The concentration of CO2 in fermenting beer is affected by the rate of CO2 formation, CO2 release, and natural agitation. The saturation concentration at 15° C. increases slowly from 0.11% w/w to 0.135% w/w as the fermentation proceeds, while the actual concentration is higher. The bottom conditions seem to prevail throughout the fermenter and, at the end of fermentation, a high level of supersaturation can be obtained, higher than the bottom conditions. A value as high as 0.225% was obtained in a 5-ft. fermenter. Different time-concentration curves are obtained by varying the fermenting conditions and the fermenter height, but in our experiments at 15° C., the CO2 concentration was always found to be uniform at different levels in a given fermenter. However, it is higher in tall fermenters than in shallow fermenters.