Every person farts around 14 times a day, which if you think about, is a fairly large number. Quite a lot of the farts happen when we sleep at night. How the farts come out and what they are made up of depends on how much air we have breathed in, what food we have eaten, the bacteria composition in our stomach, and how long we actually hold in the farts. Farts are caused by the air trapped in our stomach; it could be air we swallowed, it could be produced by the chemical reactions in our intestines, it could be from the bacteria in our digestive tract and it could be gas seeping into the intestines from our blood. It’s mostly a combination of all of these. A typical fart is made up of 59% nitrogen, 31% hydrogen, 9% carbon dioxide, 7% methane, 4% oxygen and 1% hydrogen sulfide and mercaptans.