â€˜Odourâ€™ is undoubtedly the most complex problem of air pollution. Unfortunately, the only good measuring device for odour pollution is the human nose, which is notoriously undependable. Some individuals cannot detect odours easily whereas some have the ability to detect very minute
quantities of substances in the range of 1 ppb also. Moreover, people have a mixed reaction to a
given odour. Perfumes, very much liked by some people, may be very much disliked by others. There is a marked disagreement with reference to the offensiveness of selected odours. In addition, there are two other problems which interfere with the detection and measurement of odour. They are (i) unfamiliar odour is more easily detected and is more likely to cause complaints than a familiar one and (ii) because of odour fatigue, given sufficient time, a person may become accustomed to
almost any odour and be conscious of it only when a significant change in intensity occurs.
Food processing, oil refining, paper and rubber industries, tanneries, sugar mills, distilleries etc., are
the major odour emitting industries. Odours may not cause direct damage but are as much a nuisance
as noise, dust or corrosion. Until now, very little attention was given to the control of odorous air contaminants, consequently, Osmics, the science of smell, has remained unexplored to a great extent.