A method is developed to locate an unknown emission source. Theproposed method is based on the assumption that the GaussianPlume model (GPM) completely describes the dispersion ofpollutants in atmospheric air. A concept called `Equipotentialpollution source' is applied to locate the source. The samplingsites are chosen in such a manner that the straight linejoining them is perpendicular to the wind direction. The methodprovides an opportunity to sample from one side of a probablepollution source. The uncertainty in the method is alsodiscussed. A program in Fortran is developed to identify thezone containing the unknown source. The technique is developedin such a way that the zone can be identified without knowingall the parameters of the GPM.