Radon is a radioactive gas that you cannot see, smell, or taste. It forms naturally from the decay of uranium in soil and rock, and it can seep into any home through cracks in the foundation, gaps around pipes, and other openings where the building contacts the ground. Once inside, radon can accumulate to levels that pose serious health risks.
Understanding the Risk
When you breathe air containing radon, radioactive particles can get trapped in your lungs. Over time, these particles release radiation that can damage lung tissue and potentially lead to lung cancer. The risk increases with higher radon levels and longer exposure times. Smokers exposed to elevated radon face significantly higher risk than nonsmokers.
Radon levels vary widely from home to home, even among neighboring houses. The only way to know your home's radon level is to test. Geographic location, soil composition, home construction, and seasonal factors all influence indoor radon concentrations.
The EPA Action Level
The EPA recommends taking action to reduce radon when levels reach or exceed 4 picocuries per liter of air, written as 4 pCi/L. This action level represents a balance between health risk, testing accuracy, and the practical capability of mitigation technology. The EPA also recommends considering mitigation for homes with radon levels between 2 and 4 pCi/L, because there is no known safe level of radon exposure.
To put this in perspective, the average outdoor radon level is about 0.4 pCi/L, and the average indoor level in American homes is approximately 1.3 pCi/L. Homes with radon problems can have levels many times higher than the action level.
Testing Your Home
Short-term radon tests, typically lasting 2 to 7 days, provide a snapshot of radon levels and are useful for initial screening. These tests should be conducted in the lowest lived-in level of your home, with windows and doors closed as much as practical. Hardware stores and online retailers sell inexpensive short-term test kits.
Long-term tests, lasting more than 90 days, provide a more accurate picture of average radon levels over time, accounting for seasonal variations. If your short-term test shows elevated levels, a follow-up test, either short-term or long-term, is recommended before making mitigation decisions.
Continuous radon monitors provide ongoing measurement and can alert you to changes in radon levels. These are particularly useful after mitigation to verify that the system is working, or in areas where radon levels are known to fluctuate significantly.
How Radon Enters Homes
Radon moves from the soil into your home because indoor air pressure is typically lower than the pressure in the soil around and under your foundation. This pressure difference draws soil gases, including radon, into the building through any available pathway. Common entry points include cracks in solid floors and walls, construction joints, gaps around service pipes, and the water supply in some cases.
Homes with basements or slab-on-grade foundations are more susceptible because they have more contact with the soil. However, crawlspace homes can also have elevated radon levels, and radon can even affect upper floors of multi-story buildings.
Mitigation Methods
The most common and effective radon mitigation approach is sub-slab depressurization. A pipe is installed through the foundation floor and connected to a fan that runs continuously, drawing radon-laden air from beneath the building and venting it above the roofline where it disperses harmlessly. When properly installed, these systems can reduce radon levels by up to 99 percent.
Sealing cracks and openings in the foundation can help reduce radon entry but is rarely sufficient as a standalone solution. Sealing works best in combination with active depressurization. Improving ventilation, particularly in crawlspaces, can also help reduce radon levels in some situations.
Radon mitigation should be performed by a qualified professional. While the systems are relatively straightforward, proper installation requires understanding of building construction, airflow dynamics, and local conditions. Most states maintain lists of certified radon mitigation professionals.
Taking Action
Testing for radon is simple and inexpensive. If you have never tested your home, do it. If you tested years ago, consider testing again, as radon levels can change over time due to settling, new cracks, or changes in soil conditions.
If your test results show elevated radon, do not panic. Radon mitigation is highly effective and typically costs between one thousand and two thousand dollars for most homes. The health benefit of reducing radon exposure is significant and well worth the investment.
Real estate transactions in many areas now require radon testing, and sellers often address elevated levels before closing. If you are buying a home, request radon test results and factor mitigation costs into your planning if levels are elevated.
Affiliate Disclosure: FreshAir Advisor is an independent resource. Some links on this site are affiliate links, meaning we may earn a commission if you purchase through them. This does not affect our recommendations, which are based solely on product quality and suitability for your needs. Read our full disclosure.