Measurements of radon daughter products in air by means of a filtration method using alpha spectrometry

An improved method for the measurement of radon and its daughters is described. The integral method is based on the detection of alpha particles originating in the decay of daughter products 218Po and 214Po. The relationship for volumetric activities of the radon daughter products is given in the form of a matrix equation. Three measurements must be made to solve this equation. The spectrometric method also uses alpha particles originating from 218Po and 214Po. For each counting interval two count numbers can be obtained and therefore only two measuring intervals are necessary. The interval choice method is described. For the integral and spectroscopic method, numerical relationships are given between measured alpha activity on a filter, the volume activity of radon daughter products, and the equilibrium activity of radon gas in ambient air. (J.B.)