REDUCTION OF RADON HAZARD IN SMOKE-FREE OFFICES

Properties related to radon have been surveyed in 94 offices with a vi ew to studying the difference between smoke free and non-smoke-free of fices. These properties include the radon concentration, the total pot ential alpha energy concentration of radon daughters, the equilibrium factor and the fraction of unattached radon daughters. It has been est ablished that the radon properties are seriously affected by the runni ng time of the air conditioner at the time of measurements and by the season. To eliminate the effects from the former, the data before the radon properties reach their equilibrium values have been neglected, s o the number of samples used is 65, of which 39 allow smoking and 36 a re smoke free. To identify the effects from the season factor, data ar e separated into the seasons for the measurements, viz. summer, autumn and winter. It has been found that smoking does not significantly aff ect the equilibrium factor and the contribution of the lung exposure t o the annual effective dose equivalent (H-E) during autumn and winter months. The annual reduction in H-E thus calculated is 0.12 mSv.y(-1). Considering that the average H-E is about 0.45 mSv.y(-1) for non-smok e-free offices, the provision of smoke-free offices to mitigate the ra don hazard in offices in Hong Kong can be regarded as effective.