How does radon enter a building?
The floors and walls of dwellings contain many small cracks and gaps formed during and after construction. Radon from the ground is drawn into the building through these cracks and gaps because the atmospheric pressure inside the building is usually slightly lower than the pressure in the underlying soil. This small pressure difference is caused by the stack (or chimney) effect of heat in the building and by the effects of wind.
Radon levels in buildings depend on the concentration of the sub-floor soil gas and the entry points into the ground floor area. Each case must be looked at separately as these factors vary.
More radon gas can rise to the surface if the rocks and soil underneath are fragmented and porous. Possible entry points to the building for the gas include cracks or holes in the floor as well as gaps around cables and service pipes.
Generally, radon is driven by the pressure difference between the inside of the building and beneath the floor. The pressure inside is usually less.
Obviously, high levels of radon are usually found in basements and at ground level. Radon is generally of little significance in high-rise buildings.
