A quick guide to the BS 5839-1:2025 changes concerning cables

BS 5839-1:2025 Fire Detection and Fire Alarm Systems for buildings - Part 1: Design, installation, commissioning, and maintenance of systems in non-domestic premises - Code of practice is essential reading for designers, installers, commissioners and maintainers of fire detection and fire alarm systems in buildings mainly used for commercial, public, or industrial purposes such as hotels, shops and restaurants.

The focus of the standard is system design; it does not dictate whether a commercial premises requires a fire detection and fire alarm system - that is determined by legislation such as Building Regulations. Its purpose is to provide comprehensive recommendations and guidance on planning, design, installation, commissioning and maintenance of fire detection and fire alarm systems. This British Standard does not apply to domestic premises, that is detailed in Part 6 which is due for review soon.

It is also important to note that while the standard is a code of practice and takes the form of recommendations, Clause 6 sets out which of these recommendations it is "considered unacceptable" not to adopt. 

While the technical requirements in the latest version remain largely consistent, the content of the 2025 revision has been refined and reorganised to provide greater clarity, more structured guidance and updated references.

Key changes in the 2025 revision include:

• Updated terms and definitions to bring them in line with the newly published fire vocabulary standard, BS 4422:2024
• The siting recommendations for manual call points have been simplified 
• Stairway lobbies are now covered with automatic detection
• Improved guidance on fire detection in sleeping areas
• Clarification of the period between service visits to acknowledge that it is not always possible to carry out routine maintenance of a fire detection and fire alarm system on exactly the same day every year.

The sections have also been renumbered, for example Section 26: Cables wiring and other interconnections, is now Section 25

What about the cable?

Section 25: Cables, wiring and other interconnections (formerly Section 26) has retained the core principle of maintaining circuit integrity during a fire. This requires that all cables must ensure interconnections between elements of both fire detection system and fire alarm systems and that they must operate for an appropriate length of time.

The level of a cable's fire resistance is referred to as "standard" and "enhanced", terms originally introduced back in the 2002 version of BS 5839-1. These requirements have remained the same in the 2025 revision. 

Prysmian Fire Performance (FP) cables fully satisfy the requirements of the latest revision. For a cable to be classed as standard fire resistant, it has to meet the PH30 classification when tested in accordance with BS EN 50200 but also BS EN 50200 Annex E (which includes the water spray test which has to be carried out simultaneously). This means it is proven to continue to operate for a minimum of 30 minutes. Prysmian FP200 Gold is an excellent "standard" fire resistant cable and is fully compliant to be used with BS 5839-1.

Enhanced fire resisting cable should meet the PH120 classification with a proven operational time of 120 minutes when tested in accordance with both BS EN 50200 and also BS 8434-2. This makes it suitable for use in large or complex buildings where cables must withstand higher temperatures and more demanding conditions to ensure safety is not compromised. Prysmian FP PLUS is suitable for use in applications where cables with "enhanced" fire resistant cables are required. 

Other points to note in the latest revision is that the requirement for fire resisting cables to have a minimum conductor cross-sectional area of 1mm² remains unchanged. The standard also makes clear that black or white cables should not be used for fire detection and fire alarm systems; the preferred colour is red to ensure easy identification. 

A word of caution to those responsible for system maintenance: while there is nothing in the new revision that requires older systems to be brought in line with the new standard, it is necessary to maintain and service an existing system to the new standard.

As a leading cable manufacturer, Prysmian was part of the British Cables Association team providing support to the Technical Committee.

For more information on Prysmian FP cables click here.