'Elemental' carbon (EC) is used as a surrogate to assess occupational exposure to diesel soot. EC thermal analysis needs complete desorption of organic compounds from the soot particles prior to analysis in order to minimize positive interferences and artefacts. The desorption of the organic compounds can be considered as the major step which influences the reliability of the EC determination. A systematic study was carried out to investigate the different parameters of influence such as desorption temperature, desorption duration, heating rate and type of the sample on the desorption efficiency. It was found that temperature and duration are the major parameters of influence on the desorption efficiency. The influence of the sample load can be seen as a measure of the pyrolysis susceptibility of the sample. An optimized temperature program is proposed.