Fuel cell unit and method for operating said unit

The system has an arrangement (1) for producing hydrogen with a reformer (2) and several gas cleaning stages (3). A gas burner (5) with an exhaust gas feed (4) heats the reformer. A polymer electrolyte membrane or PEM fuel cell (6) has connections (7, 8) for feeding in oxygen and the hydrogen produced by the arrangement. The exhaust gas feed of the gas burner is connected to the oxygen feed connection of the fuel cell. AN Independent claim is also included for the following: a method of operating an inventive system.