Beer kegs are a the options preferred for parties and meetings in which the organizers want the job a little easier and make their guests happy. They generally contain about 30 liters of beer, and that frees them from the anguish of thinking whether it would be enough for everyone.
By placing the beer in the barrel is important to carbonate, carbon dioxide is a gas that dissolves easily in beer. That amount of gas is measured in volumes. If a liter of beer is carbonated with 2.5 volumes, means that there are 2.5 liters of CO2 in the beer.