This British Standard specifies requirements for components which, when assembled in accordance with BS8303 , form the setting for inset open fires of nominal sizes 400mm and 450mm (see Figure1). Clause 3 specifies requirements for firebacks for inset open fires without boilers or underfloor air supply used with solid fuel. Clause 4 specifies requirements for prefabricated fireplace surrounds and hearths and excludes constructional hearths at floor level (see Figure1). Clause 5 specifies requirements for precast, reinforced concrete throat-forming lintels, excluding those designed to form part of a complete appliance. NOTE1 Lintels conforming to this British Standard are suitable for use as load-bearing supports for brickwork. NOTE2 Requirements for fireguards are specified in BS8423 .