Become a Patron!

How much do you know about your farts?

Due to an unfortunate episode involving the Lab Dog, the Spawn and I found ourselves deeply involved in a conversation on the contents of farts and also argued for a while over the origin of the discrete sound produced by our canine companion. This one was quite silent but deadly.

[WPGP gif_id=”1814″ width=”600″]

The origin of the fart

Farts, or flatulence, is produced in the intestines by bacterial fermentation.  In short, bacteria are breaking down food and releasing gas in the process. The gas then travels along the large intestine and the rectum and finally arrives at the anal sphincters to be released out into the big wide world for a wide-spread enjoyment of both sounds and odor.

As most of you probably have noticed, farts can smell very differently, mostly depending on the food you have eaten, but many other factors can also play a role such as illness, stress and hormonal effects. However,  let’s start with some basic flatology for the upcoming fart connoisseur.

Doctor Anna fart

Know your fart

Many of you probably want to know how to achieve that fantastic ripe odor that frequently seems to leak out of someone’s butt in the subway during rush hour or in the checkout line at the supermarket.  You see, despite its devastating effect, I’m pleased to confirm that this effect is actually not that hard to obtain. Generally, the more volatile sulfur compounds in the end product, the riper the odor.  The solution is thus to eat a lot of sulfur-containing compounds such as proteins which leads me to think that bodybuilders do it right: loads of proteins and then total release when squatting.

But “ripe odor” is a diffuse concept and the serious connoisseur calls for a better classification of these everyday debacles. Let’s get serious and dive into the finer details of the gaseous content of flatulence.

Doctor Anna Boom

Generally, we can split the bouquet of farts into three main categories of odor which makes fart-classification much more precise. There are strong correlations between three particular compounds and the farty-smell. The first is hydrogen sulfide (H2S), which is the same compound that is produced by marine anaerobes (bacteria that can live without oxygen) when the water has turned anoxic (no oxygen). The second one is methyl mercaptan (MM), and the third dimethyl sulfide (DMS).  The smell of each of these compounds has been delightfully described as decomposing vegetables (MM), unpleasantly sweet radish (DMS) and rotten eggs (H2S).

In order for you to control your odor development, it might be interesting to know that the smell can increase if there are feces (poo) in your rectum (the last part of your intestine).

The smell of farts: Decomposing vegetables (MM), unpleasantly sweet radish (DMS) and rotten eggs (H2S).

Doctor Anna gas mask

How many farts are normal?

It is normal to fart between 500-1500 ml gas in 24 h, and about 8-20 times per day. This makes about 5-350 ml per fart. I am not entirely sure that this statistics is a useful tool in determining how normal your farting is since I have yet to meet anyone who has measured the volume flatulence released per day outside a lab. Walking around with a tube up your butt just seems very unpractical.

Another interesting observation is that we fart more in the mornings than in the evenings, probably because of the increased activity of the intestines after the nightly fasting. Flatulence can in rare instances be caused by the swallowing of air (aerophagia) such as when chewing gum, but this flatulence does not smell since it is made up of the normal composition of air. But, please, don’t let that be a reason to chew gum with your mouths open. It is tremendously annoying.

Know your fart!

The sound of farts

The farting sound is produced by the vibration of the anal sphincters and the loudness and frequency of the sound determined by the tension of the sphincters, a bit like the lips of a trumpet player. Another quite neat effect that is unique to the naked-butt-cheeked (mostly) humans is that the sound can sometimes be exaggerated by a larger volume of gas being pushed up through the closed buttocks, like making a trombone out of a trumpet. This can particularly be observed when seated and more specifically when the classroom is silent.

This is a wonderful 7-tone fart symphony by Loz for you to enjoy:

Farts, illness, and accidents

Methane -and hydrogen gas make up a large portion of flatulence and are both extremely flammable, something that a patient at the Tokyo Medical Hospital experienced first hand when she farted during a laser surgery and caught fire. The patient is luckily reported to be OK.

The proportion of methane and hydrogen gas can vary depending on medical conditions. If you are obese, have irritable bowel syndrome (IBS) or constipation, you have proportionally more methane than hydrogen in your farts.I have endometriosis and IBS so I expect to be tipping towards the methane side of things. What about you?

Sci Hard!

Doctor Anna
Become a Patron!

ps. Mercaptoethanol: covering scientist’s flatulence since 1953.

More interesting stuff from Doctor Anna

Science Jokes for Intellectual Badasses

How I Realized that my Sexlife is Quite Vanilla


Tangerman, A. (2009). “Measurement and biological significance of the volatile sulfur compounds hydrogen sulfide, methanethiol and dimethyl sulfide in various biological matrices”. Journal of Chromatography B 877 (28): 3366–3377.
Tomlin, J; Lowis, C; Read, NW (1991). “Investigation of normal flatus production in healthy volunteers.”. Gut 32 (6): 665–9. doi:10.1136/gut.32.6.665. PMC 1378885. PMID 1648028
Levitt, MD; Furne, J; Aeolus, MR; Suarez, FL (1998). “Evaluation of an extremely flatulent patient: case report and proposed diagnostic and therapeutic approach.”. The American Journal of Gastroenterology 93 (11): 2276–81. doi:10.1111/j.1572-0241.1998.00635.x