The majority of activated carbon used through out the world is produced by steam activation. Steam activated carbon is produced by two stage process. Firstly the material is carbonized and coke is produced. The pores of produced coke are to small, hence, the next stale is a process of enlarging the pore structure so that an accessible internal surface is created. This is achieved by reacting semi product with steam at temperature between 900 C _ 1100 C. At this temperature rate determination factor is the chemical reaction between steam and carbon. This reaction takes place at the internal surface of the carbon removing carbon from the pore walls and thereby enlarging them.

Opening up the pore structure is costly as the yield decreases and extra heat is required. E.g. In the purification of water for the adsorption of small molecules from solution. This carbon is cheaper compare to sugar decolorizing carbon where large molecules are to be removed. Thus, steam activation process allows the pore size to be altered and finally carbon can be made to suit different purposes.