Common sources of CO2 include hydrogen and ammonia production, fermentation and collection from geothermal wells. Prior to its use, the carbon dioxide must be purified before being considered suitable for its intended use as a direct food additive to the beverage. Potential contamination of a CO2 supply can occur as the result of natural impurities in the raw gas source not being effectively removed, or from gas contamination during storage and distribution. It is the responsibility of both the gas supplier and the user to take appropriate steps to ensure the quality of the carbon dioxide. Safety and good manufacturing practices for food additives should be applied throughout the process, from production, delivery, and storage to dispense.