Voice Alarm and PA/VA Systems
When a tone sounder goes off, people often hesitate — is it a test, a fault, a real fire? A clear spoken instruction removes that doubt, and that is the core value of a voice alarm system. This guide covers the basics of voice alarm (PA/VA) systems: what they are, why intelligible speech improves evacuation, where they suit, and how they connect to the fire detection system.
Voice alarm is a specialist area with its own standard, but every fire alarm engineer benefits from understanding the principles.
Who this is for
This is for competent fire alarm engineers who want a grounding in voice alarm systems before working alongside or interfacing with one. The experience level assumed is competent engineer. Use it for the concepts; use the current standards and the manufacturer's documentation for design, commissioning and intelligibility criteria.
What a voice alarm system is
A voice alarm — often called PA/VA, for public address and voice alarm — delivers intelligible spoken evacuation messages through loudspeakers, and usually supports live announcements too. It is driven by the fire detection and alarm system so that pre-recorded messages play automatically in the correct areas according to the cause and effect. Voice alarm systems in the UK are designed and installed to BS 5839-8, the code of practice for voice alarm, working alongside BS 5839-1 for the detection system.
Why speech improves response
Research and experience both show that clear spoken instructions get people moving faster and more correctly than a tone alone. A message can tell occupants exactly what is happening and what to do, which is especially valuable where the population is unfamiliar with the building or where a phased or staged evacuation is used. That improvement in occupant response is the reason voice alarm is specified in larger and more complex buildings.
Intelligibility
A voice message only helps if people can understand it. Intelligibility — how clearly speech can be made out over background noise and through the building's acoustics — is therefore central to voice alarm design and commissioning. It is measured and verified, not assumed. Highly reverberant or noisy spaces are challenging, and getting adequate intelligibility there is a large part of the design effort. Poor intelligibility defeats the purpose of the system.
Interfacing with detection
The fire detection system provides the trigger and the cause and effect: which detectors and zones initiate which messages in which areas. The voice alarm system delivers those messages. The interface between the two must be correct and must be tested together, so that the right message reaches the right area at the right time. From field experience, interface and cause-and-effect errors — the wrong message in the wrong zone — are exactly what thorough commissioning and testing exist to catch.
Common points to check
Recurring issues include areas with marginal intelligibility, message-to-zone mapping errors, and changes to a building's layout or use that affect coverage and acoustics. Where you interface with a voice alarm system, verify the cause and effect and confirm the messages behave as intended.
When not to rely on this alone
When not to use this article: do not use it to design a voice alarm system, set intelligibility targets, or configure messages. Those come from the current BS 5839-8, the manufacturer's documentation and competent design, applied to the specific building and evacuation strategy.
Relevant standards
Voice alarm systems are designed and installed to BS 5839-8, a code of practice, alongside BS 5839-1 for the detection system. The legal duty to warn occupants effectively in most non-domestic premises derives from the Regulatory Reform (Fire Safety) Order 2005. Separate the legal duty from the recommended methods when advising a client, and always work to the current editions and the manufacturer's data.
Professional disclaimer
This is an educational resource for competent engineers and does not replace the current British Standards, the manufacturer's documentation, the site fire strategy, or competent design judgement. Verify all voice alarm design and commissioning against current documentation.
Related documentation
Use this with the current BS 5839-8 and BS 5839-1, the voice alarm manufacturer's documentation, and the system design and cause and effect. Record intelligibility results and message mapping in the commissioning documentation.