Timahdit oil shale was used as a porous medium to characterize the structure of a combustion front propagating with co-current downward air supply. A new 1D experimental device was first calibrated using a model porous medium. With the model porous medium, the front propagates as a plane and horizontal surface while using oil shale the front propagates as an inclined curved surface. The peak temperature was 1100 degrees C; despite the relatively large diameter of the cell ( 91 mm) and the good thermal insulation, the heat losses were estimated at 42% of the heat released by the combustion. The thickness of the front was characterized using a new gas micro-sampling system: the char oxidation and the carbonate decarbonation zones are approximately 10 and 15 mm thick, respectively. The oil formed during the pyrolysis is adsorbed in the porous medium in the course of the experiment, and expulsed from the cell by the end. (C) 2009 Elsevier Ltd. All rights reserved.