Hydrogen is one of the most important chemical products, and it is used in a wide series of industrial fields: chemical, petrochemical, metallurgic, as well as in energy applications. Hydrogen demand in all these fields is continuously growing. Nowadays hydrogen is mainly produced from fossil fuels via processes such as steam reforming, partial oxidation, and gasification. All these processes lead to the production of an H2 containing gas stream (synthesis gas) from which hydrogen has to be separated. Thin-film palladium membranes are one of the most promising technologies for the separation of hydrogen from synthesis gas. In this book, palladium films were deposited above stainless steel porous supports using the electroless plating (ELP) technique. The supports have a 0.1 µm filter grade. Two different geometry (disc sheet and tubes) were used. Finally, in this book, the detailed design of a permeability testing unit is reported, including the fluid dynamic, thermal and mechanical dimensioning, the selection of materials and equipment, and some safety considerations. The sketches of the two permeation cells (for the two different membrane geometry) are also reported.