Electrical
Fire alarm and detection design
Fire detection and alarm system design to BS 5839-1:2025, with the system category agreed against the fire strategy.
- Discipline
- Electrical
WHAT IT IS
Fire detection and alarm design determines what is detected, where, how the alarm is raised, and what the system does to other building systems when it operates.
The starting point is the system category from BS 5839-1 — L1 to L5 for life protection, P1 and P2 for property protection, M for manual only. The category is a decision that belongs with the fire strategy and the responsible person, not a default the services engineer picks; the design then delivers it.
WHEN YOU NEED IT
On new build, on change of use, on any alteration that changes the compartmentation or escape strategy, and where a fire risk assessment has identified that the existing system category is not adequate for the use.
DELIVERABLES
What you receive
- System category recommendation against the fire strategy
- Detection and alarm device layouts
- Cause and effect matrix
- Zone plan
- Interface schedule for plant shutdown, door release and lift homing
STANDARDS
Standards applied
The editions in force at the time of design. Where a standard is amended mid-project we confirm which edition the appointment is based on.
- BS 5839-1:2025Fire detection and fire alarm systems for buildings — code of practice for design, installation, commissioning and maintenanceBSI
- BS 5839-6:2019+A1:2020Fire detection and fire alarm systems in domestic premisesBSI
- Approved Document BFire safety (England)GOV.UK
- Technical Handbook Section 2Fire (Scotland)Scottish Government
- BS 8644-1:2022Digital management of fire safety informationBSI
QUESTIONS
Common questions
What are the fire alarm categories in BS 5839-1?
BS 5839-1:2025 defines Category M for manual systems, Categories L1 to L5 for automatic systems intended to protect life, and Categories P1 and P2 for systems intended to protect property. L1 covers the whole building; L5 is a bespoke category designed to satisfy a specific fire safety objective.
Who decides the fire alarm category for a building?
The category is determined by the fire strategy and agreed with the responsible person under the Regulatory Reform (Fire Safety) Order 2005, or the duty holder under the Fire (Scotland) Act 2005. The services engineer designs the system to deliver the agreed category rather than selecting it in isolation.