For risk assessments and odor impact analyses, the highest possibly occurring concentration during a time considerably shorter than one hour is more decisive than one-hour average values. For this, the probability density function of concentration for a given location and a specific averaging time is required. In order to be able to predict the higher moments of concentration (the probability density function), the "absolute dispersion" has to be separated in its puff-growth part and the additional contribution from the meandering of the plume during the averaging time. The Puff-Particle Model (PPM) has been developed as such a puff-meandering model.