Why a Radon Retest Matters for Your Home's Safety

Understanding Radon Risks in Metro East Illinois

Living in Metro East Illinois means you are part of a region where radon concerns are real and worth taking seriously. I have spent years working with homeowners in Belleville, Edwardsville, O'Fallon IL, and Collinsville, and one thing that consistently stands out is how many people test for radon once and then forget about it. They assume a single short-term radon test gives them a permanent answer. That assumption can be risky.

Radon levels in a home are not fixed. They shift with seasons, changes in the soil, weather patterns, and even renovations you might make to your property. A test result from two years ago may not reflect what your family is breathing today. That is exactly why a radon retest should be part of your routine home maintenance plan. Air Sense Environmental has seen countless cases where a retest revealed levels that had crept up above the action level of 4 pCi/L, even though earlier tests had shown safe readings.

How Radon Enters Your Home

Radon is a radioactive gas that comes from the natural decay of uranium in the ground. It moves up through the soil and can seep into your home through cracks in the foundation, gaps around pipes, sump pumps, or even through the slab itself. Once inside, it can accumulate to dangerous levels. The U.S. EPA radon guide recommends taking action if your long-term average reading reaches 4 pCi/L or higher. But here is the thing: that average can change.

I have walked into homes in Edwardsville where the owners had done a short-term radon test during a dry spell in July. The reading was 2.8 pCi/L, well below the threshold. They felt relieved and moved on. But when the same home was tested again in the middle of a wet winter, the reading jumped to 6.1 pCi/L. That difference is not unusual. Soil saturation, barometric pressure, and even how you run your heating system can all influence how much radon gets pulled indoors.

What a Radon Retest Involves

A radon retest is not complicated, but it should be done carefully. You have several options for the type of radon detector you use. For a quick snapshot, a short-term radon test usually runs from two to seven days. These are often charcoal-based or use an E-PERM electret system. They give you a fast reading, but they can be influenced by short-term weather changes. For a more reliable picture, a long-term radon test is better. Long-term tests, such as alpha track detectors or continuous radon monitors, stay in place for three months to a year. They average out the fluctuations and give you a truer sense of your annual exposure.

When Air Sense Environmental performs a retest, we typically recommend using a long-term method if the first test was short-term. That way, you get a more complete view. But even if you use the same type of test, repeating it under different seasonal conditions is valuable. Many homeowners in Belleville have told me they did a retest after sealing cracks in their basement floor, expecting lower numbers. Sometimes they went down, but other times the levels stayed high because the main entry point was not the cracks, it was the sump pump pit or the gap around the sewer line.

Changes That Can Affect Radon Levels

Several things can cause your home's radon levels to change over time. Here are a few that I have seen firsthand:

• Major renovations: Adding a new foundation, digging a basement, or even finishing a basement can alter how radon enters the home. Construction can open new pathways or seal old ones.
• Changes in the soil: Tree roots, erosion, or nearby construction can shift the soil around your foundation, creating new routes for radon to travel.
• Weather patterns: Prolonged rain, snow cover, or extreme cold can increase the pressure difference between your home and the ground, pulling more radon inside.
• Heating and cooling habits: Running a furnace or air conditioner changes indoor air pressure. Tighter homes with less natural ventilation tend to have higher radon levels.
• Age of the home: Settling, new cracks, and deteriorating seals can all develop over time, even in well-built homes.

A radon retest helps you catch these changes before they become a health concern. I have worked with families in Collinsville who had a radon mitigation system installed years ago. They assumed the system was still working perfectly. A retest showed that the radon fan system had failed silently, and levels had crept back up to 5.3 pCi/L. The fix was simple, replace the fan, but they would not have known without retesting.

The Right Time to Retest

So when should you schedule a radon retest? The U.S. EPA radon guide suggests retesting every two years, or after any significant change to your home's structure or HVAC system. I would add that if you have a radon mitigation system like sub-slab depressurization or soil suction radon reduction, you should test at least once a year to make sure it is still performing. These systems have moving parts, and fans can wear out or become less efficient over time.

If you are buying or selling a home, a radon retest is essential. Many buyers in O'Fallon IL request a new test even if the seller has a recent report. Lenders and real estate agents often want a test that is less than 12 months old. A fresh test gives everyone peace of mind and can prevent surprises at the closing table.

I also recommend a retest if you have recently installed radon-resistant new construction features. While these features are designed to reduce radon entry, they are not foolproof. A post-construction test and then a retest after a year will tell you if the measures are working as intended. In some cases, additional steps like sealing the slab or adding a passive vent may be needed.

Choosing the Right Test Method for a Retest

Not all tests are equal, and the method you choose for a retest matters. For a reliable comparison, try to use the same type of detector as your original test. If you used a short-term radon test the first time, use a short-term test again and test under similar conditions. That way, you are comparing apples to apples. But if you want a more accurate long-term picture, switch to an alpha track detector or a continuous radon monitor for your retest. These devices are less affected by short-term spikes and give a truer average.

E-PERM electrets are another solid option. They are easy to deploy and give a reading that integrates over the test period. I have used them in many homes in Belleville and Edwardsville, and they perform well as long as you follow the instructions carefully. Place the detector in the lowest lived-in level of the home, away from drafts, windows, and exterior walls. Keep doors and windows closed as much as possible during the test period, except for normal entry and exit.

If you hire a professional like Air Sense Environmental, they will typically use a continuous radon monitor, which records readings hour by hour. This gives a detailed picture and can identify patterns, such as spikes during certain weather conditions. That kind of data is invaluable for deciding whether you need radon mitigation or if your current system is working properly.

What to Do After a Retest

If your radon retest shows levels below 2 pCi/L, you are in a good spot. No action is needed, but keep it on your calendar for another test in two years. If levels are between 2 and 4 pCi/L, consider taking steps to reduce entry, such as sealing cracks and improving ventilation. Many homeowners in O'Fallon IL have found that simple measures like these can bring levels down further.

If your retest shows levels at or above 4 pCi/L, it is time to act. Radon mitigation is the next step. Common methods include sub-slab depressurization, which pulls radon from beneath the foundation and vents it above the roofline, or soil suction radon reduction, which works similarly. A radon fan system is often the core of these setups. In some homes, a combination of sealing and active ventilation is needed. The goal is to bring indoor air quality back to a safe range.

I have seen homes in Collinsville where a radon mitigation system brought levels from 8.4 pCi/L down to 1.1 pCi/L. That kind of improvement is life-changing for the families living there. But the story does not end there. They now schedule a radon retest every year to make sure the system is still doing its job. That is the mindset that keeps a home safe over the long term.

Final Thoughts on Radon Retesting

Radon is a silent hazard, but it is one you can manage. Testing once gives you a starting point. A radon retest gives you a follow-up view that accounts for the inevitable changes your home goes through. Whether you live in Belleville, Edwardsville, O'Fallon IL, or Collinsville, the ground beneath your home is always shifting, and your indoor environment shifts with it. Make retesting a regular habit. Your family's health depends on knowing what is in the air you breathe every day.