In general, odours are perceived by humans through a single respiratory act having a duration ofapproximately 5 seconds. Moreover, odour concentration varies almost randomly over time, as any otherphysical variable in a turbulent environment. For this reason, both field measurements and dispersion modelsused for odour impact assessment purposes should be able to refer to short sampling times, instead ofconsidering concentrations averaged over prolonged periods (i.e. 1 hour). This paper has the aim toinvestigate the problem of odour concentration fluctuations and their correlation with odour nuisance, therebybriefly discussing the problem of turbulence based on some theoretical considerations and of a fewexperimental results. The experimental results relevant to the continuous monitoring of instantaneous H2Sconcentration in ambient air clearly show that peak concentration exceed 1-hour average concentrations byalmost 1 order of magnitude. Finally, the paper discusses the possible implementation of a dispersion modelspecifically dedicated to odour nuisance evaluation, thereby investigating different solutions to account forconcentration fluctuations. The investigation related to the peak-to-mean approach, currently being the mostwidely used method to evaluate peak concentrations from 1-hour averaged concentrations on a regulatorylevel, allowed to point out the drawbacks of this methodology, which, despite its simplicity and ease-of-use, isunable to accurately describe the concentration fluctuations phenomena.
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