Odor
 |
Odor receptors on the antennae of a Luna moth |
An
odor or
odour (see
spelling differences) is the object of perception of the
sense of
olfaction. Odors are also called
smells. The term
stench or
pong is used to describe an unpleasant odor. The term
fragrance or
aroma is used primarily by the
food and cosmetic industry to describe a pleasant odor, and is sometimes used to refer to
perfumes. Odors correspond to the objective phenomenon of chemicals dissolved in air, although, as with other senses, psychological factors can play a part in perception.
Some odors such as perfumes and flowers, are much sought after and large prices are paid for the most elite ones. Other whole industries have developed products to remove unpleasant odors. See
deodorant. The perception of odors is also very much dependent upon circumstance. The odor of
cooking processes may be agreeable while cooking, but not after the
meal when one is full. It is also culturally dependent.
The odour molecules send messages to the Limbic system , the area of the brain that governs emotional responses. These messages have the power to alter moods, evoke distant memories , raise our spirits & boost self confidence. Consequently, Fragrances positively affect sleep , stress , alertness , social interaction and general feelings of well being. Fragrance has thus been recognised as a tool for rebalancing the mind and the body. This recognition has lead to the concept of "Aromatherapy" wherein fragrances are administered in appropriate dosages to cure problems related to the human psychology.
The study of olfactory odors is a growing field, but is a complex and difficult one. The human
olfactory system can detect many thousands of scents based on only very minute airborne concentrations of a chemical. The sense of smell of many animals is even better. Some fragrant flowers give off
odor plumes that move downwind, and are detectable by
bees more than a kilometer away.
Pheromones are odors that are deliberately used for communication. A female
moth may release a pheromone that can entice a male moth that is several kilometers away.
Honeybee queens constantly release pheromones that regulate the activity of the
hive. Workers can release such odors to call other bees into an appropriate cavity when a swarm moves in, or to "sound" an alarm when the hive is threatened.
There are hopes that advanced smelling machines could do everything from test perfumes to help detect cancer or explosives by detecting certain scents, but as of yet artificial noses are still problematic. The complex nature of the human nose, its ability to detect even the most subtle of scents, is at the present moment difficult to replicate.
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 statisically 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.
*
Olfaction*
Machine olfaction*
Odors categorized by main chemical constituent and organized by odor class, percept, etc.*
Odors can be quantified for applications in industry such as a manufacturer wanting to control emissions to reduce complaints from neigbors and to conform with governmental environmental regulations
