Performance Criteria

The Building Regulations Approved Document B gives detailed guidance on fire safety. This document sets out time periods for Stability, Integrity and Insulation for various compartment walls and floors in a building.

Ducts which penetrate the compartment walls and floors must achieve the same fire resistance as the compartments through which they pass.

Stability

The ability of ductwork – and crucially its support system – to remain intact and fulfil its intended function for a specified period of time

Integrity

The ability of ductwork to remain free from cracks, holes or openings outside the compartment in which the fire is present for a specified period of time

Insulation

The ability of ductwork to maintain its separate function without developing temperatures on its external surface, outside the compartment in which the fire is present, which exceed:

140°C (284°F) as an average above ambient
and / or
180°C (356°F) as a maximum above ambient at any one point

For kitchen extract ductwork (Duct A) these limitations also apply to the internal surface of the duct within the compartment in which the fire is present.