The analytic methods could be subdivided into the physical, the gas chromatographical, and the chemosensory method.
When measuring odor, there is a difference between the emission and immission measurements. During the emission measurement, the odor concentration in the air is so high that the so called “Olfaktometer” is needed to thin the assay. Because of this, all measurement methods based on thinning assays are called “olfaktometrical methods.” On the contrary, an “Olfaktormeter” is seldom used during the immission measurement. The same measuring principals are used, but the judgment of the air assay happens without thinning the assay. http://odour.au.com