Fire-rated smoke extract ductwork forms one part of a coordinated smoke-control system. Its construction and installation must suit the system duty, required fire classification, duct route, pressure conditions and supporting test or assessment evidence.
EN1366.co.uk provides practical guidance for consultants, contractors and clients. This page explains how specialist ductwork manufacture, insulation and installation should be coordinated with an approved fire strategy, smoke-control design and tested or assessed ductwork system.
This guidance does not replace the project fire engineer, smoke-control designer or consultant. The fire strategy, system operating sequence, fan duty, damper operation and cause-and-effect requirements must be established by the responsible project designers.
Fire-rated ductwork is a complete system
Fire-rated ductwork is not simply sheet metal manufactured from a non-combustible material. It is a complete tested or assessed construction. Depending on the selected system, the evidence may cover the duct material and gauge, stiffening, flanges, joints, fasteners, sealants, gaskets, access doors, supports, anchors, penetrations, fire stopping, insulation or protection and the installation method.
Changing one component can affect the evidence supporting the complete construction. A substitute product should not be assumed acceptable merely because it is non-combustible or separately described as fire rated.
Which fire-rated ductwork standard applies?
The likely standards route depends on the function and route of the ductwork. It must be confirmed against the fire strategy, smoke-control design, project specification and applicable system evidence.
| Application | Likely standards route | Practical meaning |
|---|---|---|
| Fire-resisting ventilation ductwork | BS EN 1366-1 / BS EN 13501-3 | Ventilation ductwork intended to resist fire spread between compartments. Evidence must cover the required construction, orientation and exposure conditions. |
| Multi-compartment smoke extract ductwork | BS EN 1366-8 / BS EN 13501-4 | Smoke extract ductwork that passes through a fire compartment other than the compartment from which smoke is extracted. |
| Single-compartment smoke extract ductwork | BS EN 1366-9 / BS EN 13501-4 | Smoke extract ductwork serving a single compartment and not passing through another fire compartment. |
| Smoke-control duct sections | BS EN 12101-7 | The product standard for smoke-control duct sections intended for smoke and heat control systems. |
| Older UK fire-resistance route | BS 476 Part 24 | A legacy route still encountered in existing specifications and assessment evidence. Its acceptability must be checked for the project and current regulatory context. |
| General duct construction and leakage | BESA DW/144 and DW/143 | General sheet-metal duct construction and leakage-testing guidance. Compliance with these documents alone does not make ductwork fire resisting. |
This is a simplified guide rather than a substitute for the standards. Classification details, pressure limits, dimensions, orientations and permitted variations must be checked against the relevant classification report, field of application, assessment and manufacturer documentation.
How does a smoke-extract system typically operate?
In a typical zoned system, the fire detection or alarm system identifies the affected floor, compartment or smoke-control zone. Subject to the approved design, the smoke-control system may then open the relevant smoke-control damper or ventilator, confirm the required device positions, start the duty fan and operate any required replacement-air or pressure-control provisions.
Other dampers are normally kept closed unless the fire strategy requires a different response. This can help preserve compartmentation, concentrate extract duty on the affected zone, reduce the risk of drawing smoke into unaffected areas and allow the fan and pressure controls to operate at their intended duty.
This is not a universal operating rule. The actual sequence must be established by the fire strategy, smoke-control designer and approved cause-and-effect matrix.
Who determines the operating sequence?
- Fire strategy author or fire engineer: establishes the fire-safety and life-safety objectives.
- Smoke-control designer or specialist: develops the proposed smoke-management method and system response.
- Mechanical or building-services consultant: coordinates ductwork, fans, dampers, replacement air and pressure control.
- Calculations or CFD: may be required to assess or demonstrate the intended performance.
- Cause-and-effect matrix: records the required response of each component under the defined fire scenarios.
- Commissioning team: tests and records whether the completed system operates as intended.
Ductwork manufacture and installation must support the approved design, but the ductwork contractor should not independently determine the building’s smoke-control strategy.
Information required before pricing or manufacture
The following information should be supplied where applicable:
- Current fire strategy and smoke-control design report.
- Approved cause-and-effect matrix and CFD report or calculations, where applicable.
- Coordinated drawings, duct routes and system or zone descriptions.
- Required standards route: EN 1366-1, EN 1366-8, EN 1366-9 or an accepted BS 476 Part 24 route.
- Required classification and duration, including E, I and S criteria where applicable.
- Pressure, leakage, horizontal or vertical orientation and fire-exposure requirements.
- Fan duty, maximum system pressure and replacement-air provisions.
- Damper schedule, classification, type and proposed installation position.
- Duct dimensions, fittings, access requirements and space restrictions.
- Wall and floor constructions, penetration details and fire-stopping system.
- Hanger, support, anchor, insulation and fire-protection requirements.
- The proprietary, protected or bare-metal tested system specified or accepted for the project.
- Site leakage testing, inspection, photographic records and hold points.
- Required conformity statement, O&M and handover wording.
Where information is unavailable or contradictory, it should be raised before the pricing basis or manufacturing scope is finalised.
From specification to manufacture and installation
Subject to the agreed design, project requirements and applicable system evidence, specialist ductwork support may include:
- Reviewing the ductwork scope against the specified fire-rated system.
- Highlighting missing or conflicting information before manufacture.
- Reviewing whether proposed sizes, routes and orientations appear to fall within the stated system evidence.
- Manufacturing fire-rated ductwork to the agreed tested or assessed construction.
- Supplying or coordinating the specified fire-rated insulation or protection.
- Installing ductwork, supports and protection where included within the order.
- Coordinating ductwork interfaces with approved dampers and access requirements.
- Supporting inspection records, O&M manuals and project handover information.
- Providing a project-specific conformity statement for the defined fabricated and/or installed works, where agreed.
Any project review should be limited to the ductwork scope and information supplied. Final system design and acceptance remain with the project’s competent designers and approving parties.
Whole-system performance depends on more than ductwork
Smoke-control performance also depends on the fire strategy, smoke-control calculations, fan selection, dampers, fire-alarm interfaces, controls, power supplies, replacement air, commissioning and acceptance by the relevant project stakeholders. Correct ductwork cannot compensate for an incomplete or unsuitable system design.
What should a ductwork conformity statement cover?
Where included within the contractual scope, a specialist ductwork contractor may provide a project-specific statement covering the ductwork it fabricated and/or installed. The document may confirm that the defined works were completed in accordance with the approved-for-construction drawings, agreed tested or assessed arrangement, applicable manufacturer requirements and relevant project specification.
The document title, defined scope, exclusions and required wording should be agreed before manufacture or installation begins. Any statement should relate only to the work and responsibilities expressly identified within it.
It does not replace independent fire-test or classification reports, field-of-application documents, system-owner assessments, product certification, fire-strategy approval, smoke-control calculations, fan or damper certification, cause-and-effect verification, whole-system commissioning or acceptance by an approving authority.
Common fire-rated ductwork mistakes
- Treating A1 or non-combustible ductwork as automatically fire rated. Material reaction to fire does not demonstrate the performance of the assembled duct system.
- Assuming ordinary DW/144 ductwork is fire resisting. A fire-resisting system requires applicable test, classification or assessment evidence.
- Mixing components from different tested systems. Duct construction, joints, sealants, supports, access doors and protection should not be substituted without appropriate evidence.
- Changing metal material or gauge without checking. A seemingly stronger alternative should not automatically be assumed acceptable.
- Omitting fire-rated supports or penetration details. Supports, anchors, wall or floor construction, fire stopping and clearances form part of the coordinated arrangement.
- Using unsuitable connectors, gaskets or access doors. Every incorporated item must suit the required performance and evidence.
- Assuming all dampers open together. Damper operation must follow the approved zone strategy and cause-and-effect matrix.
- Leaving leakage requirements until completion. The test pressure, method and acceptance criteria should be defined before tender.
- Closing inaccessible work too early. Joints, supports, penetrations and protection may require inspection before being concealed.
Send us your project information
Send your ductwork drawings, specification and fire-rating requirements for an initial scope review. This can help identify missing information and establish a suitable pricing basis for manufacture, insulation and installation, subject to confirmation by the responsible project designers.
Commercial manufacture and installation enquiries submitted through EN1366.co.uk are handled by DuctFix.
Important guidance note
The information on this page is general guidance for fire-rated ductwork coordination only. Smoke-control system design must be undertaken by competent designers using the project fire strategy, current standards, manufacturer evidence, calculations or CFD where required and an approved cause-and-effect matrix.
This guidance does not replace the role of the fire engineer, smoke-control designer, approving authority or project consultant. Project requirements and system suitability must be confirmed using the applicable design information and supporting evidence.
Source basis: BS EN 1366-1, BS EN 1366-8, BS EN 1366-9, BS EN 13501-3, BS EN 13501-4, BS EN 12101-7, BS 476 Part 24 and BESA DW/143 and DW/144. This page is an original practical summary and does not reproduce or replace those documents.
Guidance review: September 2026. This is an original practical summary and does not reproduce or replace the relevant standards or project evidence. How this guidance is reviewed.