A semi-analytical Lagrangian particle model to simulate the pollutant dispersion during low wind speed conditions is presented and tested. The method relies to a stochastic integral equation whose solution is obtained using ILS method, which consists in the iterative solution of Langevin equation by the Picard's iteration method. To consider the low wind speed effect, the solution for the horizontal components of the turbulent velocity takes account the Eulerian autocorrelation function as suggested by Frenkiel [1953. Advances in Applied Mechanics 3, 61–107]. The model results are shown to agree very well with the field tracer data collected during stable conditions at Idaho National Engineering Laboratory (INEL) and during convective conditions from the series of field experiments at Indian Institute of Technology (IIT). A statistical analysis reveals that the model simulates very well the experimental data and presents results comparable or even better than ones obtained with other models used as comparison. The analytical feature of the ILS method and the inclusion of the Eulerian autocorrelation function suggested by Frenkiel (1953) allow generating more accurate results.