The human body expels gas on average 14 - 23 times per day totalling about 2 pints in volume, most commonly as a burp. The air which isn't expelled by belching travels from the stomach to the intestines. Some of the gas is absorbed and some more is created by the further digestion of food. What remains is expelled through the anus. Gas is generally made up of carbon dioxide, oxygen, nitrogen, and sometimes methane. Only about 1/3 of people produce methane -- to figure out if you're part of the 33% nation, look at your poopies. in general, do they float? congratulations, you make methane! This doesn't mean your farts smell any more than the other 66% of the world -- methane is odorless. The smell is caused by bacteria.