This Part of BS 476 describes procedures for determining the contribution made by components to the total fire resistance of a structure or other elements used in conjunction with them when subjected to the relevant heating and pressure conditions specified in BS 476-20. This Part provides the requirements for specimen selection and/or its design and construction, the edge conditions, the equipment including any special apparatus or instrumentation, and the procedures and criteria as they apply to components which make a contribution to the fire resistance of a complete assembly. The methods are applicable to suspended ceilings protecting steel beams and intumescent seals for use in conjunction with single-acting, latched timber fire resisting door assemblies.