Fuel cells are considered for various applications as well as in connection with the use of several types of energy feedstocks, both fossil and renewable. Large and very particular challenges arise from the design of the fuel gas supply in connection with envisioned applications and different sorts of fuels. The design of the fuel gas supply must meet the requirements posed by the type of raw fuel, the conceived application and the type of fuel cell employed. In this work, the resulting large number of possible combinations is summarized by a graph, i.e., the "fan". The graphic description is explained by means of selected examples.