NBN EN 1858+A1:2011

This European Standard specifies the materials, dimensional and performance requirements for precast concrete flue blocks as defined in Clause 3 for use in chimneys. The flue blocks may be of single wall or multi wall construction. The standard does not apply to flue blocks with back ventilation.
This standard does not cover products designated wet (W) in conjunction with corrosion class 3.
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 Any reference to the term flue blocks implies both flue blocks and their fittings, except where otherwise indicated.