Inert substances (inert = idle, uninvolved) are understood to mean inert substances that they do not participate in certain chemical processes because they contain no oxygen. These are almost all gases (noble gases), except the very reactive oxygen, In viticulture these are for example nitrogen and carbon dioxide which are often used as protective gases against an undesirable oxidation be used in wine containers. This will, for example, the Kahmigwerden (Wine error) prevented. So-called inert gas mixtures are produced by combustion of combustion gases and then contain no oxygen, but nitrogen and carbon dioxide. These mixtures are less expensive than, for example, pure nitrogen, but it is preferred.
There are bottling plants at the bottling before closing the bottle whitespace (Headspace) fill with inert gas to exclude oxidation. This is especially true when using screw caps important because here the amount of oxygen in the space is much larger. In the so-called inner sealing closures, such as cork (whether natural or plastic) has long been used for sealing under vacuum, because this too high pressure in the head space is prevented by the insertion of the cork (too high pressure could lead to pushing out). The closure under vacuum is now also possible with screw caps. Australia also uses snow-dropping, which adds dry ice (solid carbon dioxide). When the dry ice is in contact with the wine, it evaporates immediately, pushing the air out of the neck of the bottle. Thereafter, the closure is done immediately. See also on this topic oxidation. oxygen management and closures,