Human nose

If acetal resins are processed at temperatures substantially above those recommended for the particular grade, minor amounts of formaldehyde may be Hberated. Formaldehyde (qv) is a colorless, lacrimatory gas with a pungent odor and is intensely irritating to mucous membranes. The human nose is sensitive to concentrations in the range of 0.1 to 0.5 ppm. The current threshold limit value for formaldehyde is 1 ppm. 

As early as 1967, IFF chemists (11), in an in-depth study of jasmin absolute, identified an ultratrace amount of one of the key compounds in the entire fragrance repoitoire, hydroxycitroneUal [107-75-7] (21). This chemical has been used for many years in almost every "white flower" fragrance to give a very diffusive and lasting lily-of-the-valley and jasmin note, but this represents the only known identification of the compound in nature. This illustrates that the human nose can often predict the presence of a molecule well before the instmmentation becomes sufficiently sensitive to detect it. 

Quality Control. Reproducible production of perfumes requires careful quality control of all materials used as well as the compounding process itself. The use of analytical tools has iacreased over the years with their availability, but there can be no substitute for organoleptic evaluation. The human nose is far more sensitive than any analytical instmment for certain materials, yet it is also quite limited as a quantitative tool and is subject to fatigue. There are also weU-documented examples of specific anosmias ia iadividuals, ie, iaability to smell certain odor types, which is somewhat analogous to color-blindness. 

Gas treating is defined here as removal of H2S and CO2. Other sulfur compounds are discussed where applicable. Dehydration and sulfur production are not included, except for discussing sulfur production in the Stretford Process and for selective H2S removal. H2S must be removed from natural gas and process streams for health reasons and prevention of corrosion. Natural gas pipeline specifications require no more than % grain/100 SCF. This is equivalent to 4ppmv or 7ppmw (for a 0.65 specific gravity gas). By comparison, the human nose can detect... 

Organoleptic A material that influences a sensory organ, as in the perception of odor by the human nose. 

The human nose is often considered the best gas sensor, as the odor contained in the gas permits detection at levels as low as 190ppm or 0.01 per cent in air. Gas detectors are, however, sometimes used to give additional warnings of any leaks. The following points should be borne in mind when considering such an application ... 

Fortunately, such sophistication is not always necessary to compare containers. For example, a few days after the gas chromatography tests were completed, we opened the jars and were able to detect by sniffing that the grape odor from one container was noticeably more distinct than from the other. The methyl anthranilate, which had eluded the gas chromatograph, could be detected qualitatively and, for comparative purposes, quantitatively by the human nose. 

There are no data on the flux rates of leaf volatiles into the atmosphere. In the L. tridentata shrublands of North America and in areas in Australia where unpalatable, woody shrubs have replaced grasses, the presence of volatile hydrocarbons in the air is detectable by the human nose. The distinct odors of these hydrocarbons is especially noticeable after a rain. It has been suggested that these compounds may undergo atmospheric reactions that produce ozone and other oxidizing substances (8). However, there are no data on these atmospheric reactions. 

Bioassay of alternate molecular forms supports the view that the ORs are capable of resolving isomeric distinctions in neutral (non-biological) odourants. Stereochemical pairs of odours were tested for differential sensitivities in the blind subterranean mole rat (Spalax ehrenbergi). The subjects responded to one enantiomer, but not to its stereoisomer. Both sexes were attracted to the odour of R-(-)-carvone but unresponsive to S-(+)-carvone in contrast, males and females were repelled by the odour of (+)-citronellol, but not by (-)-citronellol (Heth et al., 1992). The lack of responsiveness by mole rats could be central due to lack of salience, or peripheral due to hyposmia/anosmia for one isomer. Both carvones have distinct odours for the human nose. 

The electronic nose is an example of an area in which the complexity of the analysis may make it difficult to replace a human with an ES. Electronic noses combine a sensor array with a neural network to make judgments about the composition of complex mixtures, such as fuels, wines, and natural oils. In such tasks, they often beat human noses in accuracy (Figure 7.8). 

Many sophisticated analytical techniques have been used to deal with these complex mixtures.5,45,46 A detailed description is not possible here, but it can be noted that GLC, often coupled with mass spectrometry (MS), is a major workhorse. Several other GLC detectors are available for use with sulfur compounds including flame photometer detector (FPD), sulfur chemiluminescence detector (SCD), and atomic emission detector (AED).47 Multidimensional GLC (MDGC) with SCD detection has been used48 as has HPLC.49 In some cases, sniffer ports are provided for the human nose on GLC equipment. 

Two different types of odor measurements can be performed, either analytical measurements or sensory measurements (cf. Section 7.1.4). Sensory measurements are either performed by the human nose or electronic detectors and, therefore, relate to the effects of the odor (Sneath and Clarkson, 2000 Stuetz et... 

Thioether. Mustard agent received its name because of garlic, horseradish, or mustard odor that can be detected by smell. The human nose can detect mustard (H, HD) in concentrations of 0.6 to 1.0 mg/m3. It must be understood that until recently, the U.S. military had no automatic vapor/liquid detection capability. Therefore, alert soldiers would most likely smell the agent vapor before encountering the liquid (after release, H or HD appears as a thick, colorless or pale yellow liquid HL, or mustard/lewisite mixture, appears as a dark oily cloud that can be detected visually). 

Landahl, H.D. and R.G.Herrmann. 1950. Retention of vapors and gases in the human nose and lung. Arch. Indust. Hyg. Occup. Med. 1 36-45. 

Consider that the odor perception by human nose is correlated with the odor value, OVj, in the headspace above the liquid. If a specific OVt distribution values is wanted, the perfume composition can be determined with the help of Equation (2). This methodology can facilitate the optimization of perfume compositions, reducing in this way some trial and error time and chemical wastes. Clearly, the problem is determined by structural decisions because the perfume composition depends on the interaction of the different perfume components. 

In contrast to the other large cats, the urine of the cheetah, A. jubatus, is practically odorless to the human nose. An analysis of the organic material from cheetah urine showed that diglycerides, triglycerides, and free sterols are possibly present in the urine and that it contains some of the C2-C8 fatty acids [95], while aldehydes and ketones that are prominent in tiger and leopard urine [96] are absent from cheetah urine. A recent study [97] of the chemical composition of the urine of cheetah in their natural habitat and in captivity has shown that volatile hydrocarbons, aldehydes, saturated and unsaturated cyclic and acyclic ketones, carboxylic acids and short-chain ethers are compound classes represented in minute quantities by more than one member in the urine of this animal. Traces of 2-acetylfuran, acetaldehyde diethyl acetal, ethyl acetate, dimethyl sulfone, formanilide, and larger quantities of urea and elemental sulfur were also present in the urine of this animal. Sulfur was found in all the urine samples collected from male cheetah in captivity in South Africa and from wild cheetah in Namibia. Only one organosulfur compound, dimethyl disulfide, is present in the urine at such a low concentration that it is not detectable by humans [97]. 

The question of distance is important legally in deciding whether to specify distances between odour sources and housing, hospitals, schools etc. The rules operated in Germany, the Netherlands and Australia are of great interest and it may be significant that Australia, which has much more space and lower concentrations of humans than Europe, allows larger distances between source and human nose than does Europe. 

Olfactometers are physical instruments which use the human nose as a sensor. As a consequence, the possibilities and limitations of the instrument are determined to a large extent by the properties of the human subject. In this paper we will describe these properties and we will indicate which steps should be taken to optimize the use of the human subjects involved in olfactometric measurements. Such recommendations will be concerned with ... 

Since the human nose adapts to odours to such an extent that after a short while in an... 

As we are regarding odoriferous pollutants, the immisson is their entrance into a human nose. 

Observations of smoke plumes, first brief tests and some papers 15, 6/ suggest that the immission concentration is fluctuating in a wide range near the source. Human nose is more sensitive to odour concentration fluctuation than, due to adaption, to constant odour concentration. In fig. 5 it is shown qualitativly that odour perception may occur due to concentration fluctuations although the mean value is far below the odour threshold. In table 1 it is indicated that the distance between agricultural emission sources and receptor is relatively small in relationship to industrial emissions. 

Despite the technical advances in the past decade, no apparatus for measurement of the odour strength has been developed. Therefore, odour pollution studies cannot be performed without using human noses. In general, the efect of polluting odours can be studied either by direct assessment in the ambient air or by means of a dispersion calculation. The first method requires a number of observers to be placed in the vincinity of the odour source (3,7). The latter a dispersion model and an input value. For reasons of simplicity this method is most frequently used in the Netherlands. 

Odour quality depends not only on the sensitivity of the human nose but also on the subjectivity of the human language to be able to describe the odour (17). Some chemical characteristics of slurry have been compared to the slurry odour. A relationship between volatile fatty acids (VFA) and odour offensiveness of poultry manure was described by... 

It was the first device of its kind and appeared to have great potential. Physicians had long noted, for example, that distinctive odors are associated with some diseases. Since the people sniffed greatly surpassed the human nose in sensitivity, it might pick up serious progressive illnesses at earlier stages, enabling timely treatment. 

---