quote:Old info. The gases reponsible for the odor are hydrogen sulfide, dimethyl sulfoxide and methanet
I already said that in the 2nd link I mentioned there is some controversy about the source of odor. The 2nd link is
http://www.hypertension-consult.com/Secure...re_Book/107.htm The info from the second link."Malodorous FlatusDespite the enormous amount of discussion devoted to the topic of flatus odor, there has been minimal study of the factors responsible for this odor.3 It was taught for many years that the offensive odor of flatus resulted from its content of aromatic breakdown products of proteins such as indole and skatole. However, Moore et al, in an elegant study of human feces, concluded that these aromatic compounds were present in very low concentration and that these compounds had an odor distinctly different from human feces.37 These workers concluded that three sulfur-containing gases�methanethiol, dimethyldisulfide, and trimethylsulfide�were the major offensive gases elaborated by human feces.We recently carried out the first systematic study designed to identify the odoriferous components of human flatus.3 In this study, 87 individual flatus passages obtained from healthy subjects were collected via rectal tube and analyzed for sulfur containing gases. In contrast to the findings of Moore et al with human feces, we found the predominant sulfur gases in flatus to be H2S, methanethiol, and dimethylsulfide (please see Figure 3), with H2S being the predominant gas. The discrepancy between our findings and those of Moore et al appears to reflect the fact that the compounds we observed in flatus are all highly volatile and thus would rapidly leave the feces for the gas space. In contrast, two of the compounds observed by Moore and co-workers in feces, dimethyldisulfide and trimethylsulfide, have very low volatility. Thus, it is not surprising that these compounds are found in feces but not the surrounding gas phase (i.e., flatus).While sulfur-containing gases are present in very low concentrations (< 0.01%) in flatus, these compounds have a very powerful, offensive odor. To actually determine if these gases were responsible for flatus malodor, it was necessary to employ the only instrument capable of judging the offensiveness of an odor�the human nose. In what is known as the �sniff test,�38 two judges, previously shown to have excellent olfactory discrimination, blindly ejected a small amount of flatus contained in a syringe at a distance of about 5 cm from the nose. The offensiveness of the odor was rated on a linear scale. As shown in Table 2, a highly significant correlation was observed between the intensity of malodor and the concentrations of the sulfur gases. Such a correlation could indicate that the gases were associated with the presence of other odoriferous compounds as opposed to being cause of the odor. Thus, further experiments were carried out in which flatus samples were treated with zinc, which avidly binds the sulfhydryl components of H2S and methanethiol. This treatment markedly reduced the odor, indicating that the two sulfur-containing gases were very likely responsible for much of the offensive smell of flatus. Lastly, artificial flatus samples comprised of the three sulfur containing gases in concentrations typical of flatus were blindly presented to our judges. These mixture were rated to be offensive and to have a fecal-like odor.Table 2. Correlation Between the Concentration of Sulfur-Containing Gases and Odor Intensity of Flatus Passages* On the basis of the above evidence, we concluded that the sulfur gases were the predominant,
but probably not the only offensive malodorous component of flatus. This knowledge simplifies studies of flatus odor in that the objective measurement of the concentration of gases can be employed in place of the time-consuming subjective evaluation of odor."flux we often have gas which does not smell like sulphur or feaces. For example the skunk like smell is from marcaptans. And then there is the sewer like smell too and doezens of others that I can't name.
