Based on the probability density function obtained earlier for concentration of a pollutant spread in the atmosphere, we consider the problem of determining mathematical expectations of the frequency of occurrence of concentration to be above a given threshold level and the duration of such emissions. Calculations by the deduced formulas well agree with the experimental data from Refs. 1 and 2. It is shown that the "transient" and "equilibrium" regimes of concentration pulsation obtained by the formulas correspond to different values of pollutant concentration intermittence.