The effect of a fan in reducing the concentration of the radon daughters inside a room by plate-out to the surface of the wall using plastic α-detectors

The number of radon daughters which are deposited per unit area on the two sides of the blades of the fan are more than those plated out per unit area on the surface of the walls. However, the total surface area of the fan blades is only 0.2% of the surface are of the walls. The activity on the blades will therefore reduce the level inside the room by ~1% while the main decrease in airborne activity is due to the plate-out on the surfaces of the walls of the room. We did not measure the concentration of condensation nuclei in the room or on the wall so that we cannot discriminate between free irons or atoms and those adsorbed on condensation nuclei in the air on the wall with and without the fan on. Although the increase in α-tracks cm^-2 h^-1 on the wall with and without the fan is due to the increase of plate-out of radon daughters, still more information can be gained if tracks resulting from airborne Rn are separated from tracks resulting from plated out radon daughters. Also, it is not clear if the plate out of radon daughters on the walls and fan blades would be the same as plate out on the detectors.