This European Standard is the product standard for insulating glass units, which defines insulating glass units, and ensures by means of an adequate evaluation of conformity to this standard that: -- energy savings are made because the U-value and solar factor do not change significantly; -- health is preserved because sound reduction and vision do not change significantly; -- safety is provided because mechanical resistance does not change significantly. It covers additional characteristics that are of importance for trade. Marking conditions are included. The main intended uses of the insulating glass units are installations in windows, doors, curtain walling, roofs and partitions where there exists protection against direct ultraviolet radiation at the edges. NOTE In cases where there is no protection against direct ultraviolet radiation at the edges, such as structural sealant glazing systems, additional European technical specifications should be followed. See Bibliography [2] and [3]. This Part of this standard, which is inextricably bound up with the other Parts of the standard, covers: -- the gas leakage rate by testing; -- the gas concentration tolerances; as one means of verifying whether a product made in accordance with its system description, conforms with the relevant aspects of the definition of insulating glass units.