An electrochemical gas sensor (10) has a housing (20), a working electrode (51), a counterelectrode (52) and a reference electrode (53). The housing (20) has an electrolyte reservoir (30), a gas inlet orifice (21) and at least one gas outlet orifice (22). The electrolyte reservoir (30) is filled with a liquid electrolyte (40). The gas sensor (10) has a counterelectrode carrier (26). The counterelectrode (52) is suspended on the counterelectrode carrier (26) in such a way that the counterelectrode (52) is suspended in the electrolyte reservoir (30) and the electrolyte (40) flows around the counterelectrode (52) on all sides. Preferably, the electrolyte includes (I) a solvent, e.g. water, propylene carbonate, ethylene carbonate or mixtures thereof; (ii) a conductive salt, especially an ionic liquid; and/or (iii) an organic mediator, for example substituted quinones, anthraquinones, etc.