After the coal had been stored on the site in a coal bunker or coal shed, they were heated in this area without oxygen. In this process, various gases rise and are collected in pipes and collecting tubes. These gases were taken to the (5a) purification house. The coke, waste product in the gas extraction process, was transported to the steel mill.
The building has buttresses and some decorative masonry on all walls. The buttresses ensure the firmness of the facades. The combination of windows, consisting of many small window frames, the double wooden doors, also equipped with small window frames and the buttresses give the building a stately industrial character. Both on the outside and inside there has been changed several times. For example, in 2017 there were no intermediate floors available, whereas in the past there was. The roof is supported by an internal truss construction. The natural ventilation space between the upper and lower part of the roof surfaces is characteristic.