Your Body The Living Truth!
 

Interesting Fact:

It is a known fact that bacteria in the intestine (which is normal) contribute to the stinch of our human feces. It contains actual gases caused by carbohydrate residues from foods like vegatables and beans. This bacteria can produce 8.5 liters of gas a day, but only ejects little.
It is also known that in the presence of oxygen these gases can be ignited! A case once happened during an intestinal surgery and the colon was ruptured!

Resource: Foundations In Microbiology