Sense of smell

It quickly deadens the sense of smell. Sulfur dioxide is a dangerous component in atmospheric air pollution. 

Human perception creates difficulty ia the characterization of flavor people often, if not always, perceive flavors differently due to both psychological and physiological factors. For example, certain aryl thiocarbamates, eg, phenylthiocarbamide, taste exceedingly bitter to some people and are almost tasteless to others (5). This difference is genetically determined, and the frequency of its occurrence differs from one population to another 40% of U.S. Caucasians are nontasters, whereas only 3% of the Korean population caimot perceive the strong bitter taste of the aryl thiocarbamates (6). Similar differences were found ia the sense of smell for compounds such as menthol, carvone, and ethyl butyrate (7). 

Whatever the physiology of odor perception may be, the sense of smell is keener than that of taste (22). If flavors are classed into odors and tastes as is common practice in science, it can be calculated that there are probably more than 10 possible sensations of odor and only a few, perhaps five, sensations of taste (13,21,35—37). Just as a hereditary or genetic factor may cause taste variations between individuals toward phenylthiourea, a similar factor may be in operation with odor. The odor of the steroid androsterone, found in many foods and human sweat, may eflcit different responses from different individuals. Some are very sensitive to it and find it unpleasant. To others, who are less sensitive to it, it has a musk or sandalwood-like smell. Approximately 50% of the adults tested cannot detect any odor even at extremely high concentrations. It is befleved that this abiUty is genetically determined (38). 

Jiutosmia. Disorder of the sense of smell in which odors are perceived when none are present. 

Microsmatic. Having a poorly developed sense of smell. 

Parosmia. A disturbance to the sense of smell resulting ia smelling the wrong odors, usually perceived as repulsive. 

The vomeronasal organ (VNO), located in the nose, is a small chemical sensing stmcture associated with odors and behavioral effects. The vomeronasal system, which is made up of the VNO and a portion of the brain s limbic system, is stmcturaHy independent of the olfactory and nervous terminalis systems in the nose. It may, however, interact with these systems in a manner dependent on prior experience or learning, and therefore be direcdy related to the association of smells and experiences. This independent chemosensory system in the nose may prove to open doors to new learning associated with the sense of smell and human behavior. 

In 1986, the National Geographic Society, in cooperation with the MoneU Center, conducted a worldwide survey of the sense of smell. Over 10 million survey forms were sent to readers of the Society s journal, of which close to 1.5 million forms were completed and returned. With responses to 40 demographic and 42 odor-related questions, the results constitute the largest set of data on human olfaction (4). 

The sense of smell is rapidly fatigued. Fatigue for one odor does not affect the perception of other dissimUar odors, but wUl interfere with the perception of similar odors. Two or more odorous substances may cancel each other out this compensation means that two odorous substances smelled together may be inodorous. 

Odors play a much greater role in human behavior than previously thought. The sense of smell provides a direct link with the function of the brain therefore, the further study of olfaction can only advance the learning of causes and effects of stimuli to the brain. 

Cross-country gas pipelines generally must odorize the normally odorless, colorless, and tasteless gas ia urban and suburban areas, as is required of gas distribution companies. Organosulfur compounds, such as mercaptans, are usually used for this purpose, and code requires that the odor must be strong enough for someone with a normal sense of smell to detect a gas leak iato air at one-fifth the lower explosive limit of gas—air mixtures. The latter is about 5%, so the odorant concentration should be about 1%, but most companies odorize more heavily than this as a safety precaution. 

The odor threshold of carbon disulfide is about 1 ppm in air but varies widely depending on individual sensitivity and purity of the carbon disulfide. However, using the sense of smell to detect excessive concentrations of carbon disulfide is unreHable because of the frequent co-presence of hydrogen sulfide that dulls the olfactory sense. 

Some materials with low odour duesholds may paralyse die olfactory nerves and cause the sense of smell to be lost within minutes (e.g. hydrogen sulphide). 

Workers may become acclimatized to a commonly-occuiTing odour, or be suffering temporarily from an impaired sense of smell, e.g. due to a cold. 

Do not rely on the sense of smell to deteet hydrogen sulphide leaks. Strips of wet lead aeetate paper turn blaek on exposure to hydrogen sulphide and offer a simple indieator, as do eolour indieator tubes. For plant-seale operations, instrumental multi-point deteetors and alarms are likely to be more appropriate. 

Hydrogen sulfide gas Hydrogen sulfide is a gas with a rotten egg odor. This gas is produced under anaerobic conditions. Hydrogen sulfide is particularly dangerous because it dulls your sense of smell so that you don t notice it after you have been around it for a while and because the odor is not noticeable in high concentrations. The gas is very poisonous to your respiratory system, explosive, flammable, and colorless. 

Odor Relating to the sense of smell, a substance that stimulates the olfactory organ, allowing us to detect if a smell is pleasant or unpleasant. 

At 0.13 ppm by volume, H2S can be sensed by smell. At 4.6 ppm the smell is quite noticeable. As the concentration increases beyond 200 ppm, the sense of smell fatigues, and the gas can no longer be detected by odor. Thus, H2S cannot always be detected by smell. Even if H2S cannot be smelled, it is possible that there is sufficient H2S present to be life threat-... 

Coughing, eye irritj sense of smell after minutes. Altered re i s, and drowsi. t 3u minutes, followed by throat irritation after one hour. 1 exposine results in a grai increase in the severity o symptoms. 

Kills sense of smell rapidly, bums eyes and throat. 

The fact that the hygrometric state of the air influences the sense of smell is probably more validly explained by the fact that moist air is capable of carrjdng a larger proportion of tbe vapour of a volatile substance than is dry air. 

Elemental bromine is a readily evaporating liquid (pBr at 1 °C = 0.23 bar) with high reactivity. Because of the good solubility of Br2 in lipids, its aggressive and toxic properties affect skin and mucous membranes (bronchi). The MAK value of elemental Br2 is defined as 0.1 ppm (0.7 mg m 3), while the sense of smell is affected at a value of 0.01 ppm. The lethal concentration (around 100-200 ppm) is reached for example, by twice the MAK value, 5 min, eight times per working unit [91, 92]. 

---