Indoor Radon Radioactivity at the University of Brunei Darussalam

— Indoor radon radioactivity in the rooms on the ground floor and first floor of the Physics Department, Faculty of Science, Universiti Brunei Darussalam was measured using a system that consists of an air filter pump, ZnS detector, photomultiplier tube and counter. Ground floor rooms' radon radioactivity was found to be about three times higher than that of the first floor. The maximum ground floor indoor radioactivity is only 0.39 Bqm^?3, a value relatively low and safe compared to the mean outdoor radon concentration of 1.41 Bqm^?3 measured (HU and TAN, 2000). The main source of radon emanation originates from the ground soil rather than the building materials.