It is known that removal of impurities from liquids or gases by Activated Carbon is by adsorption. But only a thin layer if molecules is enough to neutralize the residual attraction of the outer carbon atoms, which then cannot be adsorb any further molecules and carbon is said to be exhausted. It is however possible to make carbon porous. In this way many countless are created and internal surface area is increased. Many more carbon atoms are then exposed to the surroundings resulted in more molecules from surroundings can be attracted. The carbon is more active and hence called Activated Carbon. One gram of ground carbon has an external surface area of 2 to 4 square meters, whereas when carbon has been activated this one gram of carbon may acquire an internal surface area of more one thousand square meters.