Odour Threshold Investigation 2012 - Bay of Plenty Regional Council

Figure 2.1 Odorant receptors and the organisation of the olfactometry system 8 .
How an odour is perceived and its subsequent effects are not straightforward. The
human perception of odour is governed by complex relationships, and its properties
need to be considered when assessing potential odour effects.
2.3 Human sensitivity to odours
Our response to odours follows certain characteristic patterns common among most
human sensory systems. For example, olfactory acuity in the population conforms to
a normal distribution. Most people, assumed to be about 96% of the population,
have a “normal” sense of smell as depicted in Figure 2.2. Two percent of the
population are predictably hypersensitive and two percent insensitive. The
insensitive range includes people who are anosmic (unable to smell) and hyposmic
(partial smell loss). The sensitive range includes people who are hyperosmic (very
sensitive) and people who are sensitised to a particular odour through repeated
exposure. Another property of olfactory functioning includes adaptation to an odour,
also known as olfactory fatigue. These terms describe a temporary desensitisation
after being exposed to an odour 5 .
8
Courtesy of www.nobelprize.org/nobel_prizes/medicine/laureates/2004/odorant_high_eng.jpg.
4 Environmental Publication 2012/06–A review of odour properties of H 2 S Odour Threshold Investigation 2012