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99eb3d R. Bishop 2026-02-26 17:43:12 1 
# Zoning Requirements under BS 5839-1:2025
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## Overview
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Under **BS 5839-1:2025**, zoning is a fundamental design principle of fire detection and fire alarm systems. Proper zoning ensures that:
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* The location of a fire can be quickly identified
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* Occupants can evacuate safely
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* Fire & Rescue Service attendance is effective
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* The fire strategy of the building is supported
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Zoning is covered primarily in:
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* **Clause 12 - Fire Detection Zones**
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* **Clause 13 - Alarm Zones**
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Zoning must always align with the evacuation strategy and system category (L or P category).
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---
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# 1. Fire Detection Zones (Clause 12)
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## Definition
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A **fire detection zone** is:
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> 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
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In simple terms:
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* Each zone must allow responders to narrow down the fire location.
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* A fire signal must identify *which* part of the building is in alarm.
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---
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## 1.1 General Requirements
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All fire detection zones must:
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* Be clearly identifiable at the Control & Indicating Equipment (CIE)
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* Correspond with a **Zone Plan**
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* Be arranged to assist in locating the fire quickly
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* Support safe evacuation and firefighting operations
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---
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## 1.2 Maximum Zone Size
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Under BS 5839-1:
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* A fire detection zone should not normally exceed **2,000 m²**
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* A single zone should not normally extend beyond:
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* More than one storey
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* Separate fire compartments (with some defined exceptions)
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### Storey Rule
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Each storey should normally be treated as:
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* A separate fire detection zone
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Exceptions may apply where:
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* The total floor area is small
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* The building layout makes multi-storey zoning logical
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---
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## 1.3 Search Distance Requirement
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The standard introduces the concept of **search distance**:
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> The distance a person must travel within a zone to determine the fire’s location
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Search distance should not normally exceed:
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* **60 metres**
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This ensures:
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* Firefighters can rapidly identify the seat of fire
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* Zones are not so large that location becomes impractical
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---
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## 1.4 Zoning in Non-Addressable Systems
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For conventional (non-addressable) systems:
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* Each zone corresponds to a physical circuit
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* Automatic detectors and MCPs are grouped per zone
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* The panel indicates only the zone, not the device
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Therefore:
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* Zone design is critical to minimise search time
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* Larger buildings require more zones
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---
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## 1.5 Zoning in Addressable Systems
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In addressable systems:
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* Each detector has a unique address
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* Exact device location is displayed
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However:
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⚠ **Zoning is still required**
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Even with full addressability:
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* The building must still be subdivided into fire detection zones
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* Zones must still comply with maximum area and search distance rules
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* A zone plan is still required
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Addressability does not remove zoning obligations.
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---
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## 1.6 Manual Call Point (MCP) Only Zones
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Where a zone contains only MCPs:
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* It may exceed 2,000 m² in certain circumstances
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* However, clarity of indication must still be maintained
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---
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# 2. Alarm Zones (Clause 13)
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## Definition
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An **alarm zone** is:
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> A geographical subdivision of premises in which a fire alarm warning can be given separately and independently from other subdivisions
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This relates to:
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* Sounder circuits
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* Phased evacuation
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* Staged alarm systems
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---
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## 2.1 Relationship to Evacuation Strategy
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Alarm zones must align with:
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* Simultaneous evacuation strategy
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* Phased evacuation strategy
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* Staff alarm strategies
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* Two-stage alarm systems
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For example:
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| Evacuation Type | Zoning Implication |
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| ----------------------- | ----------------------------- |
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| Simultaneous evacuation | Often single alarm zone |
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| Phased evacuation | Multiple alarm zones required |
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| High-rise buildings | Floor-by-floor alarm zoning |
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---
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## 2.2 Independence of Alarm Zones
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Where multiple alarm zones are used:
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* A fault in one zone must not disable others
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* Sounder circuits may need duplication in large open areas
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* Zoning must prevent total loss of warning in critical spaces
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---
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# 3. Zone Plans (Clause 22.2.5)
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BS 5839-1:2025 makes it clear that:
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A **Zone Plan** must be provided where:
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* There is more than one zone on any storey
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The plan must:
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* Be displayed adjacent to the CIE
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* Clearly show:
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* Building layout
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* Zone boundaries
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* Zone numbers
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* Staircases
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* Final exits
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### Unacceptable Variation
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Clause 6 explicitly states that:
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> The absence of a zone plan in premises with more than one zone per storey - particularly premises in which people sleep - is unacceptable
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This is considered a serious life safety deficiency.
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---
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# 4. Zoning and System Categories
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Zoning design must reflect system category:
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| Category | Zoning Expectation |
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| -------- | --------------------------------------------------------- |
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| L1 | Full building coverage - zoning per storey or compartment |
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| L2 | Zoning includes high-risk rooms + escape routes |
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| L3 | Escape routes + rooms opening onto them |
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| L4 | Circulation spaces only |
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| L5 | Custom zoning to meet specific objective |
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| P1 | Full property coverage |
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| P2 | Defined high-risk property areas |
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Improper zoning can undermine:
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* The life safety objective
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* Fire engineering solutions
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* Compartmentation strategies
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---
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# 5. Common Design Mistakes
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### ❌ Over-Large Zones
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Exceeding 2,000 m² or 60 m search distance.
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### ❌ Multi-Storey Zones
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Without justification.
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### ❌ No Zone Plan
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A serious non-compliance.
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### ❌ Confusing Fire Detection Zones with Alarm Zones
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They serve different purposes.
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### ❌ Assuming Addressable Systems Remove Zoning Requirements
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They do not.
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---
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# 6. Engineering Considerations (UK Practice)
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In real-world UK installations:
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* High-rise residential blocks typically zone per floor.
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* Schools often zone per wing or floor.
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* Hospitals require zoning aligned with progressive horizontal evacuation.
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* Warehouses may require additional subdivision despite open plan.
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Zoning should always be:
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* Risk-based
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* Strategy-driven
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* Documented in design certificate
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* Reflected in cause & effect programming
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---
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# 7. Zoning is a Design-Stage Responsibility
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Fire detection zoning must be determined **during the system design stage**, not during installation or commissioning.
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Under BS 5839-1:2025:
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* System category must be defined before design begins (Clause 4)
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* Responsibilities for design must be clearly documented (Clause 5)
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* Variations must be formally recorded and justified (Clause 6)
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* A formal **Design Certificate** is required (Annex G)
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Because zoning affects:
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* Compliance with maximum zone size
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* Search distance
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* Storey separation
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* Cause & effect programming
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* Alarm zoning
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* Zone plan layout
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* Fire strategy alignment
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…it forms part of the **core system design**.
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---
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## Design Certificate Implications
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The Design Certificate confirms that:
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* The system category has been correctly selected
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* The protected areas are defined
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* Zoning complies with BS 5839-1
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* Any variations are declared
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If zoning is not defined at design stage:
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* The designer cannot legitimately sign the Design Certificate
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* Responsibility becomes blurred
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* Compliance is questionable
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* Liability increases
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## Practical Engineering Note (UK Reality)
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On many UK projects:
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* Zoning is “worked out on site”
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* Zone boundaries are adjusted after first fix
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* The zone plan is drawn after commissioning
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This approach is non-compliant.
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The **zone layout should be agreed and documented before installation begins**.
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Installation should follow the design, not determine it.
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## Best Practice
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At design stage, the designer should produce:
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* A zoning drawing
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* Defined zone numbers
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* Zone boundaries per storey
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* Confirmation of zone sizes (m²)
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* Confirmation of search distances
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* Alarm zoning strategy
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* Statement of compliance within the Design Certificate
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# 8. Compliance Checklist
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When reviewing a design:
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* [ ] Does each zone comply with 2,000 m² limit?
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* [ ] Is search distance ≤ 60 m?
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* [ ] Is each storey separately zoned?
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* [ ] Is a zone plan provided?
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* [ ] Do alarm zones align with evacuation strategy?
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* [ ] Are fault scenarios considered?
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# References
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* BS 5839-1:2025 - Clause 12 (Fire detection zones)
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* BS 5839-1:2025 - Clause 13 (Alarm zones)
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* BS 5839-1:2025 - Clause 22.2.5 (Zone plans)
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* BS 5839-1:2025 - Clause 6 (Unacceptable variations)