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Industrial odour control 1 IntroductionSuitable objective physical/chemical measurement methods to determine smell do not exist. The guideline is, therefore, based on a number of concepts related to the subjective smell perception of a number of people (a smell panel). The most important concept is the odour threshold value. Reference odorants are used in order to make the detection threshold value independent of the technical equipment used and of the composition of the panel. Calculation of emission/dilution The maximum allowable emission and/or required dilution of odorous compounds is calculated on the basis of the odour threshold value, according to the directions given in the Danish EPA guidelines No. 7/1974 (control of air pollution from enterprises), No. 3/1976 (control of air pollution from oil-fired plants), and No. 2/1978 (control of air pollution from plants emitting cellulose thinners and other thinners into the atmosphere). The main principle is that the concentration of odorants at soil surface shall not exceed the odour threshold concentration by a factor 5- 10 in specific atmospheric conditions (neutral -moderately unstable, wind speed 4,5 m/s). From experience gained in Denmark and abroad we know that the resulting conditions are in general satisfactory (Palgren Jensen and Flyger, 1983), (WSL, 1980), (Bedborough and Trott, 1979), (Keddie, 1984). The practical experience in Denmark gained by the Danish Boilers' Association supports this principle. Satisfactory conditions can be achieved either by cleaning of exhaust air, by dispersion into the atmosphere by means of stacks, or by a combination of these methods. Below a description is given both of cleaning measures and or calculations of outlet heights. Odour nuisances/harmful effects Some substances may cause both harmful effects in the environment and odour nuisances. Both these problems must of course be considered separately in connection with complaint and approval cases.
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