Radiation is a natural part of the environment that people interact continuously, and radon is one of the most important sources because of its abundance and mobility. Due to gas form, radon can reach and accumulate in living places easily. Inhalation of radon and its progenies is an important risk factor for health hazards. Accurate measurement of radon levels is quite essential for the dose evaluation of radon exposure in buildings. In this study, radon activity measurements have been performed by using AlphaGUARD portable radon detector at several locations in Akfirat campus of Istanbul Okan University. Annual effective doses were calculated by using ICRP regulations for various exposure periods.