Why does flatus smell the way it does and why does it vary from person to person?
481934
Most of the odour comes from molecules released by bacteria in the gut.  Some are facultative; they can live with or without oxygen.  Some of these release hydrogen disulfide (rotten egg gas.)\n\nOthers are anaerobes; they live only in the absence of oxygen.  Many of these release fatty acids and amines from the larger molecules they digest for food; fats, proteins, nucleic acid, etc.  Some fatty acids are very pungent; some smell like butter, or strong cheese, or dog faeces etc.\n\nThe anaerobes are even pungent if cultured in our laboratory!  When we are culturing from some samples, the stinky ones generally contain anaerobes.  A good sense of smell is very handy in Clinical Microbiology.\n\nYears ago, I read research (that was done in inbred mice strains) showing that the genes of the animal had an influence on the types of bacteria that remained in its gut.  They said this was part of the reason why different strains of mice could recognise close relatives by smell; genes resulted in smells.\n\nI think this explains why different people make different odours, though fed the same foods.
240902
It's true, what you eat affects how it smells, but what you eat also affects skin, urine, sweat, and breath odors.  Limiting extremely pungent = smelly, foods will help. Food like garlic, onions, curry powder, etc.  However garlic is good for you and peppers like jalepenos cause some cancer cells to self destruct. I realize you may not want to hear this from a female but the truth is if who ever is in the position to be smelling/tasting your sperm, they probably like you enough that it doesn't matter.....or if it is the taste that gets to them then have the person use mouth wash or brush their tongue before hand.  It desensitizes the taste buds so it is hard to taste anything.
695611
Some it doesnt smell, some it does depending on what you eat.\n\nhttp://sexuality.about.com/od/sexualhealthqanda/f/vaginaltaste.htm\n\nhttp://www.teenwire.com/ask/2004/as-20040209p735-smell.php
537614
ROFL!  Look around as if you're looking for where the horrendous odor could be coming from.  I'd tell you more, but just watch for me in the check out line.  You can learn my secrets there.\n\nOh come on people don't take it so seriously.  You flatulate too.  Maybe not in public, but you do it somewhere.
1023292
Fermented food produces different types of fumes, some of which smell. Flatulence contains odorless gases, such as nitrogen, carbon dioxide, oxygen, and methane, but it also contains the "oh-so-nasty" hydrogen sulfide, which causes the smell. If you have not noticed by now, some of the aforementioned fumes are flammable, like methane and oxygen, so you can, in fact, burn farts. Yes, you can set them aflame; it is not a myth, and a great way to impress the girls too... you do know I'm joking?\n\nHow much odor is produced also depends on the food you eat. Vegetarians might fart as often as meat-eaters, but their "serenades" do not smell as much because vegetables produce less hydrogen sulfide. The more sulfur rich the foods you eat, the more your farts will stink because bacteria will generate sulfides and mercaptans as they break down the nutrients. Beware: even though cauliflower is a vegetable, it also makes you stinky, so watch out!
1151586
A profound point. I think this is the reason: when you narrow the neck of a balloon when you let the air out, it makes a sort of farting sound. If the air inside this balloon smelled, it wouldn't smell as bad letting it out this way since only a little of it comes out at a time. However, if there's a huge opening in the balloon, all the air comes out at once, releasing all the smelly air into the world.
468212
I'm Indian and I'm offended by what you said. People of any race, creed, color, or nationality can have a stinky smell. It doesn't matter what race that person is. The cause for anyone would be a lack of hygeiene, not taking a shower, not brushing properly, not using mouthwash. If I wasn't such a nice guy, I would report you. Someone ought to though.
44686
Because it closer to the begining of the digestive journey.   When a fart comes out - it has had to go through the intestines and it picks up all the stinks that are in there!!  The gases get more noxious if you have a stomache ache too - for some reason it just rots in there and really wreaks everyone out when you pass it.
288458
you probably have some sort of fungus that produces the smell.  kill the fungus, stop the smell.
437289
The average human releases 0.5 to 1.5 litres (1 to 3 U.S. pints) of flatus a day by flatulating 12 to 25 times[1][2][3]. The primary constituents of flatulence are the non-odorous gases nitrogen (ingested), carbon dioxide (produced by aerobic microbes or ingested), and hydrogen (produced by some microbes and consumed by others), as well as lesser amounts of oxygen (ingested) and methane (produced by anaerobic microbes)[4]. Odors result from trace amounts of other components (often sulphur containing, see below).\n\nNitrogen is the primary gas released. Methane and hydrogen, lesser components, are flammable, and so flatulence is susceptible to catching fire. Not all humans produce flatus that contains methane. For example, in one study of the feces of nine adults, only five of the samples contained bacteria capable of producing methane[5]. Similar results are found in samples of gas obtained from within the rectum. The gas released during a flatus event frequently has a foul odor which mainly results from low molecular weight fatty acids such as butyric acid (rancid butter smell) and reduced sulfur compounds such as hydrogen sulfide (rotten egg smell) and carbonyl sulfide that are the result of protein breakdown. The incidence of odoriferous compounds in flatus increases from herbivores, such as cattle, to omnivores to carnivorous species, such as cats. Flatulence odor can also occur when there is a number of bacteria and/or feces in the anus while being expelled.
305121
The reason humans smell is because of the skin perispiration and it has also got a biological reason\n\nPerispiration is a process where skin respirates fresh oxygen and perispirates toxins and sweat which would cause sweat smell\n\nBut every Human bieng has a unique smell Biologiaclly Which is Different in Males and Females this is to attract the opposite sexes
207024
It depends on the permeation time of the smell (ie. dense gases spread faster in a closed environment than less condesed ones.)  Wind helps as well if it is an open environment.\n\nTo put it simply smell has too many variables to create a unified theory of odor permeation.\n\nBut I do know my farts seems to move fasters than other odors.
272151
The author of the question does not mean breathing as passing of gas, but flatus, to use its medical name, or to use the vulgar English term, farting.\n\nThe average human releases 0.5 to 1.5 litres (1 to 3 U.S. pints) of flatus in 12 to 25 episodes throughout the day. The primary constituents of flatulence are the non-odorous gases, in descending order of concentration, nitrogen (ingested), oxygen (ingested), methane (produced by anaerobic microbes), carbon dioxide (produced by aerobic microbes or ingested), and hydrogen (produced by some microbes and consumed by others). Odors result from trace amounts of other components (often sulphur containing, see below).\n\nNitrogen is the primary gas released. Methane and hydrogen, lesser components, are flammable, and so flatulence is susceptible to catching fire. Gas released mostly has a foul odor which mainly results from low molecular weight fatty acids such as butyric acid (rancid butter smell) and reduced sulfur compounds such as hydrogen sulfide (rotten egg smell) and carbonyl sulfide that are the result of protein breakdown. The incidence of odoriferous compounds in flatus increases from herbivores, such as cattle, to omnivores to carnivorous species, such as cats.\n\nI've lasted a good ten seconds letting one rip. Having had appendix problems for nine months (a long story, useless health system in the UK, etc.), I found that during that period, my flatus was more stinky than normal. Having had my appendix removed, it returned to normal in terms of odour.\n\nI find that drinking beer tends to produce the worst smelling flatus about twenty hours later.
946861
It's a reflex, a defence mechanism, in order to protect your lungs from taking in foul air for too long and polluting the air circulation system inside you! And then, also to protect your stomach from foul intake, as the smell induces puking and prevents you from eating the foul stuff! The Brain 'impressions' and the Mind reflexes together work towards safeguarding the Biology in you!
1163168
It depends, are you talking an alive person, or dead? If you're talking alive, then all we smell like is blood, kind of like iron and meat, except for the stomach, colon and bowels. They really aren't pleasant to smell. If you have an infection, that part of you will smell bad, it's really pretty nasty. \n\nIf you are talking dead, then yes, you stink. The smell comes from bacteria created to feed off your dead tissue, decomposition. That really smells horrible!! There is nothing worse then the smell of a decomposing body. As another person stated, when someone dies they will evacuate everything in their bowels and bladder. So that smell adds to the smell of decay. \n\nWhen I used to do medical research on bodies, the smell was horrible, but it's because of the chemicals they use to preserve the body. There were some days it took everything in me not to have to leave the room. I learned that the best way around it is a little bit of vikks vapor rub under your nose.. you don't smell anything after that, and it leaves your lip nice and tingly!!
132890
it shape, color, smell
583265
Simply because everthing around us can affect at least one of our 5 senses. Everything has a different taste, touch, smell, sound, look. If you can't see it then you probably can smell it. One way or another it can be detected---only exception I can think of would be carbon monoxide- odorless, unseen, cant hear it, touch it , or taste it. This is how we are protected from dangers and also how we enjoy things. If vomit did not smell like vomit (repulsive) then we would probably eat it as a dip for corn chips (ewww!) Usually nasty smells are meant to keep you away (safety) Another example -dog doo . If it smelled good we would collect it and rub some on our wrists so we would smell good. -could you imagine? Instead we avoid going near it- stepping in it etc...(although I'm usually the lucky one who finds the pile smd steps in it)\nFunny story- we were at Rockefeller Center two years ago at Christmas. While we were looking at the christmas tree I noticed a large whole in the crowd. When we got closer I swa that someone vomitted a whole yard's worth on the sidewalk(it looked like someone had a meal at an all-you can-eat-buffet there was so much. People were avoiding it like the plague. But one mommy and her stroller were too busy looking up to notice and she plowed right through it with her kid/stroller. Then she continued to step in it. No one could save her we just watched- SO GROSS \n A pretty elementary answer I know.