The operation of vacuum carburizing plants suffers from the production of unwanted byproducts like tarry hydrocarbons and soot. in order to identify mechanisms which influence the amount and the composition of these byproducts, the pyrolysis of commonly used gaseous hydrocarbons has been investigated Under the conditions of vacuum carburizing of steel. Purposely, this investigation included a close look at the interaction of the pyrolysis reactions in the gas phase with the Surface reactions leading to the carburization of the steel. Simulation results for the homogeneous pyrolysis of acetylene Under vacuum carburizing conditions obtained with our Own model are compared with measurements and with results received with commercially available modeling tools. Furthermore. experimental results of the vacuum carburizing of steel are presented and compared With simulation results. The paper focuses on the applicability of the e own model and of commercial software tools for process simulation required for optimizing the vacuum and low pressure carburizing of steel.