# Zoning Requirements under BS 5839-1:2025 ## Overview Under **BS 5839-1:2025**, zoning is a fundamental design principle of fire detection and fire alarm systems. Proper zoning ensures that: * The location of a fire can be quickly identified * Occupants can evacuate safely * Fire & Rescue Service attendance is effective * The fire strategy of the building is supported Zoning is covered primarily in: * **Clause 12 - Fire Detection Zones** * **Clause 13 - Alarm Zones** Zoning must always align with the evacuation strategy and system category (L or P category). --- # 1. Fire Detection Zones (Clause 12) ## Definition A **fire detection zone** is: > A subdivision of the protected premises such that the occurrence of a fire within it is indicated separately from an indication in any other subdivision In simple terms: * Each zone must allow responders to narrow down the fire location. * A fire signal must identify *which* part of the building is in alarm. --- ## 1.1 General Requirements All fire detection zones must: * Be clearly identifiable at the Control & Indicating Equipment (CIE) * Correspond with a **Zone Plan** * Be arranged to assist in locating the fire quickly * Support safe evacuation and firefighting operations --- ## 1.2 Maximum Zone Size Under BS 5839-1: * A fire detection zone should not normally exceed **2,000 m²** * A single zone should not normally extend beyond: * More than one storey * Separate fire compartments (with some defined exceptions) ### Storey Rule Each storey should normally be treated as: * A separate fire detection zone Exceptions may apply where: * The total floor area is small * The building layout makes multi-storey zoning logical --- ## 1.3 Search Distance Requirement The standard introduces the concept of **search distance**: > The distance a person must travel within a zone to determine the fire’s location Search distance should not normally exceed: * **60 metres** This ensures: * Firefighters can rapidly identify the seat of fire * Zones are not so large that location becomes impractical --- ## 1.4 Zoning in Non-Addressable Systems For conventional (non-addressable) systems: * Each zone corresponds to a physical circuit * Automatic detectors and MCPs are grouped per zone * The panel indicates only the zone, not the device Therefore: * Zone design is critical to minimise search time * Larger buildings require more zones --- ## 1.5 Zoning in Addressable Systems In addressable systems: * Each detector has a unique address * Exact device location is displayed However: ⚠ **Zoning is still required** Even with full addressability: * The building must still be subdivided into fire detection zones * Zones must still comply with maximum area and search distance rules * A zone plan is still required Addressability does not remove zoning obligations. --- ## 1.6 Manual Call Point (MCP) Only Zones Where a zone contains only MCPs: * It may exceed 2,000 m² in certain circumstances * However, clarity of indication must still be maintained --- # 2. Alarm Zones (Clause 13) ## Definition An **alarm zone** is: > A geographical subdivision of premises in which a fire alarm warning can be given separately and independently from other subdivisions This relates to: * Sounder circuits * Phased evacuation * Staged alarm systems --- ## 2.1 Relationship to Evacuation Strategy Alarm zones must align with: * Simultaneous evacuation strategy * Phased evacuation strategy * Staff alarm strategies * Two-stage alarm systems For example: | Evacuation Type | Zoning Implication | | ----------------------- | ----------------------------- | | Simultaneous evacuation | Often single alarm zone | | Phased evacuation | Multiple alarm zones required | | High-rise buildings | Floor-by-floor alarm zoning | --- ## 2.2 Independence of Alarm Zones Where multiple alarm zones are used: * A fault in one zone must not disable others * Sounder circuits may need duplication in large open areas * Zoning must prevent total loss of warning in critical spaces --- # 3. Zone Plans (Clause 22.2.5) BS 5839-1:2025 makes it clear that: A **Zone Plan** must be provided where: * There is more than one zone on any storey The plan must: * Be displayed adjacent to the CIE * Clearly show: * Building layout * Zone boundaries * Zone numbers * Staircases * Final exits ### Unacceptable Variation Clause 6 explicitly states that: > The absence of a zone plan in premises with more than one zone per storey - particularly premises in which people sleep - is unacceptable This is considered a serious life safety deficiency. --- # 4. Zoning and System Categories Zoning design must reflect system category: | Category | Zoning Expectation | | -------- | --------------------------------------------------------- | | L1 | Full building coverage - zoning per storey or compartment | | L2 | Zoning includes high-risk rooms + escape routes | | L3 | Escape routes + rooms opening onto them | | L4 | Circulation spaces only | | L5 | Custom zoning to meet specific objective | | P1 | Full property coverage | | P2 | Defined high-risk property areas | Improper zoning can undermine: * The life safety objective * Fire engineering solutions * Compartmentation strategies --- # 5. Common Design Mistakes ### ❌ Over-Large Zones Exceeding 2,000 m² or 60 m search distance. ### ❌ Multi-Storey Zones Without justification. ### ❌ No Zone Plan A serious non-compliance. ### ❌ Confusing Fire Detection Zones with Alarm Zones They serve different purposes. ### ❌ Assuming Addressable Systems Remove Zoning Requirements They do not. --- # 6. Engineering Considerations (UK Practice) In real-world UK installations: * High-rise residential blocks typically zone per floor. * Schools often zone per wing or floor. * Hospitals require zoning aligned with progressive horizontal evacuation. * Warehouses may require additional subdivision despite open plan. Zoning should always be: * Risk-based * Strategy-driven * Documented in design certificate * Reflected in cause & effect programming --- # 7. Zoning is a Design-Stage Responsibility Fire detection zoning must be determined **during the system design stage**, not during installation or commissioning. Under BS 5839-1:2025: * System category must be defined before design begins (Clause 4) * Responsibilities for design must be clearly documented (Clause 5) * Variations must be formally recorded and justified (Clause 6) * A formal **Design Certificate** is required (Annex G) Because zoning affects: * Compliance with maximum zone size * Search distance * Storey separation * Cause & effect programming * Alarm zoning * Zone plan layout * Fire strategy alignment …it forms part of the **core system design**. --- ## Design Certificate Implications The Design Certificate confirms that: * The system category has been correctly selected * The protected areas are defined * Zoning complies with BS 5839-1 * Any variations are declared If zoning is not defined at design stage: * The designer cannot legitimately sign the Design Certificate * Responsibility becomes blurred * Compliance is questionable * Liability increases --- ## Practical Engineering Note (UK Reality) On many UK projects: * Zoning is “worked out on site” * Zone boundaries are adjusted after first fix * The zone plan is drawn after commissioning This approach is non-compliant. The **zone layout should be agreed and documented before installation begins**. Installation should follow the design, not determine it. --- ## Best Practice At design stage, the designer should produce: * A zoning drawing * Defined zone numbers * Zone boundaries per storey * Confirmation of zone sizes (m²) * Confirmation of search distances * Alarm zoning strategy * Statement of compliance within the Design Certificate --- # 8. Compliance Checklist When reviewing a design: * [ ] Does each zone comply with 2,000 m² limit? * [ ] Is search distance ≤ 60 m? * [ ] Is each storey separately zoned? * [ ] Is a zone plan provided? * [ ] Do alarm zones align with evacuation strategy? * [ ] Are fault scenarios considered? --- # References * BS 5839-1:2025 - Clause 12 (Fire detection zones) * BS 5839-1:2025 - Clause 13 (Alarm zones) * BS 5839-1:2025 - Clause 22.2.5 (Zone plans) * BS 5839-1:2025 - Clause 6 (Unacceptable variations)