Passive time-integrating 222Rn plastic monitors and SY-1 CR-39 were used for radon measurement. The effect of water-exposed-to-air during daily use of water (in the bathroom

toilet and kitchen) on indoor radon concentration was surveyed for some families situated in Zhongguancun

Beijing. It is shown that the unusual quantities of radon could be separated out and go into the surrounding air during normal use of water

and especially in winter the radon concentration near the tap in the kitchen is about twice as much as the other place and the concentration in the bathroom is 3-4 times higher than that in changing-rQom. A diffusion model was set up and the diffusion coefficients from water in the toilet

kitchen and bathroom were calculated to be 6.597×10-9

5.934×10-9 and 3.560×10-9 m2/s

respectively.