Radon

Radon is an invisible, odorless, tasteless gas that occurs naturally in the earth's crust. Radon is a product of the decay of uranium. The decay of uranium to lead is a fourteen-step process. Radon is formed at the sixth step. It is unique because it is the first decay product which is a gas, not a solid.

The radon gas itself is not a problem, but its decay products are. The radioactive decay products are particles which can attach themselves to lung tissue when radon gas is inhaled. It is primarily the alpha radiation that causes lung cancer. In the United States, it is estimated that up to 20,000 deaths every year are caused by radon gas. As with cigarette smoking, the risk is higher with greater exposure. The effects are long term rather than immediate.

Uranium is present in many parts of the earth's crust. Areas subject to high radon gas levels have appreciable concentrations of uranium in the earth and cracks or porous soils through which the gas can migrate up to the surface. 

 Radon which escapes into the air is not a problem since it is diluted quickly. In buildings, however, radon gas can be trapped, particularly during winter months when doors and windows are kept closed and ventilation is at a minimum. It is difficult to predict which buildings will have a problem.
 

Radon enters the building through the cracks in basement floors and walls, openings around pipes and electrical services into the basement, through water supplies, and through basement floor drains, for example. Even in areas with high concentrations in the earth, one building may have very high radon levels and a similar building across the street, very low levels. 

 There are several types of detectors available for testing radon levels in buildings. The identification of radon gas in a home is not part of an ASHI home inspection.
Most of the test procedures require laboratory analysis. The amount of time needed for accurate results is a point of disagreement among experts. The levels of radon gas which require action are: any level above 4 Pico curies/liter bring a recommendation of mitigation.
 

There are several techniques used to lower radon levels in homes. They include sealing holes to prevent radon gas from getting into houses, pressuring basements or crawl spaces to keep the gas out, and adding pipes below basements to carry radon away from the home.