What Happens After a Failed Radon Test?
By Daniel SmokeDirector of Operations
A radon test result at or above 4 pCi/L is actionable information, not a cause for alarm. Millions of U.S. homes have elevated radon levels, and the vast majority can be mitigated effectively. Understanding the process from initial result to mitigation completion helps you move forward efficiently.
Confirm the Result
A single short-term test result between 4 and 8 pCi/L should generally be confirmed with a follow-up test before committing to mitigation. This is because short-term tests can be affected by temporary conditions that do not reflect typical long-term exposure. These include unusual weather, changes in HVAC operation, or other transient factors. A second short-term test (which can be averaged with the first) or a long-term test provides more confidence. For results above 8 pCi/L, or when a real estate transaction is pending, proceeding directly to mitigation is often the practical choice.
Hire a Certified Mitigation Contractor
Radon mitigation should be performed by a contractor certified by the National Radon Proficiency Program (NRPP) or the National Radon Safety Board (NRSB). These programs require training, testing, and continuing education. Certified contractors are required to follow the EPA's mitigation standards (EPA/625/R-17/001a) and provide written documentation of the work performed and post-mitigation test results. Request certification documentation before hiring any mitigation contractor.
The Mitigation Process
Sub-slab depressurization (SSD) is the standard and most effective mitigation method for homes with basements or slab-on-grade construction. The contractor drills one or more suction holes through the slab and inserts a PVC pipe connected to a continuously running fan. The pipe is then routed to discharge above the roofline.
The fan creates negative pressure below the slab, drawing radon-laden soil gas out before it can enter the home. Installation typically takes four to eight hours. Crawlspace homes use a variation called sub-membrane depressurization, where a barrier is installed over exposed soil.
Post-Mitigation Testing
After the mitigation system is installed, a post-mitigation test is required to confirm the radon level has been adequately reduced. Most certified contractors conduct this test themselves, but an independent third-party test provides additional assurance. Post-mitigation tests are typically short-term (48-hour) charcoal tests or electronic monitor readings. The goal is to achieve levels below 4 pCi/L, with below 2 pCi/L as the recommended target. If results remain elevated, the contractor should assess the system and make adjustments at no additional charge.
Ongoing Monitoring
After successful mitigation, continued monitoring ensures the system remains effective over time. The EPA recommends testing every two years. System performance indicators, audible or visible diagnostic devices that show whether the fan is operating and pressure is being maintained, should be checked periodically. Most mitigation fans are rated for 20 years of continuous operation. A significant increase in radon levels on a follow-up test may indicate the fan has failed or the system needs service.
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