Method for operating a gas generating device for a fuel cell

The invention relates to a method for operating a gas generation device in a fuel cell system with at least two gas generation units arranged in series, through which a feedstock stream flows, having a first and second rated power Pnenn_1, Pnenn_2 and a first and second predetermined operating temperature Tnenn_1, Tnenn_2, wherein the first gas generation unit has a lower thermal mass compared to the second gas generation unit. According to the invention, it is proposed that during a start-up phase only the first gas generation unit is operated, whereby the first gas generation unit is operated at a power Pstart_1 > Pnenn_1, and after completion of the start-up phase at least the second gas generation unit is operated.