Carbon Dioxide gas – CO2

Yeast breaks sugar down into alcohol and carbon dioxide gas. CO2 is what makes wine sparkling. But also in so called “quiet wines” (non-sparkling wines) a minimal amount of carbon dioxide is present.
This makes wines more accessible, easier to drink.

If the carbon dioxide gas is easy recognizable this is called frizzante (Italy) or pétillant (France).
If the pressure increases even further to 5-6 bars, it is called spumante (Italy) or mousseux (France).
In the yeast cellar it is a danger as well: it is scentless and drives out oxygen.
That means refreshing the air is essential.