What does BS EN 12101-7 cover?

BS EN 12101-7 specifies requirements for smoke ducts: ducts designed to carry smoke and hot gases from smoke extract fans. It covers construction, materials, testing, and classification of ducts intended to remain intact during a fire for the duration needed to maintain smoke extraction.

Why do smoke extract ducts need to be classified?

If a smoke extract duct passes through compartments other than the fire compartment, it must be constructed to prevent fire and smoke spreading to unaffected areas. An unclassified duct that fails during a fire could allow smoke to travel to floors above or adjacent zones, undermining the evacuation strategy.

What temperature and duration classifications apply to smoke ducts?

BS EN 12101-7 classified ducts are designated with the operating temperature (matching the fan: typically 300°C) and duration (e.g., 120 minutes). Ducts within the fire compartment only are typically unclassified standard metalwork; ducts passing through compartments or adjacent floors require classification.

Is a smoke duct the same as a fire-rated duct?

No. A fire-rated duct (used for supply air or general extract) is designed to resist the passage of fire and smoke from outside into the duct. A smoke duct is designed to carry smoke from inside, and it must maintain structural integrity at high temperature while actively conveying smoke. The performance criteria and test methods are different.

BS EN 12101-7: Smoke Duct Compliance Guide

BS EN 12101-7 specifies the requirements for ducts used specifically in smoke ventilation systems - the ductwork that conveys smoke from extract grilles or damper positions to the point of discharge outside the building. Unlike standard HVAC ductwork, smoke ducts must maintain structural integrity and smoke-tightness under the elevated temperatures and pressures present during a fire event.

Part of the BS EN 12101 standard family.

Why Smoke Ducts Are Different

Standard ventilation ductwork is designed for ambient temperature operation. During a fire, smoke extract ductwork must:

Withstand hot gas temperatures of 200°C or higher for extended periods
Maintain a gas-tight seal so extracted smoke cannot leak into adjacent spaces
Retain structural integrity under the mechanical stresses imposed by fire conditions
Not contribute to fire spread through their fabric or insulation

BS EN 12101-7 establishes the test methods and performance classifications that allow smoke ducts to be selected and specified with confidence.

Key Requirements

Temperature and Duration Classification

Ducts are classified by the temperature they must withstand and the duration, using the same format as other BS EN 12101 components:

Classification	Temperature	Duration
F200/30	200°C	30 min
F200/60	200°C	60 min
F200/120	200°C	120 min
F300/60	300°C	60 min
F600/30	600°C	30 min

For most UK residential and commercial buildings, F200/60 is the standard specification. High-rise or complex buildings may require F200/120.

Leakage Classification

Duct leakage is classified at test pressure conditions relevant to the system operating pressure. Tighter leakage classifications ensure extracted smoke cannot bypass the ductwork and enter occupied zones.

Structural Integrity

Ducts must not collapse, buckle, or open at joints under the combined effects of heat, negative pressure (extraction), and their own weight. Support spacings are specified to maintain alignment and prevent sagging.

Penetrations and Fire Stopping

Where smoke ducts pass through fire-rated walls or floors, the penetration must be appropriately fire-stopped. Any dampers installed in the duct must meet BS EN 12101-8 requirements.

Specification Checklist

When specifying smoke ducts under BS EN 12101-7, confirm:

Temperature classification - e.g. F200/60
Leakage class - tested leakage rate at system pressure
Duct cross-section - rectangular or circular, in mm
Material - steel gauge, insulation type and thickness
Support centres - maximum spacing between hangers
Joints and sealing - sealing method and classification
CE marking and Declaration of Performance

Installation Requirements

Install ducts level and to correct falls where drainage is required
Support at specified centres - do not exceed maximum hanger spacing
Seal all joints to the declared leakage class
Fire-stop all penetrations through fire-rated elements
Insulate where specified to maintain temperature performance
Test ductwork for leakage before handover

BS EN 12101-3 - Powered fans connected to smoke duct systems
BS EN 12101-8 - Smoke dampers installed within ductwork
BS EN 12101-10 - Power supply to fans and damper actuators
Approved Document B & Building Safety Act - UK regulatory context

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BS EN 12101-7: Smoke and heat control systems. Smoke duct sections