Full-scale investigations have demonstrated that radon contained in soil air provides dominant influence on the university’s radon field formation. The change of radon volume activity in the university’s civil defense hideout and premises have strongly pronounced seasonal pattern with maximum values of radon concentration in July and August, and minimum values in March, April and November. Radon escaping from the soil surface in the summertime does not affect the radon field change in the university’s premises. The most precise estimation of radon annual average volume activity can be obtained when performing observations during a year. The substitution of this approach by the method of measurements with various duration leads to errors in the estimation of the normative parameter because of difficulties in registration of radon variations in various conditions.