Oxygen barrier materials made of plastic must be sufficiently thermally stabilized if they are used in a particular piping system as specified in Annex C through I of the certification scheme. They are considered to be thermally stable if the continuous operating temperature (corresponding to a stress duration of 50 years) does not exceed 70 °C.
If manufacturers of plastic piping systems use oxygen barrier materials with a valid DIN certification in accordance with Annex J, it shall be considered as proof of thermal stability.