This European Standard specifies the materials, dimensional and performance requirements for precast concrete flue blocks as defined in clause 3 for use in system chimneys. The flue blocks may be of single wall or multi wall construction. The standard does not apply to flue blocks with back ventilation. The standard also specifies a type of flue block to dimensionally co-ordinate with masonry unit coursing height, referred to as a type B (Bonding block). This European standard also applies to storey-height and flue blocks reinforced for handling. NOTE 1 Classes in this standard are not derived from conditions referred to in article 3.2 of Directive 89/106/EEC, and should only be considered as technical classes in the sense of Commission Guidance Paper E `Levels and classes in the Construction Products Directive'. NOTE 2 Any reference to the term flue blocks implies both flue blocks and their fittings, except where otherwise indicated.