Radon is a radioactive gas that forms in the ground and can seep into homes through cracks in floors, walls, and foundations. Because it is invisible and has no smell, the only practical way to know whether your home has elevated levels is to test.

Illinois’ weather and housing stock—ranging from basements to slab-on-grade homes—mean radon pathways can vary widely even between nearby properties. That’s why experts recommend testing at the address, not relying on neighborhood averages.

When should you test in an Illinois home?

If you haven’t tested before, schedule a test as soon as possible. You should also retest if you move, finish a basement, seal major openings, install a new HVAC system, or make other structural changes that could alter airflow and pressure.

For many homes, radon testing is most informative during typical living conditions. Use the instructions from your testing kit, but avoid strategies that intentionally change normal ventilation patterns unless the kit guidance specifically recommends it.

How to test for radon

Radon testing typically uses either short-term or long-term measurements. Short-term tests can provide a timely snapshot, while long-term tests are better suited for estimating your average exposure over time.

When choosing a kit, look for products that are appropriate for the testing duration and that clearly explain how to place the device in the lowest lived-in level of the home (often a basement). Follow placement instructions carefully, including where to mount the device and how to handle the test during the measurement period.

• Place the detector according to kit directions, usually in the lowest frequently used level.
• Keep the device in that area and avoid moving it during the test window.
• After the test, return it promptly using the kit’s prepaid instructions.
• Use a qualified service if you prefer a guided process.

Because radon levels can fluctuate, testing won’t be perfectly predictive for a single day. However, a properly conducted test is the best starting point for decision-making.

How to interpret results and when to act

Radon levels are commonly reported in picocuries per liter (pCi/L). National public health guidance generally considers 4.0 pCi/L as a key action threshold, with higher levels indicating greater risk.

If your test result is at or above 4.0 pCi/L, the usual next step is to confirm with additional testing or move directly to mitigation planning, depending on the test type and your testing provider’s guidance. If you receive a result close to that threshold, many homeowners choose follow-up testing to better understand typical levels.

Time matters because radon exposure is tied to long-term accumulation. While no single reading captures your entire year, repeating measurements can help determine whether risk is persistent.

What mitigation usually involves

Mitigation typically aims to prevent radon from entering the home or to reduce indoor concentrations by improving pressure control. For many basements and slab foundations, sub-slab depressurization is a common approach, using a vent pipe and fan system to route radon gas away from living spaces.

Other methods may include sealing specific entry points alongside pressure-based techniques. In general, the most effective solutions are designed based on your home’s structure and pressure conditions rather than relying on generic fixes.

Choosing a professional and next steps

If you decide to mitigate, select a qualified radon mitigation professional and ask what system will be installed, how it fits your foundation type, and how results will be verified after the work is completed. Many homeowners benefit from post-mitigation testing to confirm that indoor levels have dropped.

Even after mitigation, periodic checks are a prudent way to ensure performance remains stable, especially if major renovations occur. Testing and verification together form a practical cycle: measure, act, and confirm.

For Illinois residents looking for a straightforward path, the key is simple: test your home, interpret results using established thresholds, and don’t delay action if levels are elevated.