LONG-TERM AND EQUILIBRIUM FACTOR INDOOR RADON MEASUREMENTS

This paper presents the annual radon gas concentrations obtained durin g the 1994-1995 monitoring campaign using passive electret system (typ e E-PERM ). Radon levels were measured in 154 single family dwellings, in normal occupancy conditions (open house condition) in the metropol itan zone of Mexico City. At the same time radon monitoring was perfor med outdoors. The results show the general log-normal distribution of integrated indoor radon concentration with an annual indoor mean of 3. 8 pCi.l(-1). The seasonal variations show the minimum mean values in t he summer season which are 39% lower than that in autumn. Equilibrium factors (F) were measured in 12 typical houses both in autumn and wint er using a continuous working level monitor for short-lived radon deca y products and H-chamber loaded with a short term electret (HST, E-PER M) for radon gas. The obtained total mean equilibrium factors are: F = 0.41+/-0.17 and F = 0.29+/-0.04 for indoor and outdoor, respectively. A quality program was also improved.