Radon is a gas that is created in soil where uranium and radium are found. These elements can be found everywhere in the world, but at different concentrations. Therefore, any building has the potential for elevated levels of radon. The more uranium found in the soil, the higher thepotential for elevated radon levels within a building constructed upon that soil.
The question is not, “Is there radon?” but rather, “How much radon is there, and does it present a health risk to me?”
Uranium breaks down to radium, which in turn decays into radon gas. Radon is an inert gas, which means it does not react or combine with the elements in the ground. Because of this, radon can move up through the soil into the atmosphere, where radon is easily diluted and presents little concern. However, when radon enters a building from the soil below, it can accumulate and become a health concern.
You cannot see or smell radon. There is no way that your body can sense the presence of radon, yet long-term exposure to elevated levels of naturally-occurring gas can increase a person's chances of developing lung cancer.
HOW RADON ENTERS THE HOME
Air inside buildings is typically at a lower pressure than in the soil below. The difference in air pressure causes radon and other soil gases to be drawn into the building.
Air pressure differences occur for a variety of reasons. For instance, exhaust fans, clothes dryers, and other appliances can remove a considerable amount of air from a building. When air is exhausted, outside air enters the building to replace it. Much of this replacement air comes in from the underlying soil.
When interior temperatures are higher than outside temperatures, thermal effects occur inside of the building. Just as warm air causes a balloon to rise because the surrounding air is cool, warm air rises within a building and is displaced by cooler, dense outside air. Some of that outside air comes from the soil.
Whenever air enters a building from the underlying soil. Some radon will likely come with it.
The rate at which radon enters a house may vary, depending on the forces that draw radon into the structure. Monitoring devices that measure radon over extended periods of time provide a better indication of actual, average exposure than short-term "screening" tests. The minimum duration of any test intended to determine the need for mitigation is 48 hours.
Radon also varies from season to season as a function of climate and the way the home is used by its occupants. The ideal residential radon test would be a year-long test conducted under completely normal living conditions. However, a long-term test is usually unrealistic for the purpose of a real estate transaction.
Short-term tests measure a home's potential for elevated radon levels, independent of the way occupants may actually use the house. The tests are conducted with all the windows closed and with all doors closed except for normal exit and entry. The test device is placed in the lowest area of the house currently used as living space or that may be occupied in the future. This EPA-recommended technique has become the accepted method of testing houses during real estate transactions.