Understanding Your Radon Test Results: A Guide for Metro East Homeowners

When you buy a house in Metro East Illinois, radon usually comes up during the inspection. Sellers run a test, you see a number on a report, and then everyone wonders what it actually means. I have spent years working with homeowners in Belleville, Edwardsville, O'Fallon IL, and Collinsville, and I can tell you that the number on that paper is only the beginning of the story. The real question is what you do next.

Radon is a radioactive gas that comes from the natural decay of uranium in soil. It moves up through the ground and seeps into homes through cracks in the foundation, gaps around pipes, and other openings. You cannot see it, smell it, or taste it, which is why testing is the only way to know if you have a problem. The EPA has set an action level of 4.0 picocuries per liter (pCi/L) for indoor radon. If your test shows a level at or above that, they recommend fixing the problem. But even levels below 4.0 carry some risk, and many homeowners choose to address levels between 2.0 and 4.0 as well.

So you have your radon test results in hand. Now what? First, take a breath. A high number does not mean your house is ruined. It means the soil gas is finding a way in, and that is something we can fix. Radon mitigation systems, like sub-slab depressurization, work by creating a low-pressure zone under your foundation. A radon fan pulls the soil gas from below the slab and vents it safely above the roofline. The key component is the radon sump, which is a small pit dug in the gravel under the slab where the fan can pull from. That system can drop indoor levels from 20 pCi/L down to below 2.0 in most cases.

But before you call a mitigation company, you need to make sure the test you have is reliable. There are different ways to measure radon, and each has its own strengths. A short-term radon test, usually lasting two to seven days, uses an activated carbon device that absorbs radon from the air. These are cheap and give you a quick snapshot, but they can be thrown off by weather, open windows, or even a thunderstorm. A long-term radon test, which runs for three months to a year, uses an alpha track detector that gives a much more accurate average of your year-round exposure. The alpha track detector is the gold standard for a reason: it smooths out daily and seasonal spikes.

Another option is a continuous radon monitor, which is an electronic device that takes readings every hour and can show you how levels change over time. These are great for troubleshooting because you can see if levels spike at night when the house is closed up, or drop during a windy day. But they cost more and require batteries and setup. For a one-time check, most people go with a short-term test or a long-term alpha track detector. I recommend the long-term test if you have the time, because it gives you the truest picture of what your family is breathing.

Now, here is where things get tricky. The radon map for Illinois shows that much of the Metro East area sits in Zone 1, which means average indoor levels are predicted to be above 4.0 pCi/L. That does not mean every house in Belleville or Edwardsville has high radon. Radon is local. One house can have 2.0 and the next house over can have 15.0. The geology, the foundation type, and even how the house was built all affect the levels. That is why testing every home individually is so important. You cannot rely on your neighbor's results.

When you get your radon test results back, look at the number and the test duration. If it was a short-term test taken during a rainstorm with all the windows closed, it might read higher than usual. If it was a long-term test, you have a solid average. Either way, the next step is deciding if you want to mitigate. The EPA says you should fix your home if the level is 4.0 or higher, but many homeowners in Metro East Illinois choose to install mitigation systems for levels between 2.0 and 4.0 as well. It is a personal decision based on your budget and your tolerance for risk.

If you decide to move forward with mitigation, the process is straightforward. A contractor like Air Sense Environmental will come out, inspect your home's foundation, and design a system. The most common method is sub-slab depressurization. They cut a small hole in your basement floor or slab, dig out a radon sump, and install a pipe that runs from that sump to the outside. A radon fan is attached to the pipe, and it runs continuously to keep the pressure under the slab lower than the pressure inside your home. That way, soil gas is drawn to the sump and vented outside instead of coming into your living space.

After the system is installed, you should test again to make sure it is working. A post-mitigation test, usually a short-term test, will confirm that levels have dropped. Most systems bring levels down below 2.0 pCi/L. The fan runs 24/7, and it uses about the same amount of electricity as a 60-watt lightbulb. So the ongoing cost is low. The peace of mind is high.

One thing I want to emphasize is that radon mitigation is not a one-and-done deal. The soil under your house can shift over time, and the system itself needs to be maintained. The radon fan has a lifespan of about five to ten years. If it stops working, levels can climb back up. I recommend testing every two years, even after mitigation. A simple radon test kit from a hardware store or online will do the job. You mail it in, and you get your results in a few weeks. That is cheap insurance.

I have seen homeowners in O'Fallon IL test their homes, get a level of 8.0, and worry that they will have to move. They do not. Mitigation works. I have also seen people in Collinsville test at 2.5 and decide not to do anything, which is their call. But I always suggest that if you have children or spend a lot of time in the basement, even moderate levels are worth addressing. The risk from radon is cumulative. The longer you are exposed, the greater the chance of lung cancer. It is the second leading cause of lung cancer in the United States, after smoking.

There is also the question of real estate transactions. If you are selling a home, the buyer will likely ask for radon test results. If your test comes back high, you have two choices: negotiate a credit for mitigation, or install a system yourself before closing. Many sellers in Metro East Illinois choose to install the system ahead of time so the buyer sees a clean report. That can make the sale smoother. If you are buying, make sure the test is done by a certified professional and that the results are from a lab that follows EPA protocols. Do not accept a test the seller ran themselves with a kit they bought online. You want an unbiased measurement.

To sum this up practically: test your home, understand the number, and decide what level of risk you are comfortable with. If your radon test results come back above 4.0, call a mitigation professional. If they are between 2.0 and 4.0, consider mitigation, especially if you spend time in the basement. If they are below 2.0, you are in good shape, but test again in a couple of years. Radon levels can change. The ground shifts, foundations settle, and new cracks appear. A one-time test is not a lifetime pass.

Living in Metro East Illinois means we have beautiful neighborhoods in Belleville, Edwardsville, O'Fallon IL, and Collinsville, with older homes full of character and newer homes built to modern codes. But the radon potential here is real. The radon map does not lie. The good news is that testing is easy and mitigation is effective. You do not have to live with the worry. You just have to take the first step.