An electrochemical gas sensor system (100) detects the concentration of a harmful gas in a measuring environment (70). The electrochemical gas sensor system (100) contains a voltage generator (19) and an electrochemical gas sensor (1). The electrochemical gas sensor (1) has a sensor housing (2) and a gas inlet (18). A measuring electrode (3), an auxiliary electrode (5), a reference electrode (17), a first generator electrode (13) and a second generator electrode (14) are in an electrolyte liquid (11) in the sensor housing (2). A salt (28) (halide) of a halogen is dissolved in the electrolyte liquid (11). The first generator electrode (13) and the second generator electrode (14) are connected to the voltage generator (19) to form a galvanic source. The galvanic source causes the salt (28) (halide) to react to form a halogen (28′). A defined, largely stable reference voltage potential becomes established on the reference electrode (17).