Selected experiments were performed at the TAMARA waste incineration pilot plant with a view to identify the formation mechanism of chlorinated aromatic compounds during dust separation by fabric filters at temperatures above 200 degrees C, Significant formation of chlorinated aromatic compounds studied from precursors possibly contained in the flue gas could not be proven in the experiments performed. Formation of chlorinated aromatic compounds was compared with carbon conversion in the filter cake. According to balancing, the fraction of converted carbon that is found in the chlorinated aromatic compounds amounts to a few percent at a temperature of 240 degrees C and is constant in the first approximation. Chlorinated aromatic compounds are generated from the fine particulate residual carbon of the fly ashes, Therefore, a de-novo synthesis has to be postulated as mechanism. (C) 1997 Elsevier Science Ltd.