Inspection method for controlling an opening duration (OD) of an outlet valve (142) of a liquid container (140) in an anode exhaust gas section (124) of a fuel cell system (100), characterised by the following steps:
- opening the outlet valve (142) to drain liquid (F) from the liquid container (140),
- recording the anode pressure (AP) in the anode exhaust gas section (124) at the time of opening the outlet valve (142),
- setting an anode pressure reference value (APR) based on the recorded anode pressure (AP),
- further monitoring of the anode pressure (AP) during the opening duration (OD) of the outlet valve (142),
- determining an anode pressure deviation (APA) of the monitored anode pressure (AP) from the set anode pressure reference value (APR),
- closing the outlet valve (142) when the determined anode pressure deviation (APA) exceeds a deviation threshold (AG).