why do farts smell

[jamey2k9]

apologies if this is in the wrong forum

 

 

i've been wonderering why your farts dont smell very bad to you but do to other people?

[insane_alien]

nose deafness, you're so used to the smell of your own farts that you don't mind it any more. although, if you have a particularly foul one you'll still find it smells bad.

[iNow]

Well, I'll be perfectly honest, my farts DO smell bad to me, so I want your problem where you can't smell them!

 

Kidding aside, I think you may mean "why do your own farts tend to smell worse to other people than yourself," which is an interesting question. I don't know for sure, but my first guess is that there is something in our colons and metabolism that makes the scent of our bodily excretions somewhat consistent throughout our lives... some common factor among all farts. If that's the case, then we perhaps simply desensitize to the scent of our own farts through the years, we get used to them, and they are not as noxious. However, when we smell someone else's fart, there are all different kinds of chemicals and compounds that we're not used to, so it is much more profound and striking.

 

Just a guess, above. I am not sure how else to answer, but it's an interesting question. I chose to think of it like body odor... you get used to it over the years, and it's somewhat consistent, so you just don't notice it when it's your own, but it makes your eyes water when it's someone else.

[Royston]

If it was a case of 'getting used to it' though, then surely we'd get used to other family members bottom burps, or odour after a number two, who will have the same diet et.c and which will be experienced on practically a daily basis.

[padren]

While I wouldn't say they ever don't smell pleasant, I've always wondered a bit because there seems to be a bit of a strange underlying positive/negative background evaluation that goes on.

 

I always wondered if it was an evolutionary thing, where they smell worse if you eat things that distress your system or have some other factor compromise your digestive health. Some antibiotics cause mine to be "disturbing" despite not really being that different "odor" wise.

 

But maybe iNow is right. Heck - maybe people became accustom to their own because the ones who didn't ran out of their caves and gotten eaten by saber tooth tigers.

[Mr Skeptic]

No doubt a large part of it is psychology.

 

I found this website that is all about farts: http://www.poopprank.com/fart/index.htm

[iNow]

Maybe it's because, with our own, we know they're coming. We have a "head's up" and can brace ourselves for the impact, whereas with farts from others it's like a sudden slap in the face... surprising and scary. Please tell me if you think this idea stinks.

[arnolp04]

it's the gases given off by fermented food inc hydrogen sulphide

[Chris_25]

Sorry I've gotta quote a line from an Austin Powers Film:

 

"Oh everyone likes their own brand don't they?"

[DrDNA]

Mine are a strong attractant.....................................................................................to dogs mostly.

[CaptainPanic]

So, although it's not literally in the question, I would have expected somebody to state the composition of the gas! Nobody bothered to check wikipedia for "farts"? In stead, everybody just started to share their own smelly experiences... lol. :D

 

So what makes the stink? It has to be a whole range of (gaseous) chemicals in there, because all farts smell different.

 

The gas released during a flatus event frequently has an unpleasant odor which mainly results from low molecular weight fatty acids such as butyric acid (rancid butter smell) and reduced sulphur compounds such as hydrogen sulphide (rotten egg smell) and carbonyl sulphide that are the result of protein breakdown. (Source)

 

And what's the composition of the gas (because the stinky stuff is a very small part of it, but very "present")?

The major components of the flatus, which are odorless, by percentage are:[2]

 

* Nitrogen - 20% - 90%

* Hydrogen - 0% - 50%

* Carbon Dioxide - 10% - 30%

* Oxygen - 0% - 10%

* Methane - 0% - 10% (Same source)

I can produce at least two very distinctive ones: normal and beer-farts

[DrDNA]

I can produce at least two very distinctive ones: normal and beer-farts

 

Ah, yes.

That is a tropical storm for sure.

 

But a category 5 hurricane is a malt liquor (eg, Colt 45, Cobra, Little Kings, etc....), which is probably a category 1 or 2 by itself, PLUS pickled hard boiled eggs.

 

Makes me sick to my stomach just thinking about it......

[John Cuthber]

I thought that this was an old joke

Q Why do farts smell

A for the benefit of the deaf.

But I guess that's not very PC

[rpalado]

No particular reply, but another question to think about.

Normal everyday flatulence is harmless. But I remember hearing on a television program (can't remember which one) but there supposedly is a level of toxicity in "beer farts" that if subjected upon it in an enclosed space in large amounts can actually be fatal.

 

Can anyone confirm that?

[insane_alien]

all farts have a level of toxicity to them, they contain sulphur dioxide, carbon dioxide and traces of methane.

 

all three of those ar toxic.

 

however, the sheer volume of farts needed to become toxic is immense even in an enclosed space. even in a small enclosed space, say a closet, you'd need thousands of epicly massive farters to let one rip and pump it in. the smell would become completely unbearable before there was any actual toxic effect. you'd even be unconcious by then.

 

this is not a situation you are likely to find yourself in.

 

unless your one of those guys with a wierd fetish for it maybe. but even then, where are you going to get thousands of champion farters to fart down a pipe leading to a closet.

[Phi for All]

but even then, where are you going to get thousands of champion farters to fart down a pipe leading to a closet.

I would start with craigslist.

[GDG]

I would start with craigslist.

 

Frat house

[Syntho-sis]

nose deafness, you're so used to the smell of your own farts that you don't mind it any more. although, if you have a particularly foul one you'll still find it smells bad.

 

 

I think there is some other factor involved.

 

If our noses become "deaf", Why is it we can see the same image millions of times, or hear the same sound over and over again?

 

Wouldn't our brains turn theses sensory details off as well?

 

This is just supposition, but smell being the most important sense in the animal kingdom, wouldn't that be one we were constantly aware of innately?

 

But I have noticed that I also become habituated to certain smells given enough time.

 

hmmm...

 

Perhaps, it is our brains deciding that a smell is no longer offensive?

 

For example, when someone first hears heavy metal music it is usually very annoying and loud. But given enough time and listening to the music repetitively, they start to enjoy it.

 

Although, I have never met someone who enjoys the smell of farts.

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unless your one of those guys with a wierd fetish for it maybe. but even then, where are you going to get thousands of champion farters to fart down a pipe leading to a closet.

 

hahahahaha....Yes start with craigslist!

[insane_alien]

If our noses become "deaf", Why is it we can see the same image millions of times, or hear the same sound over and over again?

 

Wouldn't our brains turn theses sensory details off as well?

 

This is just supposition, but smell being the most important sense in the animal kingdom, wouldn't that be one we were constantly aware of innately?

 

well, we depend on our sight and hearing much more than smell, and we do tune out certain information from these senses.

 

take billboards for instance, most people ignore these to the point htey don't see them at all. and we tune out background noises as well such as traffic. we simply don't hear and see these things conciously.

 

since we don't rely on smell that much(unlike a lot of the animal kingdom) stuff gets tuned out from that a lot more often.

[J.C.MacSwell]

There is probably some survival advantage in being more aware of a foreign smelling fart, putting us on high alert, and also for wanting others to smell it first, in a less diluted state. If they and we survive unscathed, we can allow ourselves to become more "accustomed to it" for next time.

[Syntho-sis]

well, we depend on our sight and hearing much more than smell, and we do tune out certain information from these senses.

 

take billboards for instance, most people ignore these to the point htey don't see them at all. and we tune out background noises as well such as traffic. we simply don't hear and see these things conciously.

 

since we don't rely on smell that much(unlike a lot of the animal kingdom) stuff gets tuned out from that a lot more often.

 

Yes, that's a good point, I never considered that.

 

An organism simply becomes habituated to a stimulus.

 

Well, actually it probably slightly more complicated than that haha.

[Carvone]

As a flavour chemist, I can verify that noses can become fatigued to smelling the same aroma repetitively, and when we lose our sensitivity to an odour we are trained to stick our nose into our arm at the elbow joint and smell ourselves to cleanse the olfactory receptors. So with a fart, it could be a case of loss of sensitivity to our own brand, but I also think, as mentioned above, it has a bit to do with being proud of our own brand, at least we are expecting our fart and prepared mentally for it, and can then admire it, while someone elses always hits you off guard.

 

Also, although someone above quoted the composition of a fart, and this may be correct for the major gas constituents (although I am not sure), there are definitely many more odour compounds present in trace amounts. And like flavour compounds, our noses are very sensitive to these trace amounts (parts per million to par per trillion) with much lower sensory thresholds than say methane. Hydrogen sulfide (rotten egg) has a very low sensory threshold. Also different people have differences in sensitivity to different compounds, thus why some farts are detected by others and not you and vice versa.

 

I have often been curious to analyze a fart on the GC-MS, but never gotten around to it. (Kinda gross I guess). Also I figured there would be great variability in the trace aroma compounds in a fart based on many variables such as the foods eaten previously, the microflora in the intestine, enzymes, how much water or ethanol are present to act as solvents, etc. After all, aroma compounds are the small molecular weight fragments broken off of or are the microbial waste byproducts of large molecules such as carbohydrates, proteins and fats.

Edited June 18, 2009 by Carvone
forgot to finish a sentence (oops!)

[jamey2k9]

I cannot believe this thread is still been discussed I posted it in january!

to the point could it be we grow so used to the smell it doesn't bother us that much

[gregzeters]

I think its due to the bile juice that was mixed with the digested food. Maybe..

[fottry55i6]

Farts, or flatulence, smell because it is made up mostly of H2S. The sulfur in it causes the smell.