In a wide range of industries, process gases sometimes have to be cleaned at great expense. For example, compressed air must be de-oiled or hydrogen from a cracker must be cleaned of the accompanying gases using pressure swing adsorption. Other important process gases are helium (He), ethene (ethylene, C2H4), acetylene (C2H2), carbon dioxide (CO2), carbon monoxide (CO). These are just a few examples from the wide-ranging world of process gases, and many cleaning steps are based on adsorption on activated carbon.