Abstract: This invention relates to a process for determining the state of an electrochemical gas sensor located in an environment with a known and constant concentration of a gas which is to be detected, where said gas to be detected is converted by chemical reaction at a three-phase boundary formed by a measuring electrode, an electrolyte and the gas to be detected, and where a current flowing in an external circuit functions as a sensor signal, whereby for determination of the state of the gas sensor, the external circuit is temporarily interrupted, and during this time the gas sensor is in specific exposure with the gas to be detected, and the resulting transient of the sensor is recorded and evaluated over time after the external circuit is closed.