The invention relates to a method and to a device for discharging used operating media of a fuel cell (1) in a fuel cell system (20), at least some of which are explosive, comprising a sensor unit (30) for examining the operating media discharged from an operating space (27). In order to discharge the used operating media from the fuel cell system independently of the operation of the fuel cell system and taking safety regulations into account, a mixing zone (32) is provided for mixing the operating media with a scavenging medium (28) to obtain waste air (33), wherein the operating space (27) is closed by a fan (29), and the sensor unit (30) is disposed downstream of the mixing zone (32), viewed in the flow direction of the waste air (33).