What is The Process of Olfaction – Odor Perception ?

What is The Process of Olfaction – Odor Perception ?


The sense of olfaction is complex. Odor perception is influenced by many factors unique to each individual as well as external environmental factors. The basis of odor perception is the contact between chemical molecules, mainly in the gaseous state, which can be detected by the olfactory epithelium.


From : Pour la science # 218

The odorous molecules come into contact with the olfactory epithelium at the top of the nasal cavity and stimulate multiple chemically cell receptors (see figures).


From : Pour la science # 218

The electrical impulses generated by the olfactory epithelium cells are transmitted via the olfactory nerve (first cranial nerve which passes through the skull through the cribriform plate) in the central olfactory system located in the limbic system. A branch of the fifth cranial nerve, the trigeminal, is the vehicle for the perception of irritation at the nose, the nasopharynx and the oropharynx, as well as the sensation of taste and smell.


From: LAFFORT P., Aspects of the olfactory information, chap 6 dans Characterization and control of odours and VOC in the process industries, VIGNERON S., HERMIA J., and CHAOUKI J. Eds, Studies in Environmental Science, 61, Amsterdam, The Netherlands, 1994.

The trigeminal nerve also contributes to assess the odor perception magnitude even without irritation. It is interesting to note that some molecules are detected as well by irritation as by olfaction: ammonia, NOx, Ozone, ect.

The perception of an odor by humans results from a stimulus. It includes key information as the odor intensity and odor quality. Our ability to collect this information makes the olfaction a very complex sense.  All the biochemical parameters are not yet fully understood by specialists.

For the intensity, our sense of smell behaves much like our perception of hot or cold substances. The signal strength is very strong at the beginning then there is adaptation and gradual decline in signal strength (toe in a bath). In terms of odor quality, our sense of smell works similarly to taste: we can recognize, classify and assess the quality of an odor.

One of the quality of olfactometry is that a lot of the odor perception complexity is tied in a reproducible quantified parameter: the odor concentration.


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Thierry Page
Thierry Page
Thierry Pagé, Founder & Senior Odor Expert, Odotech. Industry Leader in Odor Monitoring & Odor Management. Invented OdoWatch and revolutionized odor monitoring state of the art. He is passionate to serve the industry from WasteWater, Residuals & Waste, Mining, Agri-Food, Manufacturing and Petrochemistry. Participated in projects in more than 20 countries.