Measurements of Indoor Radon Levels in India using Solid~State Nuclear Track Detectors: Need for Standardisation

Solid-state nuclear track detectors are being used to obtain the time integrated concentration levels of indoor radon/thoron and their daughters. This technique is preferred for taking such measurements in dwellings Such measurements are important as the radiation dose to human beings due to indoor radon constitutes more than 50 per cent of the total dose including that received from the natural sources. Normalisation is necessary to obtain a representative value of the effective dose equivalent to the population. Indoor measurements carried out by several laboratories ali over the country show that tht: indoor radon levels vary from 1.5 to about 2(XX) Bq m-.l, while the normal level is in the range of 10 to 60 Bq m-.l. It is rather difficult to compare the levels since the exposure conditions, the period of measurements and the calibration techniques used are not standardised. The present paper discusses the measurements of indoor radon in India by various groups and the important problems associated with the standardisation of these measurements. The standardisation procedure and the calibration set-up developed at this laboratory are also presented.