The invention relates to a method and a device for determining the gas permeability of barrier coatings (1) in the region of container walls (2). A quantity of gas to be analysed emerging from the region of the wall of the container into an analysis chamber that is at least partially defined by the barrier coating is measured in said analysis chamber (8). Before entering the analysis chamber, the gas to be analysed is located in the region of the wall. The measuring element can be integrated into a coating device for the container. To this end, a testing device provided with the measuring element is arranged in the transport direction of the container behind the coating device.