Fart is the waste gas discharged by the body, mostly carbon dioxide, hydrogen and methane. Fart is produced because some foods we eat are not decomposed. The undecomposed parts, including fiber and sugar, become food for Escherichia coli. Escherichia coli is discharged after a full meal, and these gases accumulate in the body, causing air pressure. Too much pressure will be pushed out of the body, forming a fart.

The amount of fart is related to people's diet. Some people like to eat onions, ginger, raw garlic, potatoes, sweets, beans and pasta. Because these foods contain substrates that can produce a lot of hydrogen, carbon dioxide, hydrogen sulfide and other gases, the exhaust gas often increases greatly after eating, and fart constantly.

The amount of fart is also related to the strength of human digestive function. When indigestion occurs, intestinal bacteria ferment rapidly, which is easy to produce gas and make people fart. Investigation shows that a person farts about 14 times a day. Every day, everyone releases about 500 ml of waste gas.