INDOOR AIR QUALITY: EFFECT OF AERATIONS ON RADON 222 DENSITY ACTIVITY LEVEL.

Summary The continuous renewal of the air of a room and the frequency of air drafts on the level of vo-lumic activity of RADON 222 are studied. When no aeration drives radon penetrating into a place, under constant input streams (e), the volume activity (A) at equilibrium is established at a value equal to the value of that flux divided by the ra-dioactive constant of radon (λ). A= ÕE/λ In a properly ventilated living room, the level of radioactivity is mainly controlled by air renewal (n): A= E/n Starting from scratch, the evolution of radioactivity can be represented by the expression: A = (-E/β) (1 — exp (-βt)) with β = λ + n The time required to achieve the equilibrium regime can be deduced from: t = 4.585/β Good permanent air renewal is essential to reduce the level of activity by volume of ra-don. In many cases, the only practice of two — or even three — daily air drafts is not enough to eliminate the health problem posed by radon. For a constant inflow, the theory predicts that after total evacuation of radon the evolution of ra-dioactivity according to time gives access to the value of the input flow and the rate of renewal of the air of the place. The measurements we have carried out in about 100 individuals in Aix-les-Bains, as well as those carried out in public buildings in the city by the Municipal Technical Services and the Regional Health Agency reveal that radon density activities can be very high locally (up to 8.800 Bq.m-3 for our own measurements), showing that this gas can cause significant problems outside the granitic or volcanic regions and that its presence is not always limited to the ground floor of a dwelling. Some concrete examples illustrate the influence of aerations on the level of radioactivity due to radon. The first four results in our possession after the installation of the VMI seem very promising to fight against this gas. Between the first national marketing year in 1995 and the year 2005, 2820 checks were carried out in the department of Savoie. The majority provided by the Regional Health Agency, they are presented in six tables which concern 221 of the 330 municipalities in the department.