Monitoring and modelling of indoor radon concentrations in a multi-storey building at Mumbai, India

Radon (Rn222) levels in an indoor atmosphere of a multi-storey building at Mumbai have been measured for one year covering all the four seasons. Monitoring was carried out using the time-integrated passive detector technique, using Kodak-115 type Solid State Nuclear Track Detector (SSNTD) films of 2.5×2.5 cm size. Measured indoor radon levels showed a decreasing trend with height with concentration ranging from 41 Bq m-3 at ground floor level to 15 Bq m-3 at 19th floor level. Using the UNSCEAR (1993) dose conversion factors, the inhalation dose due to breathing of radon gas is estimated to be 1.03 mSv y-1 at the ground floor to 0.38 mSv y−1 at the 19th floor level. Measured indoor radon concentrations on each floor were compared with the computed values using a mathematical model. The agreement between measured values and calculated values of indoor concentrations at different floors was very good within the limitations of various field parameter values.