Based on the measurements of ambient concentrations of airborne substances and meteorological parameters, the emission mass flow for two plants was calculated by inverse dispersion modelling. One plant was a thermal treatment plant for waste, the other a waste water treatment plant of tannery. For the thermal treatment plant the ambient concentration of seven substances were measured of more than 2 years at a distance of about 800 m. The corresponding odour emission, as a mayor source of nuisance was calculated from the odour concentration thresholds of these substances. For the tannery only hydrogen sulphide was measured as a key substance for odour for about one year.

The emission data are available however only for the wind directions for which the measuring station is leeward of the plant. Using a Monte-Carlo model, the dataset was completed also for wind directions for which no ambient concentration measurements were available. The parameters for the Monte-Carlo model were derived by the statistical analysis of the dataset. The main input variables which determine the emission of the plant are the intermittence factor, air temperature, wind velocity, time of the day and day of the week, which describe the working process of the plant. For the model evaluation the ambient concentrations calculated by the synthetic emission data were compared to the measured ambient concentrations. After calibrating the Monte-Carlo model, the expected values and the variances are in good agreement with the empirical data.