A technique of thermal vacuum desorption of charcoal, used in passive dosimeters to enrich organic pollutants of toxicological importance, is described. It combines the advantages of the classic procedure of using highly active charcoal followed by solvent desorption and the environmental one-step procedure of analyzing the whole thermally desorbed sample. For pollutants such as trichloroethylene, tetrachloroethylene, ether, benzene and ethanol, the recovery and reproducibility are satisfactory. The unexpected decomposition of halothane and ethylacetate at higher temperatures is caused by the catalytic activity of the charcoal, but this can be tolerated under constant operating conditions.