Source Of Indoor Radon Research Articles

Characterising the Source of Radon Indoors

Average indoor radon concentrations range over more than two orders of magnitude, largely because of variability in the rate at which radon enters from building materials, soil, and water supplies. Determining the indoor source magnitude requires knowledge of the generation of radon in source materials, its movement within materials by diffusion and convection, and the means of its entry into buildings. This paper reviews the state of understanding of indoor radon sources and transport. Our understanding of generation rates in and movement through building materials is relatively complete and indicates that, except for materials with unusually high radionuclide contents, these sources can account for observed indoor radon concentrations only at the low end of the range observed. Our understanding of how radon enters buildings from surrounding soil is poorer; however, recent experimental and theoretical studies suggest that soil may be the predominant source in many cases where the indoor radon concentration is high.

Sources of Indoor Radon in Houses: A Review

The primary sources of indoor radon are analyzed and discussed. These include soil gas, building materials, and tap water. Within the framework of a simple steady-state analysis of the radon concentration in a model of a typical house, the potential contribution to indoor radon levels from each source is determined. When these results are compared with reported field studies of radon in houses, it appears that the infiltration of soil gas directly into a house is generally by far the largest contributor to indoor radon levels. In a few regions of the country, where drinking water supplies are drawn from aquifers in granite and other radium-bearing strata, water usage can be another major contributor to indoor radon. Even in well ventilated houses, with air exchange rates in excess of one house volume per hour, soil gas and water can lead to radon concentrations above existing health protection guides, such as those developed for remedial actions addressing the use of uranium mill tailings in houses. In ex...

Diffusion of radon through cracks in a concrete slab.

A mathematical model is developed to describe diffusion of radon through cracks or gaps in concrete slabs which are used in building foundations. As radon approaches the soil surface from underlying soil, it encounters a concrete slab. The radon will diffuse toward any air-filled cracks. The rate of exhalation through a portion of a cracked slab is determined and compared to the rate of exhalation from the same surface area of bare soil. In a typical case, this ratio is approx. 0.25. This is about a 20-fold increase to the ratio found when the concrete slab has no cracks. Therefore crack pathways are potentially a major source of indoor radon.

Indoor radon source fluxes: Experimental tests of a two-chamber model

Modeling houses as two coupled chambers, namely, the living area and basement, predicts more accurately the total indoor radon source flux from building materials and geology than a one-chamber model in houses with disparate radon concentrations. Three regional surveys found mean radon concentration ratios between basement and living area to range from 1.4 to 4.2, implying weak interchamber coupling in most cases. The invariability of second-order system parameters under steady infiltration but different initial conditions confirms the adequacy of the two-chamber model. The presence of a characteristic radon source flux was detected within the basements of two houses, in one case across different infiltration, coupling, and initial conditions. One-chamber models fit to two-chamber tracer gas data in one house show a source flux variation of a factor of 6 across changing coupling, while the two-chamber source flux variation was only a factor of 1.5. A substantial fraction of the apparent one-chamber living area source flux in these cases is the variable convective radon flux from the basement. The technique is not sensitive enough to detect living area source fluxes if either the interchamber coupling is strong or if the basement source flux is substantially larger.