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BS 5839 and Its Application to Fire Alarm Systems

Understanding BS 5839

BS 5839 is the British Standard that sets out best practice recommendations for the design, installation, commissioning, and maintenance of fire detection and alarm systems. It plays a vital role in achieving compliance with UK fire safety legislation, particularly in non-domestic buildings such as offices, schools, healthcare facilities, and commercial premises.

BS 5839 is split into two major parts:

  • BS 5839-1 → Applies to fire detection and alarm systems in non-domestic premises.
  • BS 5839-6 → Covers systems used in domestic (residential) premises.

This page focuses on the updated BS 5839-1:2025 edition, which replaces the 2017 version.

Why BS 5839-1:2025 is Essential for Fire Alarm Systems

Compliance with BS 5839-1:2025 helps to:

  • Improve life safety by enabling early warning and effective evacuation.
  • Reduce property damage through prompt detection and fire brigade response.
  • Satisfy legal obligations under fire safety laws like the Regulatory Reform (Fire Safety) Order 2005.
  • Provide a structured approach to system reliability, false alarm reduction, and robust documentation.

While it is not a legal document in itself, BS 5839-1 is widely used to demonstrate compliance with statutory fire safety duties.

Key Changes Introduced in the 2025 Edition

Clause Restructuring and New Section

  • Clause 4 has been moved into the Introduction.
  • Clause 33 on false alarms is now integrated with Clause 31.
  • A new Section 7 has been added, covering extensions and modifications to existing systems.

Stricter Variation Controls

  • Certain departures from recommendations are now clearly stated as unacceptable in Clause 6. For example, omitting a zone plan in multi-zone buildings is not permitted.

Improved Manual Call Point Guidance

  • Siting rules have been simplified. Manual call points must be no more than 45m travel distance, or 30m if the layout is uncertain.

Detector Use in Sleeping Accommodation

  • The standard now advises against using heat detectors in sleeping rooms, recommending faster-reacting alternatives instead.

Cybersecurity Considerations

  • Clause 43.4 includes requirements for cybersecurity and remote services, acknowledging modern system vulnerabilities.

Key Elements of BS 5839-1:2025 for Fire Alarm Systems

System Categories and Purpose

  • Category M → Manual systems without automatic detection.
  • Category L → Life protection (L1 to L5, based on risk).
  • Category P → Property protection (P1 or P2).

Each category outlines specific detection coverage and design principles.

System Design Considerations

  • Risk-Based Design → System layout must be informed by a fire risk assessment.
  • Detector Selection → Match detector types to environmental risks (e.g. avoid heat in sleeping areas).
  • Alarm Performance → Sound pressure levels must be sufficient for clear occupant warning.
  • False Alarm Strategy → Use appropriate siting, configuration, and detection technologies to reduce nuisance activations.

Installation Requirements

  • Cabling → Must be fire-resistant and installed using appropriate support systems.
  • Power Supply → Both mains and compliant standby battery supply must be verified.
  • Call Point and Detector Positioning → Follow updated distance limits and placement rules.

Inspection and Maintenance

  • Weekly Testing → Test a manual call point each week.
  • Monthly Checks → Inspect batteries and verify charging systems.
  • Annual Servicing → Comprehensive testing of all components.
  • Logbook Maintenance → Record tests, faults, false alarms, and maintenance actions.

Consequences of Non-Compliance

Failure to comply with BS 5839-1:2025 can result in:

  • Increased safety risk due to ineffective alarm coverage.
  • Legal action under fire safety legislation.
  • Frequent false alarms, risking fines or loss of confidence in system performance.
  • Insurance issues, including potential refusal of claims after a fire.

Final Thoughts

BS 5839-1:2025 reflects modern best practices and addresses lessons learned from fire incidents. Compliance supports:

✅ Safer buildings and occupants. ✅ Fewer false alarms. ✅ Legal and insurance alignment.

Whether you're designing, installing, or maintaining a fire alarm system, applying the updated BS 5839-1 is essential to uphold safety, legal duties, and system performance.