Abstract: A method for detecting a leak in a resilient, semi-hard and hard package includes a test gas supplied to the package to subject the contents of the package to a first pressure. The package is then maintained for a predetermined time in a chamber having a gas pressure, and the presence of gas is detected in a measuring space in gas flow relationship with the chamber by a detection apparatus. In order for the method to be rapid enough to be suitable for detecting very small holes in packages and for use in production plants without a change in their operating rate, a hydrogen gas having a hydrogen gas concentration from 0.0001-6% by volume is used as the test gas supplied to the package, and the hydrogen gas concentration of the gas within the chamber is maintained below a reference concentration that is lower than the hydrogen gas concentration in the package immediately after the addition of hydrogen gas to the package.