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The way in which protection is carried out depends on the type of building, its position in the soil profile, and the radon concentration in the soil. Basic protection against radon from soil is provided by a radon-proof membrane, which has to be applied over the entire surface of the building substructure that is in contact with the soil. The only materials that may be used as radon-proof membranes are those with barrier properties that have been verified by measuring the radon diffusion coefficient, and that have proven durability corresponding to the expected lifetime of the building. Bitumen membranes with Al foil cannot serve as a radon-proof membrane due to their very low tear resistance, and plastic membranes with dimples are unsuitable due to evidence that it is almost impossible to form airtight joints with this material. If the radon risk category of the foundation soils is high, a radon-proof membrane must be applied in combination with sub-slab ventilation or floor air gap ventilation. Sub-slab ventilation is usually provided by a network of flexible perforated pipes placed in a sub-floor layer of coarse gravel. Perforated pipes are connected to a vertical exhaust pipe, which terminates above the roof. A typical arrangement of a sub-slab ventilation system is shown in Fig. 1, and a floor structure with soil ventilation is presented in Fig. 2. In most cases, the floor air gap is implemented under a radon-proof membrane (Fig. 3).

Fig. 1 - Geometry of the soil ventilation convenient for new buildings. There are no vent holes in the perimeter walls. Any pipe penetration must be carefully sealed.

Fig. 2 - Floor structure with a soil ventilation.

Fig. 3 - Floor structure with an air gap ventilation.