Where does the fart come from?
From gas in the gut. The gas in the intestines comes from the air we swallow, the gas that penetrates into the intestines from the blood, the gas from chemical reactions & gas from the bacteria in the stomach.
What is the compartment compartment?
Varied. The more air you swallow, the more nitrogen content in the fart (oxygen from the air is absorbed by the body before it reaches the intestine). The presence of bacteria and chemical reactions between stomach acid and intestinal fluid to produce carbon dioxide. Bacteria also produce methane & hydrogen. The proportion of each gas depends what you eat, how much air is swallowed, the type of bacteria in the intestine, how long we hold the fart.
The longer hold the fart, the greater the proportion of nitrogen, because other gases are absorbed by the blood through the intestinal wall. People who eat it rush oxygen levels in the fart more because his body did not have time to absorb oxygen.