Most homeowners think radon testing is a one-and-done task, often performed only during real estate transactions. But in high-risk areas like Colorado—where radon levels frequently exceed safe limits—regular testing is a critical part of long-term home health and safety.
So how often should you test radon in your Colorado home? The answer depends on several key factors, including:
• The age of your last test
• Whether you’ve had mitigation installed
• Seasonal changes and climate conditions
• Renovations or structural changes to your home
This guide breaks down expert recommendations and best practices so you can stay ahead of this invisible but serious threat.
This guide breaks down expert recommendations and best practices so you can stay ahead of this invisible but serious threat.
What Is Radon and Why Is It Dangerous?
Radon is a naturally occurring radioactive gas that forms when uranium in soil and rock breaks down. It seeps into homes through:
• Cracks in the foundation
• Sump pits
• Crawl spaces
• Utility openings
The danger? Radon is the second leading cause of lung cancer in the United States, responsible for over 21,000 deaths annually, according to the EPA.
You can’t see it, smell it, or taste it. That’s why radon testing is the only way to know if your home is affected.
Why Is Radon Testing Especially Important in Colorado?
Why Is Radon Testing Especially Important in Colorado?
Colorado ranks among the top radon zones in the country due to its uranium-rich soil and mountainous terrain. The Colorado Department of Public Health and Environment (CDPHE) reports that:
- Over 50% of homes tested in Colorado exceed the EPA action level of 4.0 picocuries per liter (pCi/L)
- Some counties report levels as high as 10–20 pCi/L on average
Additionally, homes in Colorado are often built to retain heat, which means less ventilation—a key contributor to elevated indoor radon levels.
So, How Often Should You Test Radon in Colorado?
The EPA and CDPHE recommend testing every 2 years, but this can vary depending on your home’s condition and history.
Here’s a breakdown:
| Situation | Testing Frequency |
|---|---|
| Never tested before | Test immediately |
| Last test was over 2 years ago | Retest every 2 years |
| Recent structural renovations | Test after renovation is complete |
| Installed or updated mitigation system | Test within 24 hours, then every 2 years |
| Buying or selling a home | Test before listing or during due diligence |
| Not living in the home year-round | Test seasonally (especially in winter) |
| Own a rental property | Test between tenants or every lease renewal |
Why 2 Years? Understanding Radon Variability
Radon levels can change over time, even in the same house, due to:
• Soil moisture and freeze-thaw cycles
• Barometric pressure
• HVAC system updates
• Foundation shifting or settling
• Installation of insulation, windows, or air sealing
That’s why a home that once tested at 2.5 pCi/L might now read 5.8 pCi/L—well above the EPA’s action level.
The Best Time of Year to Test: Winter Months
Radon levels are typically highest in the winter, when homes are sealed against the cold and airflow is reduced.
During winter:
- Windows and doors remain closed
- Heating systems promote radon suction from the soil
- Cold weather increases stack effect (drawing more radon in)
Pro Tip: If you’re only going to test once, do it in the coldest months (December to February) for the most accurate reading of peak exposure.
How Radon Retesting Works
Most certified radon professionals use Continuous Radon Monitors (CRMs) for short-term testing (48–96 hours). These provide hourly readings and tamper-proof data.
If you’re testing regularly:
- Schedule the test with a certified technician
- Follow closed-house conditions (12 hours prior and during the test)
- Get results and recommendations within 1–3 days
If previous levels were near or above 4.0 pCi/L, consider long-term testing using alpha track devices, which measure over 90+ days.
What to Do if Retest Results Are High
If radon retesting reveals levels above 4.0 pCi/L:
• Do not panic—mitigation systems can quickly lower levels
• Schedule a consultation for radon mitigation
• Consider additional sealing or crawl space encapsulation
• Continue regular testing after mitigation to ensure system performance
Learn more about Radon Mitigation Services
Do you have a Radon Mitigation System? Keep Testing!
Many homeowners believe that once they’ve installed a radon mitigation system, testing is no longer necessary.
False! All systems require periodic monitoring to:
- Confirm proper operation
- Ensure fan functionality
- Check for pressure or airflow drops
- Track long-term radon exposure
Post-Mitigation Retesting Schedule:
• Within 24–72 hours of installation
• Annually for the first 2 years
• Every 2 years thereafter
Testing After Renovations or Repairs
If you’ve made any of the following changes, you should test your home for radon as soon as the work is complete:
• Finished a basement
• Installed new HVAC or ductwork
• Added insulation or sealed cracks
• Converted crawl space to living space
• Installed energy-efficient windows
These modifications can change your home’s airflow, potentially increasing radon accumulation.
Testing Rental Properties or Multi-Unit Homes
If you own or manage rental properties in Colorado:
- Test each unit or floor independently
- Retest between tenants
- Maintain a radon log for liability and transparency
Although not currently mandated by Colorado law, radon disclosure is highly recommended for rental agreements and lease renewals.
Should You Use a DIY Radon Test Kit?
DIY kits from hardware stores or online retailers are widely available. While they can be useful for screening, they come with risks:
• User error (wrong placement, handling, or timing)
• Tampered conditions (open windows, HVAC changes)
• Not accepted in real estate or legal settings
For official or reliable results, always hire a certified professional—especially in high-risk areas like Colorado.
Choosing the Right Testing Professional in Colorado
Make sure your radon tester is:
• NRPP or NRSB certified
• Uses calibrated, tamper-proof equipment
• Provides a written report
• Offers guidance on next steps if levels are high
Looking for a certified and local expert? At Colorado Radon Mitigation, our NRPP-certified team provides accurate, reliable, and fast radon testing and retesting services tailored for Colorado’s unique needs.
Final Thoughts: Stay Proactive with Your Home’s Radon Health
Radon isn’t a one-time concern—it’s an ongoing home health issue. Just because your home tested low five years ago doesn’t mean it’s still safe today.
To keep your household protected:
- Mark your calendar for biennial testing
- Schedule a test after any renovations
- Monitor existing mitigation systems regularly
- Choose a certified professional for reliable results
Need Help with Radon Testing or Retesting?
If it’s been more than 2 years since your last radon test—or if you’ve never tested—now is the time to act.
At Colorado Radon Mitigation, we offer:
- NRPP-certified radon testing
- Pre- and post-mitigation monitoring
- Long-term alpha track test solutions
- Transparent, affordable pricing
📞 Call us today at (970-340-8744) or
👉 Contact us for a free consultation
Frequently Asked Questions
1. How often should I test my Colorado home for radon?
You should test your home for radon every 2 years, or immediately after major renovations, HVAC changes, or if a mitigation system has been installed. Seasonal testing, especially in winter, is also recommended for part-time residents.
2. When is the best time of year to test radon in Colorado?
Winter is the ideal time to test because homes are sealed, increasing the potential for radon buildup. Testing during this season provides the most accurate assessment of your highest possible radon exposure.
3. Do I need to test radon again if I already have a mitigation system?
Yes. Even with a mitigation system, annual testing for the first two years and every two years thereafter is recommended to ensure the system is functioning correctly and radon levels remain safe.
4. Should I retest radon after remodeling my home?
Absolutely. Structural changes—like finishing up a basement, updating HVAC, or installing insulation—can alter airflow and potentially increase radon levels. Always test after renovations are complete.
5. Are DIY radon test kits reliable in Colorado?
While DIY kits can be useful for preliminary screening, they are prone to error and are not accepted in real estate transactions. For accurate, reliable, and legally recognized results, hire an NRPP-certified radon testing professional.