What is the cask breather argument about?
When a cask is being emptied over a few dozen hours Carbon Dioxide (CO2) is released from solution in the beer into the space above the beer. However this is a gradual process as during opening hours the spile hole will be open to atmosphere and there is plenty of opportunity for the ordinary atmosphere from the cellar to enter the cask as the beer is tapped faster than CO2 comes out of solution.
