A variety of natural and human-caused soil gases can infiltrate structures and lead to indoor air quality problems. Soil gases can be sucked into basements, crawl spaces, and floor slabs if negative pressurization exists within or under a structure. You can prevent this problem by creating a physical barrier between the soil and the home and by controlling the air pressure conditions under and within the home.
Harmful human-source soil gases include
trie company sent a team of specialists to his house to investigate. The readings on the Geiger counter showed levels 700 times higher than the maximum considered safe for human exposure. Researchers concluded that the culprit was radon, a naturally occurring radioactive gas derived from underground uranium.
Discussion
At that time, very little was known about radon and its health effects. The Watras house was used as a laboratory for radon researchers who wanted to learn how radon gets into a house and how to get it out. Low-grade uranium ore was discovered beneath the basement of the structure, in direct contact with the house. The foundation of the house was removed, along with the soil underneath, to a depth of four feet. Ventilation fans were installed to pull radon-laden air out from under the house. Watras and his family were eventually able to move back into their home.
pesticides, herbicides, and gases from nearby landfills or industrial sites. In new construction, most of these problems can be avoided through careful site selection and through home and yard maintenance that is free of toxic chemicals.
Water vapor and radon gas are two naturally occurring soil gases that may infiltrate a structure and result in health problems. The intrusion of water vapor into the home may cause structural damage and mold problems. These gases are both easily dissipated or blocked from entry by installing appropriate controls during the construction process.
Radon is a clear, odorless gaseous byproduct of the natural breakdown of uranium in soil, rock, and water. While radon gas dissipates in open spaces, it tends to cling to particulate matter and accumulates when enclosed. When inhaled, radioactive particles become lodged in the mucous membranes of the respiratory system. The Surgeon General has stated that radon exposure is second only to tobacco smoke as a cause of lung cancer.
It has been estimated that as many as one in 15 homes in the United States contains elevated radon levels. The EPA recommends mitigation at levels higher than 4.0 picocuries per liter of air. Even at 4.0 picocuries per liter, there is an increased risk of lung cancer. Therefore, reducing radon to between 1.0 and 1.5 picocuries per liter is a prudent target, ensuring a margin of safety.
Radon mitigation is most effective and least costly when incorporated into the construction of the home. If you are building a new home and there is reason to suspect a radon problem, a soil test is advisable. Although the test will not tell you definitively what the radon levels will ultimately be in the finished home, it will help you decide whether to include mitigation measures in your construction plans. For more information about this test, refer to Division 13.
