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2026-02-26 17:43:12 R. Bishop: Initial Commit
/dev/null .. fire alarms/regulations/bs 5839/zones.md
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+ # 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)
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