fail safe to a pre-determined level, not mute.

5. The system should latch the input condition from the fire panel ensuring that if a link is broken the alarm broadcast continues. Reset is achieved by a separate signal from the fire panel.

6. After reset the system should be capable of producing a general evacuate broadcast within 30 seconds.

7. Any fault should be indicated or announced within 100 seconds.

8. A reserve amplifier should be used to provide backup to maintain the required speech intelligibility in the event of amplifier failure.

9. Definition of critical signal paths ~ all components and interconnections between every fire alarm broadcast initiation point and the input terminals on, or within each loudspeaker enclosure.