The goal of this paper is to study and understand the influence of gas flows within a solid mass of waste, treated by a composting process. Composting is an aerobic biological treatment of the organic matter contained in wastes. It has for goal to stabilize and to hygienize this organic matter and is divided into two principal phases: 1.The first one, called the "active phase", mainly develops degrading reactions of the organic matter using , releasing and , and leading to a fast increase of the temperature, all this attenuating by approaching the second phase, 2.The second step is called the curing phase where reactions of biosynthesis of organic macromolecules mainly take place. The strong microbiological activity which reigns within the active phase, as well as the geometrical characteristics of the reactor, generate, by the intermediary of the gas flows, many coupling between biological phenomena, heat and mass transfers. This is why a thorough study of these flows is undertaken in order to better understand these interactions. On the industrial platforms, wastes are laid out in bins or wind-rows subjected to natural or forced ventilation. In case of forced ventilated processes, air is injected or sucked through the ground of the reactor. In all cases, air circulates in the solid mass, thus activating the biological degradation of the organic matter. During this work a bin composting process with positive forced ventilation has been studied. The bases of the mathematical model are detailed in this paper. Experimental methods of measurement of the temperature field and of the gas flow characterization are also presented. The collected data base will be used to test and improve the mathematical model used for the numerical modeling of the studied composting process.