The present guideline is a set of instructions for the measurement of odour impact in an area affected by an odorant plume. The odour load is determined here with qualified assessors who assess the ambient air for odours at previously defined positions within certain measurement cycles. Plume measurements are used for gathering information on odour impact within an odorant plume. The investigation takes place in specific (measured) meteorological conditions. Like for grid field inspections, the percentage time with odour detection (percentage odour time) during a single measurement is used as the measured variable for odour impact. The main field of application of plume measurement is for the reverse calculation of emission source strengths by using suitable dispersion models. Furthermore, it can also be used in the calibration and validation of dispersion models, for the determination of plume extent and in the pinpointing of causers of emissions.