The incineration of Municipal Solid Waste generates dangerous and toxic end products like fly ashes containing chlorine at high concentration resulting a great difficulty for their treatment and valorisation. In the present work, a radio frequency (13.56 MHz) low pressure plasma reactor has been developed for study the dynamic desorption of chlorinated compounds. The chemical analysis of effluents was performed by gas chromatography and mass spectrometry for the detection of low concentration compounds. Mass spectrometry analysis allows the monitoring of chlorinated compounds and points out the positive effect of the plasma on its desorption from the matrix. The hydrogen addition leads to the decrease of the reactive chlorine species and simultaneously the increase of HC1 formation. Experiments with a second fluidized bed of CaO were carried out in order to evaluate the competition between the chlorine trapping in HC1 or in CaCl2.