more preferably 3 or less where percentages are based on the weight of the activated carbon even at add on levels of as low as 0 1 of the weight of the activated carbon the fluorocarbon treatment has been found effective preferably the add on weights are in the range between 0 1 and 5 of the weight of the activated carbon and more preferably in the range between 0 1 and 3 a cross linking agent such as a polyisocyanate cross linking agent can be incorporated into the mixture to improve the durability thereof in one preferred embodiment the treatment process is conducted in several steps first activated carbon is impregnated with a solvent such as water acetone or alcohol so that solvent molecules occupy the internal pores responsible for gas adsorption next a solution or emulsion containing the fluorocarbon compound s is brought into contact with the activated carbon by immersion spraying or fluidized bed application the fluorocarbon molecules cling to the surface of the activated carbon since solvent molecules are blocking the internal pores finally the treated carbon is dried at elevated temperatures to evaporate the solvent from the internal pores of the carbon typically temperatures of about 100 u00b0 c to about 400 u00b0 c are suitable for this purpose although temperatures of about 100 u00b0 c to about 200 u00b0.