The present invention relates to a process for detecting a leak in a package. The process comprises preparing a package by covering at least a portion of an O2-sensitive product with a multilayer film comprising (i) a leak-indicator layer in which a O2-sensitive indicator is present throughout the leak-indicator layer; and (ii) an O2-barrier layer outward of the leak-indicator layer. A low O2-environment is provided within the package. The leak-indicator layer is then illuminated with light containing a wavelength absorbed by the O2-sensitive indicator, so that the O2-sensitive indicator produces an emission of radiation in an amount inversely proportional to a level of O2 present with the O2-sensitive indicator. Then the multilayer film is scanned while the O2-sensitive indicator is emitting radiation, the scanning being carried out by sensing and comparing the amount of radiation emitted from at least two different regions of the multilayer film.