ABSTRACT The invention provides a method for leakage detection in a device for shaping container preforms, comprising a compressed air system which is connected to a compressed air source and comprises at least two fluidically connected regions that can be separated from each other and/or from the environment by shut-off elements. The method comprises a leakage test run conducted in an automated manner in which at least one of the blocking elements and/or the compressed air supply into the compressed air system is controlled in such a way that it can be determined separately for each region whether compressed air escapes therefrom.