Austrian term (vernacularly "Kerzerlprobe") for a method used very often in the past, but extremely inaccurate and therefore (life-)dangerous, to determine the carbon dioxide content and thus the fermentation status during fermentation in a wine cellar using a burning candle. Already at a concentration of 5 to 7% carbon dioxide content in the air, this is life-threatening for humans due to a first fainting, but the candle only goes out at about 10%. In former times the fermentation gases were also discharged via so-called fermentation grids in the cellar door and/or via the steam pipe (a ventilation shaft). However, this could only be done inadequately without a corresponding mechanical extraction system, because the gas, which is heavier than air, collected at the lowest point of the cellar. See also the section on wine-growing customs.