There are two things you can use to tap a beer keg: party pumps and gas taps. Party pumps introduce oxygen and bacteria into the keg, which affects the taste of beer because of the oxidation taking place. Kegs using party pumps should be used within 18-24 hours in order to avoid unpleasant flavor. For gas pumps it is recommended to use a mixed gas (nitrogen-CO2) to avoid beer getting overcarbonated. Gas pumps are able to preserve a keg for 120 days with proper cooling. Kegs are usually placed in cold water or a bucket of ice to keep the beer cold. To pour beer in ideal temperature inline beer chillers may be used, which use their own air compressor to pressurize kegs.