Abstract: A gas monitoring system includes a gas-insulated switchgear including a chamber filled with an insulating gas surrounding a high or medium voltage component, a sensor operatively connected to the chamber and adapted to measure a physical property of the insulating gas in the chamber over time, and a computer unit adapted to perform on the sensor measurements a statistical step detection for determining if a jump has occurred and/or a statistical change detection for determining if a change has occurred, whereby the statistical step and/or change detection includes identifying an expected range based on past sensor measurements and checking if a current sensor measurement is outside of the expected range.