This paper presents the principle and testing of a novel technique developed for carburizing processes monitoring. The technique relies upon an experimental device made of a thin iron foil with a carburizing atmosphere on one side and a decarburizing atmosphere on the other. The principle of carburizing control is based on the fact that when steady-state of carbon diffusion is reached across the thin iron foil, the measured mass flux of carbon on the decarburizing side is related to the inflow of carbon into the parts during the carburizing treatment. Hence, as a probe could be inserted directly into a given furnace, it would provide an in situ control facility. The proposed device could then be used for controlling atmospheric or low-pressure (vacuum) carburizing treatments. The results presented here are limited to atmospheric conditions. Nevertheless, they gave the incentive to the researchers to pursue the development of the device to allow for measurements in a low-pressure furnace and to refine the experimental bench to quantify thoroughly the phenomena involved within the foil. (C) 2002 Elsevier Science B.V. All rights reserved.