Gas, or flatulence, is the release of excessive amounts of gas present in the digestive tract. Gastrointestinal gas is made up of swallowed nitrogen and oxygen, as well as methane, hydrogen and carbon dioxide. When gases are unable to be digested, they end up being released as flatus. Flatulence gives of foul smell due to sulfur compounds that were released by the body. Gas in the stomach and intestines may cause abdominal pain and distention.