Radon is a naturally occurring radioactive gas that is completely odorless, colorless, and tasteless. This undetectable nature makes radon a significant environmental hazard in homes and buildings. Since human senses cannot detect its presence, specialized testing is the only way to determine if a building has elevated levels. Long-term exposure can occur without any warning signs, underscoring the importance of preventative measures.
The Nature and Origin of Radon Gas
Radon is a radioactive noble gas that forms through the natural decay chain of uranium, an element found in nearly all soil and rock worldwide. The primary isotope of concern, Radon-222, is produced directly from the decay of Radium-226, an intermediate product in the breakdown of Uranium-238. This continuous process means radon gas is constantly being generated beneath the Earth’s surface.
Because it is a gas, radon moves through porous soil and rock, seeking pathways to the atmosphere. When a building is constructed on this ground, the structure can act like a vacuum, drawing the gas inside. Radon typically enters through cracks in the foundation, construction joints, gaps around utility pipes, or sumps. Any type of building, regardless of its age or whether it has a basement, can experience elevated concentrations.
The Health Risk of Radon Exposure
The danger of radon exposure lies in its radioactivity and that of its short-lived decay products, often called radon progeny. Once inhaled, these decay products—isotopes of elements like polonium and lead—are deposited onto the cells lining the airways and lungs. As these particles decay, they emit alpha radiation, which damages the DNA of lung tissue cells.
This damage can eventually lead to the development of lung cancer. Radon is considered the leading cause of lung cancer among non-smokers and the second leading cause overall, after cigarette smoking. The U.S. Environmental Protection Agency (EPA) estimates that radon is responsible for approximately 21,000 lung cancer deaths each year. Risk is quantified in picocuries per liter (pCi/L). For example, a smoker exposed to the EPA’s action level of 4 pCi/L faces a significantly higher lifetime lung cancer risk than a non-smoker at the same level.
Testing Your Home for Radon
Testing is the only reliable way to measure radon concentration within a home. The EPA recommends taking action to reduce levels when the result is 4 pCi/L or higher. Testing devices fall into two main categories: short-term and long-term.
Short-term tests, such as charcoal canisters, are typically exposed for two to 90 days and are useful for quick initial screening. These tests must be conducted under “closed-house conditions,” meaning windows and exterior doors are kept closed to prevent gas dilution. Long-term tests, such as alpha track detectors, are exposed for more than 90 days. They provide a more accurate representation of the home’s annual average radon level, accounting for seasonal fluctuations. All testing should be performed in the lowest lived-in area of the home, such as a basement or first floor, where radon is most likely to accumulate.
Reducing High Radon Levels
When testing confirms a radon level at or above the 4 pCi/L action threshold, mitigation is necessary to lower the concentration. The most common and effective method for reduction is the installation of an Active Sub-Slab Depressurization (SSD) system. This system works by creating a negative pressure field beneath the concrete slab or foundation.
A certified professional drills a hole through the slab and installs a suction pipe connected to a continuously running fan. The fan actively draws radon and other soil gases from beneath the house. This extracted gas is then safely vented through the pipe to the outdoors, typically above the roofline, before it can enter the living space. Sealing major entry points like foundation cracks is also a component of mitigation, but sealing alone is not sufficient to achieve the necessary reduction.