Why Post Mitigation Testing Is Essential
Post mitigation testing is the critical final step in the radon mitigation process. After a radon reduction system is installed in your home, a follow-up test is the only way to confirm that the system is actually working and that radon levels have been reduced to safe concentrations. The EPA strongly recommends that every home with a newly installed mitigation system undergo post-mitigation testing to verify results, and we include this testing as a standard part of every installation we perform in Billings and across Yellowstone County.
Without post mitigation testing, you have no objective verification that your system is performing as designed. While visual indicators like the U-tube manometer confirm that the fan is generating suction, they do not tell you what your actual indoor radon concentration is. Only a properly conducted radon test can provide that measurement. As a licensed and insured radon mitigation company, we consider post mitigation testing a non-negotiable part of protecting your family's health.
What the EPA Recommends
The EPA recommends that post mitigation testing be conducted no sooner than 24 hours after system installation and ideally within 30 days. This waiting period allows the system to establish stable operating conditions and gives soil gas pathways time to equilibrate under the new pressure dynamics created by the mitigation system. Testing too soon can produce unreliable results that do not reflect the system's long-term performance.
The EPA further recommends retesting your home every two years, even after a successful post mitigation test, to ensure that radon levels remain low over time. Changes in your home's structure, foundation settling, soil conditions, or system component wear can all affect radon levels. Periodic retesting provides ongoing assurance that your protection is intact. We offer affordable retest services for all homeowners in the Billings area, whether or not we installed your original system.
Our Post Mitigation Testing Process
Our post mitigation testing follows the same rigorous EPA-approved protocols we use for all radon testing. We deploy a calibrated continuous radon monitor (CRM) in the lowest livable area of your home, typically the same location where the initial pre-mitigation test was conducted. This allows for a direct comparison of before-and-after results that clearly demonstrates the effectiveness of your mitigation system.
The test runs for a minimum of 48 hours under closed-house conditions, with hourly readings recorded throughout the test period. Once the test is complete, we retrieve the monitor, analyze the data, and provide you with a detailed written report that includes:
- Your average post-mitigation radon concentration in pCi/L
- Hourly radon level readings showing concentration patterns over the test period
- A comparison to your pre-mitigation radon levels to demonstrate system effectiveness
- Confirmation of whether your levels meet the EPA action level threshold of 4 pCi/L
- Recommendations for ongoing monitoring and future retesting
Understanding Your Post Mitigation Results
After a successful mitigation system installation, most homes in Billings see radon levels drop dramatically. It is common for post-mitigation results to show levels between 0.5 and 2.0 pCi/L — well below the EPA action level of 4 pCi/L and often a reduction of 90% or more from pre-mitigation concentrations. These results confirm that your system is working effectively and that your home's air is safe.
If your post mitigation test shows radon levels at or above 4 pCi/L, it indicates that the system needs adjustment. This is uncommon but can happen in homes with very high initial radon levels, complex foundation configurations, or unusual soil conditions. In these cases, our guarantee applies: we return to your home, diagnose the issue, and make the necessary modifications to bring your levels below the action threshold at no additional cost to you.
Results between 2 and 4 pCi/L are considered acceptable by EPA standards, though they represent a range where the EPA suggests that further reduction may be beneficial. We can discuss options for system optimization if your results fall in this range and you would like to pursue even lower radon concentrations.
Post Mitigation Testing for Real Estate Transactions
If you are selling a home in Billings that has a radon mitigation system, a current post mitigation test report is often required or strongly preferred by buyers and their lenders. Providing verified test results demonstrates that your system is operational and effective, which builds buyer confidence and helps prevent delays in the closing process. We can provide certified post mitigation testing with fast turnaround to meet real estate transaction timelines.
For home buyers, we recommend requesting to see the most recent post mitigation test results for any property with an existing radon system. If the test is more than two years old or if results are unavailable, scheduling a new post mitigation test is a prudent step before completing your purchase. Our licensed and insured technicians can conduct testing quickly and provide you with the documentation you need to make an informed decision.
Ongoing Radon Monitoring After Mitigation
Beyond the initial post mitigation test, we recommend several simple practices to ensure your radon protection remains effective over time. Check your U-tube manometer monthly to verify your system is maintaining proper suction. Schedule a professional retest every two years to confirm radon levels remain safely below the EPA action level. If you make any structural changes to your home, particularly to the foundation or basement, consider retesting afterward to ensure your system is still performing optimally. Our team is always available to answer questions or schedule a follow-up test for any homeowner in the Billings area.