Abstract
The assessment of the impact of environmental odour emissions is based on four steps: (1) the determination of the odour flow of the source, (2) the dilution in the atmosphere, described by dispersion models, calculating time series of one-hour mean values, (3) short-time peak concentrations derived from one-hour mean values, to mimic odour sensation of the human nose, and (4) odour impact criteria, defined by the odour concentration threshold and its exceedance probability. The procedure of the determination of odour annoyance by the last two steps (peak-to-mean factor and odour impact criteria) is compared for various national jurisdictions showing a great variety of criteria. To reach a better comparability for separation distances, calculated by impact criteria for different countries, an alignment of the peak-to-mean factors and the odour impact criteria should be aspired. An important requirement to improve the reliability of the calculated separation distances is the use of a peak-to-mean factor, which decreases with distance from the source. The separation distances calculated for the same protection level but with different national odour impact criteria, contrary to expectation, are very different and show a stronger dependence on wind direction for higher exceedance probabilities. It must be concluded that the concept of odour impact criteria used in various jurisdictions should be harmonized. It is obvious that separation distances, calculated for an identical protection level, should be similar.
