How Often Should You Test for Radon After Installing a Mitigation System?

So, you’ve taken the important step of installing a radon mitigation system in your home. You’ve got the PVC pipes running up, the fan hums gently in the background, and you can finally breathe a sigh of relief knowing your family is protected from this invisible, odorless gas.
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But now comes a question we hear constantly from homeowners here in El Paso County: "Once the system is in, am I done testing forever?"

The short answer is no. While an active radon mitigation system is incredibly effective—often dropping indoor radon levels by 50% to 90%—it is not a set-it-and-forget-it appliance. To ensure your air stays safe, you must test on a regular schedule.
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Below is a breakdown of exactly when and how often you should test your home’s radon levels after mitigation.

1. The Post-Installation Test (24 Hours to 30 Days)

​The very first test must happen almost immediately after the system is installed.
Once we finish installing a mitigation system, we allow it to run continuously for at least 24 hours to establish a steady state of negative pressure beneath your home’s foundation.

• Why it matters: This initial post-mitigation test is your baseline. It proves that the system was installed correctly, that the fan is sized right for your home’s footprint, and that radon levels have dropped below the EPA's action level of 4.0 pCi/L (and ideally down closer to outdoor levels of around 0.4 pCi/L).
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• Who does it: Usually, the mitigation company will set up a continuous radon monitor for a short-term 48-hour test to verify their work.

2. The Routine Check: Every Two Years

According to guidelines from the Environmental Protection Agency (EPA) and the American Association of Radon Scientists and Technologists (AARST), you should test your mitigated home at least once every two years.

​Even if your fan is running smoothly, several factors can cause your radon levels to fluctuate over time:

• Ground Settling & Soil Shifting: Here in the Colorado Springs area, our unique geology (including the decomposed granite around the Pikes Peak region) is constantly shifting. New cracks can form in your concrete slab, or old sealed cracks can reopen, creating new pathways for radon to bypass the system.
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• Fan Wear and Tear: Radon fans run 24/7, 365 days a year. While high-quality fans are built to last, their bearings eventually wear out, causing a drop in suction power before the fan dies completely.
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• Seasonal Temperature Swings: Colorado Springs experiences massive temperature swings. In the winter, we keep our homes sealed tight, which creates a "stack effect" (warm air rising pulls cold air and radon up from the soil). Testing every two years at different times of the year helps capture these seasonal variances.

3. Special Scenarios: When to Test Sooner

You shouldn't always wait for the two-year mark. If any of the following occur, you should place a test kit in your home immediately:

• Major Remodeling or Structural Work- If you finish your basement, add an addition, or cut into the concrete slab to add plumbing, you alter the air pressure dynamics of your home. Any disruption to the soil or foundation slab requires a follow-up test to ensure the system is still pulling radon effectively from beneath the entire footprint.
  
  
• HVAC Changes- Replacing a furnace, installing a central air conditioning unit, or adding a whole-house ventilation system changes how air moves inside your home. These pressure shifts can sometimes draw radon out of the ground in areas where the mitigation system's suction doesn't reach.
• Earthquakes or Blasting - While rare, heavy seismic activity, nearby construction blasting, or severe soil erosion can shift the earth beneath your home, altering the sub-slab vacuum chamber your system relies on.​

Between Tests: Keep an Eye on the Manometer

You don't have to guess if your system is running. Every active radon system has a small, clear U-shaped tube filled with red or blue liquid attached to the system's suction pipe, usually in the basement or garage. This is called a manometer.​

The manometer measures pressure, not radon levels.
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• If the liquid levels are uneven: Your fan is creating a vacuum, pulling air from under the slab. This is what you want to see.
  
  
• If the liquid levels are perfectly flat (both sides pointing to zero): The fan has lost power, failed, or a pipe is fully blocked. Your system is not working.
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Note: While checking your manometer weekly is a great habit, it only tells you that the fan is spinning—it cannot tell you if a new crack has opened up elsewhere in the basement. Only an actual radon test can verify the air quality.

Protect Your Peace of Mind

Maintaining a radon-free home is all about vigilance. If it’s been more than two years since your last radon test, or if you’ve recently completed some home renovations, it's time to test.
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Testing is simple, affordable, and the only reliable way to ensure the air your family breathes is safe. If you're in the Colorado Springs area and need professional testing, a system health check, or a fan replacement, feel free to reach out to our team. 

Relater Article:

Reasons Why Every Colorado Homeowner Should Test for Radon