The oxygen increase is measured in a system of which the test piece forms part. Oxygen can only be transported through the wall of the multilayer test pipes. Therefore, the increased amount of oxygen in the closed system is the result of the functioning of the barrier layer of the test piece. The test unit consists of a supply unit (installed in a installation cabinet), an oven and a drum to support the specimen (length: 20 ±0,5 m). The auxiliary trolley (additionally delivered) is used to transport the specimen. On this trolley the specimen is sterilised and prepared for the test, and then inserted into the heating chamber to perform the test (incl. quick connector to shut double-side off for specimen connection).