[en] Amongst chemical decontamination techniques, the foam cleaning process has the advantage of reducing the amount of liquid used, thus limiting the quantity of the chemical reagents and the secondary waste volume. In order to improve this process, it is essential to understand the behaviour of the foam in the vicinity of the contaminated surface. Two methods of study have been initiated. Firstly, the characterization of the liquid film formed on the wall, and secondly, the characterization of the foam bed. Furthermore, our goal is to set up a drainage model which enables a choice of process parameters. Flush-mounted conductance probes have been developed in order to determine the thickness of the liquid film at the surface and the foam liquid fraction. The influence of the foam on the film structure and the interpretation of the thickness measured is discussed. The process studied consists of filling the facility with foam and letting the foam drain once the facility is full. It was demonstrated that the liquid film thickness varies between a few microns and 50 μm and that the value depends on position and time. Furthermore, a strong correlation links the film thickness and the foam liquid fraction. A drift-flux model has been built to describe the drainage of the upstream flow or static foam. The model is solved by using the method of characteristics. Analytical solutions are obtained and the liquid fraction evolution can easily be represented on a single diagram. The parameters of the void-drift closure law have been deducted from the experiments. The comparison to experimental data has shown that the model is well adapted. The laboratory therefore has experimental and theoretical equipment to study any foam. Finally, the model is applied to realistic decontamination configurations in order to present how determine the parameters of the process. (author)