NBN EN 12446:2011

This European Standard specifies the material, dimensional and performance requirements for factory made precast concrete outer wall elements for chimneys including outer wall fittings.
This European Standard covers elements having up to four passages designated to accommodate a combination of flue liners and/or ventilation passages.
This European Standard also relates to storey-height and reinforced outer wall elements.
This European Standard does not apply to structurally independent (freestanding or self-supporting) chimneys constructed using these outer wall elements.
NOTE Any reference to the term "outer wall element" implies both the outer wall elements and their fittings, except where otherwise indicated.