The crosswind and normal of dispersion modeling are obtained to obtain the concentration using Gaussian plume model. There are different shapes of the standard deviations such as power law and Briggs formula for estimating concentration of the pollutants. In this work power law and Briggs formula are used to obtain the Gaussian concentration of plume model, maximum concentration at the surface and the fumigation formula. Three predicted models are comparing to the measured concentration of Iodine-135 in unstable condition. One obtains that the Gaussian concentration in centerline with BNL is the best with the measured concentration than Gaussian concentration using Briggs formula which is in good result. Also, the statistical techniques appear that the data is located inside a factor of two. Also, the maximum Gaussian concentration with the Briggs and B N L are larger values the measured concentration of I¹³⁵ and is located inside a factor of four.