- Method for detecting and quantifying leaks in a gas network under pressure or vacuum, the gas network comprising: - one or more sources of compressed gas or vacuum; - one or more consumers or consumer areas of compressed gas or vacuum applications; - pipelines or a network of pipelines to transport the gas or vacuum from the sources to the consumers , consumer areas or applications; - a plurality of sensors providing one or more physical parameters of the gas at different times and locations within the gas network ; characterized in that the method comprises the following steps: - a start-up phase during which the aforementioned sensors are calibrated before use; - a training or estimation phase determining a physical model or mathematical relationship between measurements of a first set of sensors and a second set of sensors based on physical laws using estimation algorithms; - an operational phase where the established physical model or mathematical relationship between the measurements of the first set of sensors and the second set of sensors is used to predict leaks in the gas network ; wherein the operational phase comprises the following steps: - reading out the first group of sensors ; - calculating or determining the value of a second group of sensors from the readings from the first group of sensors using the physical model or mathematical relationship; - comparing the calculated or determined values of the second group of sensors with the read values of the second group of sensors and determining the difference between them; - determining, on the basis of a residual value analysis, whether there is a leak in the gas network ; - generating an alarm and/or generating a leakage rate and/or generating the corresponding leakage cost if a leak is detected. - one or more sources of compressed gas or vacuum; - one or more consumers or consumer areas of compressed gas or vacuum applications; - pipelines or a network of pipelines to transport the gas or vacuum from the sources to the consumers , consumer areas or applications; - a plurality of sensors providing one or more physical parameters of the gas at different times and locations within the gas network ; - a start-up phase during which the aforementioned sensors are calibrated before use; - a training or estimation phase determining a physical model or mathematical relationship between measurements of a first set of sensors and a second set of sensors based on physical laws using estimation algorithms; - an operational phase where the established physical model or mathematical relationship between the measurements of the first set of sensors and the second set of sensors is used to predict leaks in the gas network ; - reading out the first group of sensors ; - calculating or determining the value of a second group of sensors from the readings from the first group of sensors using the physical model or mathematical relationship; - comparing the calculated or determined values of the second group of sensors with the read values of the second group of sensors and determining the difference between them; - determining, on the basis of a residual value analysis, whether there is a leak in the gas network ; - generating an alarm and/or generating a leakage rate and/or generating the corresponding leakage cost if a leak is detected. <EOS>