![Passiflora foetida is a species of passion flower that is native to the southwestern United States (southern Texas and Arizona), Mexico, the Caribbean, Central America, and much of South America. It has been introduced to tropical regions around the world,[1] such as Southeast Asia and Hawaii. Common names include wild water lemon, stinking passion fruit, and running pop.[1][2] It is a creeping vine like other members of the genus, and yields an edible fruit.[3] The specific name, foetida, means](http://web.archive.org./web/20110808061944im_/http://cdn.wn.com/pd/29/f1/f01d2307407ac6d74c1fd88add76_grande.jpg "Passiflora foetida is a species of passion flower that is native to the southwestern United States (southern Texas and Arizona), Mexico, the Caribbean, Central America, and much of South America. It has been introduced to tropical regions around the world,[1] such as Southeast Asia and Hawaii. Common names include wild water lemon, stinking passion fruit, and running pop.[1][2] It is a creeping vine like other members of the genus, and yields an edible fruit.[3] The specific name, foetida, means")
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An odor or odour is caused by one or more volatilized chemical compounds, generally at a very low concentration, that humans or other animals perceive by the sense of olfaction. Odors are also called scents, which can refer to both pleasant and unpleasant odors. The terms fragrance, scent, and aroma are used primarily by the food and cosmetic industry to describe a pleasant odor, and are sometimes used to refer to perfumes. In contrast, malodor, stench, reek, and stink are used specifically to describe unpleasant odors.
The widest range of odors consists of organic compounds, although some inorganic substances, such as hydrogen sulfide and ammonia, are also odorants. The perception of an odor effect is a two-step process. First, there is the physiological part; the detection of stimuli by receptors in the nose. The stimuli are processed by the region of the human brain which is responsible for olfaction. Because of this, an objective and analytical measure of odor is impossible. While odor feelings are very personal perceptions, individual reactions are related to gender, age, state of health, and private affectations. Common odors that people are used to, such as their own body odor, are less noticeable to individuals than external or uncommon odors. This is due to habituation, after continuous odor exposure the sense of smell fatigues quickly, but recovers rapidly. Odors can change due to environmental conditions, for example odors tend to be more distinguishable in cool dry air.
Habituation is the the ability to generalize odors after continuous exposure. The sensitivity and ability to discriminate odors diminishes with exposure to ignore continuous stimulus and focus on a particular sense. When odorants are mixed, the conditioned odorant is blocked out because of habituation. This depends on the strength of the odorants in the mixture which can change perception and processing of an odor. This process helps classify similar odors as well as adjust sensitivity to differences in complex stimuli.
For most people, the process of smelling gives little information concerning the ingredients of a substance. It only offers information related to the emotional impact. Experienced people, however, such as flavorists and perfumers, can pick out individual chemicals in complex mixes through smell alone.
Odor perception is a primal sense. Sense of smell enables both pleasure, can non consciously warn animals of danger, help locate mates, find food, or detect predators. Humans have a surprisingly good sense of smell even though they only have 350 functional olfactory receptor genes compared to the 1,300 found in mice correlated to an evolutionary decline in sense of smell. Humans remarkable sense of smell is just as good as most animals and can distinguish a diversity of odors- approximately 10,000 scents. This is because of the retro nasal route in humans to increase sensation. However, animals such as dogs show a greater sensitivity to odors than humans especially in studies using short chained compounds. Higher cognitive brain mechanisms and more olfactory brain regions enable humans to discriminate odors better than other mammals despite less olfactory receptor genes. It has been proposed that there are seven primary odors: ( with examples) 1.) musky- perfumes/aftershave 2.) putrid- rotten eggs 3.) pungent- vinegar 4.) camphoraceous- mothballs 5.) ethereal- dry cleaning fluid 6.) floral- roses 7.) pepperminty- mint gum
In Germany, the concentrations of odorants have since the 1870s been defined by the “Olfaktometrie”, which helps to analyze the human sense of smell using the following parameters: odor substance concentration, intensity of odor, and hedonic assessment.
To establish the odor concentration, an olfactometer is used which employs a panel of human noses as sensors. In the olfactometry testing procedure, a diluted odorous mixture and an odor-free gas (as a reference) are presented separately from sniffing ports to a group of panelists, which are housed in an odor neutral room. They are asked to compare the gases emitted from each sniffing port, after which the panelists are asked to report the presence of odor together with a confidence level such as guessing, inkling, or certainty of their assessment. The gas-diluting ratio is then decreased by a factor of two (i.e. chemical concentration is increased by a factor of two). The panelists are asked to repeat their judgment. This continues for a number of dilution levels. The responses of the panelists over a range of dilution settings are used to calculate the concentration of the odor in terms of European Odor Units (ouE/m³). The main panel calibration gas used is Butan-1-ol., which at a certain diluting gives 1 ouE/m³.
It has been proposed that there are seven primary odors: ( with examples) 1.) musky- perfumes/aftershave 2.) putrid- rotten eggs 3.) pungent- vinegar 4.) camphoraceous- mothballs 5.) ethereal- dry cleaning fluid 6.) floral- roses 7.) pepperminty- mint gum
When measuring odor, there is a difference between and measurements. Emission measurement can be conducted by olfactometry using an olfactometer to dilute the odor sample. On the contrary, olfactometry is rarely used for immission measurement because of the low odor concentrations. The same measuring principals are used, but the judgment of the air assay happens without diluting the samples.
Initial entry into a room provides the most accurate sensing of smell.
Sensation of odor has 4 properties related to threshold and tolerance: Odor concentration, odor intensity, odor quality, and hedonic tone
The measurement of odor concentration is the most widespread method to quantify odors. It is standardized in CEN EN 13725:2003. The method is based on dilution of an odor sample to the odor threshold (the point at which the odor is only just detectable to 50 % of the test panel). The numerical value of the odor concentration is equal to the dilution factor that is necessary to reach the odor threshold. Its unit is the European Odor Unit, OUE. Therefore, the odor concentration at the odor threshold is 1 OUE by definition.
To establish the odor concentration, an olfactometer is used which employs a group of panelists. A diluted odorous mixture and an odor-free gas (as a reference) are presented from sniffing ports to a group of panelists. In comparing the odor emitted from each port, the panelists are asked to report if they can detect a difference between the ports. The gas-diluting ratio is then decreased by a factor of 1.4 or two (i.e. the concentration is increased accordingly). The panelists are asked to repeat their judgment. This continues until the panelists respond certain and correct twice in a row. These responses used to calculate the concentration of the odor in terms of European Odor Units (OUE/m3).
The test persons must fulfill certain requirements, for example regarding their sensitivity of odor perception. The main panel calibration gas to verify this requirement used is n-Butanol (as 1 OUE/m3≡40 ppb/v n-butanol).
To collect an odor sample, the samples must be collected using specialized sample bags, which are made from an odor free material e.g. Teflon. The most accepted technique for collecting odor samples is the lung technique, where the sample bag is placed in a sealed drum, and a vacuum is placed on the drum, which fills the sample bag as the bag expands, and draws the sample from the source into the bag. Critically, all components which touch the odor sample, must be odor free, which includes sample lines and fittings.
A human's odor detection threshold is variable. Repeated exposure to an odorant leads to enhanced olfactory sensitivity and decreased detection thresholds for a number of different odorants. It was found in a study that humans that were completely unable to detect the odor of androstenone developed the ability to detect it after repeated exposure.
Humans can discriminate between two odorants that differ in concentration by as little as 7%.
There are a number of issues which have to be overcome with sampling, these include: - If the source is under vacuum - if the source is at a high temperature - If the source has high humidity
Issues such as temperature and humidity are best overcome using either pre-dilution or dynamic dilution techniques.
Perceived strength of the odor sensation is measured in conjunction with odor concentration. This can be modeled by the Weber-Fechner law: I= a * log(c)+b
I is the perceived psychological intensity at the dilution step on the butanol scale, a is the Weber-Fechner coefficient, C is the chemical concentrations, and b is the intercept constant (0.5 by definition)
These are a function of modelled concentration, averaging time (over what time period the model steps are run over (typically hourly)) and a percentile. Percentiles refer to a statistical representation of how many hours per year, the concentration C may be exceeded based on the averaging period.
Indirect refers to collecting samples from the air stream which has already passed over the emitting surface.
The most commonly used direct methods include the Flux Chamber and wind tunnels which include the UNSW Wind tunnel. There are many other available techniques, and consideration should be given to a number of factors before selecting a suitable method.
A source which has implications for this method are sources such as bark bed biofilters, which have a vertical velocity component. For such sources, consideration needs to be given as to the most appropriate method. A commonly used technique is to measure the odor concentration at the emitting surface, and combine this with the volumetric flow rate of air entering the biofilter to produce an emission rate.
Many methods are used, but all make use of the same inputs which include - Surface roughness - Upwind and down wind concentrations - Stability class (or other similar factor) - Wind speed and direction
While developing environmental legislation in Germany, it was noted that there was a need for a method with which to accurately measure odor. Since that time, the following laws have been made:
#“refinery guideline” (early 1970s) #federal emission protection law (1974) #technical guideline to keep the air fresh #olfactory emission guideline (early 1980s until 1998)
Controls at the point of the emission, like plural vitrification against aircraft noise, drop out. Terms of transmission could be marginally changed by establishing ramparts, plantings and so on, but the objective efficiency of those controls is likely minimal. But the subjective efficiency of a plantings is remarkable.
The choice of the location is the most important control. This involves keeping an adequate distance from the nearest receptor and paying attention to the meteorological conditions; e.g., prevailing wind direction. Reducing the concentraion of an odor (emission), by diluting a small emission with a large air flow, could be an effective and economic alternative to reducing the emission with different controls. Encapsulating of olfactory relevant asset areas is the best known method to reduce the emission, but it is not the most suitable one. Different matters need to be considered by encapsulation. Within an enclosure a damp and oppressive atmosphere can arise, so that the inner materials of the capsule produce a high degree of mechanical stress. Not to let the explosion hazard slide.
For encapsulation to be viable, there must be some way to exhaust the spent air. When emission is avoided through capsuling, odorants remain inside the medium and tend to leak at the next suitable spot. In any case, capsuling is never really gas-proof, and at some spots substances may leak out at considerably higher concentrations.
There are three different ways exhausted air may be treated:
Physisorption is an exothermic and reversible reaction. Obviously stronger strengths accrue through the interaction between solid dipoles at polar surfaces or reflexive loadings, appearing in electric conductive surfaces. Such interactions could be defined as a chemisorption because of their strength.
In many reactions, physisorption is a pre-cursor to chemisorption. Compared to physisorption, chemisorption is not reversible and requires a larger activation energy. Usually the bond energy is about 800 kJ/mol. For physisorption the bond energy is only about 80 kJ/mol. A monomolecular layer could be maximally adsorbed. Strong bonds between the adsorbative molecules and the substrate could lead to the point that their intermolecular bonds partly or completely detach. In such a case you have to call this a dissociation. Those molecules are in a highly reactive state. This is the basis of heterogeneous catalysis. The substrate is then called catalytic converter. The differences between Chemisorption and Physisorption extends beyond an increased activation energy. An important criteria for chemisorption is the chemical mutation of the absorbent. Thereby it is possible that you have to deal with a chemisorption in a few combinations with a relatively low bond energy, for example 80 kJ/mol, as a physisorption could be another combination with a bond energy even by 100 kJ/mol. The interaction with different adsorbative molecules is very different. The surface could be taken by substances, which point out a very high bond energy with the substrate, and as a consequence of this the wanted reaction is impossible. Because of that feature those substances are called catalytic converter venom. Heat is released during that process too.
The odor molecules transmit messages to the limbic system, the area of the brain that governs emotional responses. Some believe that these messages have the power to alter moods, evoke distant memories, raise their spirits, and boost self-confidence. This belief has led to the concept of “aromatherapy” wherein fragrances are claimed to cure a wide range of psychological and physical problems. Aromatherapy claims fragrances can positively affect sleep, stress, alertness, social interaction, and general feelings of well-being. However, the evidence for the effectiveness of aromatherapy consists mostly of anecdotes and lacks controlled scientific studies to back up its claims.
With some fragrances, such as those found in perfume, scented shampoo, scented deodorant, or similar products, people can be allergic to the ingredients. The reaction, as with other chemical allergies, can be anywhere from a slight headache to anaphylactic shock, which can result in death.
Unpleasant odors can arise from specific industrial processes, adversely affecting workers and even residents downwind of the industry. The most common sources of industrial odor arise from sewage treatment plants, refineries, specific animal rendering plants and industries processing chemicals (such as sulfur) which have odorous characteristics. Sometimes industrial odor sources are the subject of community controversy and scientific analysis.
The study of odors can also get complicated because of the complex chemistry taking place at the moment of a smell sensation. For example iron metal objects are perceived to have an odor when touched although iron vapor pressure is negligible. According to a 2006 study this smell is the result of aldehydes (for example nonanal) and ketones (example: 1-octen-3-one) released from the human skin on contact with ferrous ions that are formed in the sweat-mediated corrosion of iron. The same chemicals are also associated with the smell of blood as ferrous iron in blood on skin produces the same reaction.
Most artificial or electronic nose instruments work by combining output from an array of non-specific chemical sensors to produce a finger print of whatever volatile chemicals it is exposed to. Most electronic noses need to be "trained" to recognize whatever chemicals are of interest for the application in question before it can be used. The training involves exposure to chemicals with the response being recorded and statistically analyzed, often using multivariate analysis and neural network techniques, to "learn" the chemicals. Many current electronic nose instruments suffer from problems with reproducibility with varying ambient temperature and humidity. An example of this type of technology is the colorimetric sensor array, which visualizes odor through color change and creates a picture of it.
Human body odors influence interpersonal relationships. Human body odors are involved in adaptive behaviors, such as parental attachment in infants or partner choice in adults."Mothers can discriminate the odor of their own child, and infants recognize and prefer the body odor of their mother over that of another woman. This maternal odor appears to guide infants toward the breast and to have a calming effect" Body odor is involved in the development of infant–mother attachment and is essential to a child’s social and emotional development bringing feelings of security. Reassurance created by familiar parental body odors may contribute significantly to the attachment process.
How a man smells is critical for woman to find a lover. Body odor is a sensory cue critical for mate selection because it is a signal of immunological health. Women prefer men with major histocompatibility complex (MHC) genotypes and odor different then themselves especially during ovulation. Different MHC alleles are favorable because different allele combination's would maximize disease protection and minimize recessive mutations in offspring. Biologically females tend to select mates "who are most likely to secure offspring survival and thus increase the likelihood that her genetic contribution will be reproductively viable."
Studies have suggested that people might be using odor cues associated with the immune system to select mates. Using a brain imaging technique, Swedish researchers have shown that gay and straight males' brains respond differently to two odors that may be involved in sexual arousal, and that the gay men respond in the same way as straight women, though it could not be determined whether this was cause or effect. The study was expanded to include lesbian women; the results were consistent with previous findings meaning that lesbian women were not as responsive to male identified odors, while their response to female cues was similar to straight males. According to the researchers, this research suggests a possible role for human pheromones in the biological basis of sexual orientation.
An odor can cue a memory. Most memories that pertain to odor come from the first decade of life compared to verbal and photo memories which usually come from 10-30 years of life.Odor-evoked memories are more emotional, associated with stronger feelings of being brought back in time, and have been thought of less often as compared to memories evoked by other cues.
The new car smell is not intentional by the manufacturer but is the smell “of number of harmful chemicals, including antimony, bromine, chlorine, and lead. Repeated and concentrated exposure to any of these chemicals may contribute to a variety of acute and long-term health issues such as birth defects, impaired learning, liver toxicity, and cancer.”
Currently there is no regulation of the use of scent in product design. The FDA has no say as to what items are used to create a scent. If ingredients are listed on a product, the term fragrance can be used in a general sense. The National Academy of Sciences (NAS) reports that “95 percent of the ingredients used to create fragrances today are synthetic compounds derived from petroleum, including benzene derivatives, aldehydes, and many other known toxins and sensitizers. Many of these substances have been linked to cancer, birth defects, central nervous system disorders, and allergic reactions.”
This text is licensed under the Creative Commons CC-BY-SA License. This text was originally published on Wikipedia and was developed by the Wikipedia community.
![Passiflora foetida is a species of passion flower that is native to the southwestern United States (southern Texas and Arizona), Mexico, the Caribbean, Central America, and much of South America. It has been introduced to tropical regions around the world,[1] such as Southeast Asia and Hawaii. Common names include wild water lemon, stinking passion fruit, and running pop.[1][2] It is a creeping vine like other members of the genus, and yields an edible fruit.[3] The specific name, foetida, means](http://web.archive.org./web/20110808061944im_/http://cdn.wn.com/pd/29/f1/f01d2307407ac6d74c1fd88add76_thumb.jpg "Passiflora foetida is a species of passion flower that is native to the southwestern United States (southern Texas and Arizona), Mexico, the Caribbean, Central America, and much of South America. It has been introduced to tropical regions around the world,[1] such as Southeast Asia and Hawaii. Common names include wild water lemon, stinking passion fruit, and running pop.[1][2] It is a creeping vine like other members of the genus, and yields an edible fruit.[3] The specific name, foetida, means")
