NOVELTY - The device (9) has an air conveying device (13) that is partially driven by an electric motor (16) at a voltage level of a fuel cell, where the fuel cell is surrounded by housing. The air conveying device is arranged in series with another air conveying device (14) that is driven by another electric motor (17) at a low voltage level, where the two air conveying devices are designed as flow compressors and/or side channel compressors. An air filter (15) is arranged in flow direction in front of the latter air conveying device.    USE - Air supply device for a fuel cell i.e. proton exchange membrane fuel cell, in a fuel cell system utilized for providing electrical driving power to a vehicle (all claimed).    ADVANTAGE - The design of the air supply device ensures large pressure loss at an air filter arranged at a suction branch even when one of air conveying devices is in an idle state, thus ensuring supply of filtered air to the fuel cell during regular operation of the fuel cell and/or during driving of the vehicle, while ensuring eventual hydrogen flow to a cathode compartment of the fuel cell. The air supply device is operated during starting or during subsequent restarting of the fuel cell system, thus ensuring removal of the hydrogen leakages in a reliable manner, and ensuring air supply to the housing of the fuel cell, and hence ensuring safe and reliable ventilation of the housing. The air supply device is operated by the low-voltage system of the vehicle, so that starting of the fuel cell is realized using the low-voltage system during an emergency condition, even if high-voltage transmission system is failed. The design of the device ensures simple and safe structure for the fuel cell system, enables operating of the vehicle in an energy-efficient manner, and allows safe operation and efficient control of the fuel cell.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic pneumatic circuit diagram of an air supply device.    Air supply device (9)    High-voltage transmission system (11)    Air conveying devices (13, 14)    Air filter (15)    Electric motors (16, 17)