Odor - The Electronic Nose Artificial Olfaction Technology - page 87

These cells are surrounded by supporting cells. At the base of the epithelium are
basal cells. Bundles of axons of the olfactory receptor cells pass through the
foramina of the cribriform plate of the ethmoid bone and then synapse with
neurons of the olfactory bulbs of cranial nerve I.
The actual breath contains mixtures of oxygen, carbon dioxide, water vapor,
nitrogen, inert gases, in addition may also contain various elements and more than
1,000 trace volatile compounds. Concentrations ranges are from ppm to ppt. The
Volatile Organic Compounds (VOCs) commonly found in normal breath are
acetone, ethane, and isoprene which are nothing but the metabolic products [ 5 ].
Approximately a thousand different kinds of olfactory receptors are there in
human nose, and it is thought that each can sense a single kind of chemical bond in a
molecule.

4.4 Types of Odor

Seven primary odorant classes are listed in Table 4.1

4.4.1 Characteristics of Odor

• Substances of similar or dissimilar chemical constitution may have similar odor.
Nature and strength of odor may change on dilution.
• Weak odor is not perceived in presence of strong odor.
• Odor of same strength blends to produce a combination in which one or both
may be unrecognizable.
• Constant intensity of odor causes an individual to quickly loose awareness of the
sensation and only noticed when it varies in intensity.
• Fatigue for one odor may not affect the perception of dissimilar odor but will
interfere with the perception of similar odor.
• An unfamiliar odor is more likely to cause complaint than a familiar one.
• Two or more odorous substances may cancel the smell of each other.
• Odor travels downwind.

Table 4.1 Primary odorant

Odor Example

Camphoric Mothballs

Musky Perfume/Aftershave

Roses Floral

Peppermint Mint gum

Ethereal Dry cleaning fluid

Pungent Vinegar

Putrid Rotten Eggs