This chart of the uranium decay sequence highlights the problematic decay products of radon.
Radon has received a great deal of attention over the past fifteen years. Most architects and builders today have at least a general understanding of the radon issue, even if they are not familiar with the details of radon control. Though radon is the most serious threat overall, there are many other soil gases that builders of environmentally responsible buildings should be aware of.
In some locations and under some conditions, these other soil gases can pose health risks as significant as those associated with radon. Such gases include methane from decomposing organic matter or landfills, hydrocarbons from underground fuel spills, pesticides that have been used around buildings, other volatile organic compounds (VOCs), even water vapor. As we increasingly turn to already-developed and brownfield sites for new building projects—a good thing to do from an environmental standpoint—addressing the non-radon soil gases is a must. This article will review soil gases that pose potential health hazards to building occupants, describe how these soil gases get into buildings, and present strategies for keeping them out.
There are potentially hundreds of harmful soil gases that can get into buildings. These include specific gases, such as radon, methane, and water vapor, and whole categories of gases, including pesticide vapors, VOCs from various sources, sewer gases, and biological contaminants.