This part of the European Standard describes the plume method for determining the extent of detectable and recognizable odours from a specific source using direct observation in the field by human panel members under specific meteorological conditions. The plume method involves the determination of the presence or absence (YES/NO) of recognizable odours in and around the plume originating from a specific odour emission source, for a specific emission situation and under specific meteorological conditions (specific wind direction, wind speed and boundary layer turbulence). The unit of measurement is the presence or absence of recognizable odours at a particular downwind location. The extent of the plume is assessed as the transition of absence to presence of recognizable odour. The primary application of this standard is to provide a common basis for the determination of the plume extent in the member states of the European Union. The results are typically used to determine a plausible extent of potential exposure to recognizable odours, or to estimate the total emission rate based on the plume extent, using reverse dispersion modelling. The field of application of this European Standard includes the determination of the extent of the recognizable odour plume downwind from a source, under specific meteorological conditions (e.g. wind direction, wind speed, turbulence etc. (see 7.3.2) This European Standard does not include: the measurement of intensity of ambient odours; the measurement of hedonic tone of ambient odours; the calculation of odour exposure in specific weather conditions in order to determine the frequency distribution of recognizable odour in an odour plume; the calculation of estimated source emission rate from plume assessment using reverse dispersion modelling. An overview of the interaction between existing odour exposure assessment methods is given in Annex A including grid method (Part 1), plume method (Part 2) and olfactometry according EN 13725.