Fart lighting is the practice of igniting the gases produced by human flatulence, often producing a flame of a blue hue, hence the act being known colloquially as a "blue angel", "blue dart", or in Australia, a "blue flame". The fact that flatus is flammable, and the actual combustion of it through this practice, gives rise to much humourous derivation. Other colors of flame such as orange and yellow are possible with the color dependent on the mixture of gases formed in the colon.
Although there is little scientific discourse on the combustive properties of flatus, there are many anecdotal accounts of flatus ignition and the activity has increasingly found its way into popular culture with references in comic routines, movies, and television; including cartoons.
Methane burns in oxygen forming water and carbon dioxide often producing a blue hue (ΔHc = -891 kJ/mol), as:
CH 4(g) + 2O 2(g) → CO 2(g) + 2H 2O(g)
Hydrogen sulfide also combusts (ΔHc = -519 kJ/mol) to
2H 2S(g) + 3O 2(g) → 2SO 2(g) + 2H 2O(g)
The odor associated with flatus is due to hydrogen sulfide, skatole, indole, volatile amines and short-chain fatty acids. These substances are detectable by olfactory neurons in concentrations as low as 10 parts per billion, hydrogen sulfide being the most detectable.
Some of the gases are produced by bacteria which live in symbiosis within the large intestines of humans and other mammals. The gases are created as a by-product of the bacteria's digestion of food into relatively simpler substances. The oxygen and nitrogen component of flatus can be accounted for by aerophagy, while the CO2 component results from the reaction of stomach acids (HCl) with pancreatic bile (NaHCO3).
Because the methane, hydrogen sulfide, and hydrogen present are flammable, igniting the resulting gases can result in burns or explosions as well as the desired flame. Clothing, hair, or skin may catch fire and sensitive tissues can be damaged.
Fart lighting has been a novelty practice primarily among males or college students for decades.
In popular culture
Many find a comedic value in fart lighting and the activity is increasingly represented in pop culture possibly because "for adults, the allure of the vulgar is regressionary and often secretly pleasurable."
In the film South Park: Bigger, Longer & Uncut, one of the main characters, Kenny, dies due to the burns caused by lighting a fart on fire after watching it in the fictional film Terrance and Phillip: Asses of Fire. This causes him to be sent to Hell and allows for the war against Canada to proceed on Earth.
In The Young Ones episode "Cash", the guys' house explodes when Mike tries to light a cigar following Vyvan giving birth to an exceptionally large fart.
In May 2000, a U.S. patent was issued for a "Toy gas fired missile and launcher assembly", a product that would allow one's "colonic gases" to be stored for later ignition to "fire the missile into space."
^Zanakis, Michael F.; Philip A. Femano (2 May 2000). "Toy Gas Fired Missile and Launcher Assembly". U.S. Patent Office, Patent number: 6055910; Filing date: Jun 1, 1998; International Classification - F42B 406. Retrieved 2008-01-10.