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SIZE DISTRIBUTION, EQUILIBRIUM RATIO AND UNATTACHED FRACTION OF RADON DECAY PRODUCTS UNDER TYPICAL INDOOR DOMESTIC CONDITIONS

C. Huet 1 , G. Tymen 1 and D. Boulaud 2
1 Laboratoire de Recherches Appliquées Atmosphère-Hydrosphère, Faculté des Sciences,
B.P. 809, 29285 Brest Cedex, France. 2 Laboratoire de Physique et Métrologie des Aérosols, Institut de Protection et de Sûreté Nucléaire,
CEA Saclay, 91191 Gif sur Yvette Cedex, France.

In order to characterise the behaviour of radon decay products under domestic conditions, long-term
measurements were carried out from May 1997 to April 1998 in a typical dwelling located in Brittany
(France). In particular, the unattached fraction and equilibrium factor were continuously measured.
Moreover, the size distributions of unattached and attached radon daughters were investigated by
using specific instruments implemented in the laboratory. All these experiments were carried out
under different typical aerosol conditions. The results evidenced the strong influence exerted by the
characteristics (concentration, size) of ambient aerosol on these different parameters.
Key words: radon daughters, unattached fraction, equilibrium factor, radon daughter size distribution