Increasing ventilation reduces indoor radon levels. Opening a window can help dramatically. The radon level is lower when the inside air is allowed to escape and fresh air can enter the building. Caulking and sealing cracks and holes in basement floors and walls helps stop the release of radon from the ground into the building. Painting basement floors and wall surfaces also helps.
Epoxy paints are the most effective in reducing radon emission.
Typically, two or more coats of paint, or paint used with a sealant compound, are needed to seal the pores adequately. Polyethylene sheets serve as a good barrier to radon emission. Since proper surface treatment reduces the emission of radon, the radon concentration increases inside bricks, slabs, floors and unpainted areas. Driving nails and hooks into the treated wall increases radon emission. In cases where high radon levels are present because uranium mill tailing was used as landfill, it may be necessary to replace the fill.