The Dunbrik A1 Flue Liners (previously known as class one flue liner systems * ) are ranges of components for the construction of domestic chimneys suitable for domestic fires and stoves. Householders can burn coal and prepared wood or install any domestic gas fire including flame effect fires.
The flue liners are made in four sizes to suit a range of fireplace openings and for stove connection.

Dunbrik concrete liners are manufactured from kiln burnt aggregate and Portland cement and are designed to withstand repeated temperature fluctuations. They are made with tongue and socket detail for ease of construction.

Dunbrik also supply liner sealant, chimney void infill, fireplace lintels, firebacks, chimney pots and terminals.

European Standard EN1857 - Type A1 (T600 N1 D 3 G)
Flue liners have been tested to designation Type A1 having passed in the following classes

Temperature class T600 (Operating temperature 600 degrees, heat stress tested to 700 +/- 50 degrees) Gas tightness class N1 (negative pressure test at 40 Pascals) Condensate resistance class D (Dry flue conditions) Corrosion resistance class 3 Sootfire resistance class G (heat shock tested to 1,000 degrees for 30 minutes)

UK Building Regulations 2000 ADJ 2002
Dunbrik Type A1 flue liners exceed the standard set in ADJ of T450 N2  

* Note: The designation "Class One" for domestic chimneys has been superseded by the European Standard designations based on testing standards resulting in classes achieved, abbreviated to flue liner "types" The highest classes for temperature and gas tightness are A1 N1.