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	Performance Criteria. The Building Regulations (1991) 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 have passed. Stability - The ability of a duct and the support system to remain intact and fulfill their intended function for a specified period of time. Integrity - The ability of a duct 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 a duct to maintain its separate function without developing temperature on its external surface, outside the compartment in which the fire is present, which exceed: i) 140°C as an average above ambient and/or ii) 180°C 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. For Smoke Extract systems ductwork must retain at least 75% of its cross sectional area when tested to BS476 Part 24.   The design of fire resistant ductwork of all types is described in BS5588 Part 9. This document requires the ductwork to be tested in accordance with BS476 Part 24: (1987). BS476 Part 24 describes the method for testing ductwork to establish time periods for stability, integrity and insulation. The testing covers the types of fire exposure, Duct A (Fire Outside) and Duct B (Fire Inside and Outside). Duct A (Fire Outside)   Duct B ( Fire Inside) <-Previous Page | Next Page->