BS EN 1366 Quick Guide

A practical introduction to choosing the right fire-resistance test route for ventilation ducts, fire dampers and smoke extraction ductwork.

What is BS EN 1366?

BS EN 1366 is a series of test standards for establishing the fire-resistance performance of service installations. It is not a single product approval and the words “to EN 1366” do not, on their own, define a compliant ductwork system.

The relevant part depends on what the system is intended to do, where it runs, how it is installed and which tested or classified construction is being proposed.

The sections currently covered here

A quick route to the right section

• Normal ventilation duct requiring fire resistance: begin with EN 1366-1.
• Fire damper at a fire-resisting separation: begin with EN 1366-2.
• Smoke extraction duct passing between fire compartments: investigate EN 1366-8.
• Smoke extraction duct remaining within one fire compartment: investigate EN 1366-9.

This is only a starting point. The route must be checked against the project strategy, system evidence and the actual installation.

What evidence should be checked?

1. The required function, classification and fire-resistance duration.
2. The applicable test report, classification report and field-of-application evidence.
3. Duct material, construction, dimensions, joints, pressure and orientation.
4. Supports, restraint, penetrations, fire stopping and protection system.
5. Whether every proposed variation remains within the evidence.

Who decides whether insulation performance is required?

The required fire-resistance performance—including whether insulation (I) is needed and for how long—should be defined by the project fire strategy and specification. This is normally coordinated by the fire engineer, system designer or responsible specifier and accepted through the project approval process.

The decision depends on the duct or damper function, the fire-resistance period of the compartment construction, the route through the building, protected escape routes and the consequences of heat transfer to adjacent materials, services or occupants. The tested and classified system evidence then determines how that performance may be achieved, including the permitted protection or insulation construction and installation details.

A supplier can help match a proposed system to the stated requirement, but should not invent the requirement or assume that a general “fire-rated” description automatically includes insulation performance.

Related smoke-control standards

BS EN 12101-13:2022 concerns pressure differential smoke-control systems. It is relevant to some projects but is not part of the EN 1366 fire-resistance test series.

For the reviewed technical pages currently available, visit the Standards Library.

When dimensions exceed the available evidence

Do not simply scale a tested construction beyond its permitted dimensions. Possible routes may include a battery of smaller ducts, a revised route, another evidenced system or a project-specific technical appraisal acceptable to the approving authority. The smoke-control design, pressure duty, structural support and installation details must all be checked.

For answers to common questions about oversized ductwork, classifications, dampers, access and kitchen extract systems, visit the Frequently Asked Questions.