Radon Basics

Radon Risk and Testing Basics in Northern Colorado

Radon is a naturally occurring radioactive gas produced as uranium breaks down in soil and rock. It has no color, odor, or taste. It can enter through foundation cracks, construction joints, sumps, drains, penetrations, crawl spaces, and other soil-connected openings.

Radon is a proven cause of lung cancer. CDPHE reported in January 2026 that approximately half of Colorado homes exceed the EPA action level of 4.0 pCi/L. A map, home age, foundation type, neighbor result, or existing radon pipe cannot tell you the level in your property. Test it.

Schedule a Radon Test Request a Test Kit or Professional Test

Why Colorado Has a Radon Problem

Colorado geology contains uranium-bearing rock and soil, and buildings can draw soil gas inward through pressure differences. Any home can test high: new or old, basement or slab, tightly built or drafty, expensive or modest, with or without a visible passive pipe.

Understanding the Number

Below 2.0 pCi/L

Generally a lower result, but no radon concentration is completely risk-free. Continue periodic testing and retest after significant changes.

2.0 to 3.9 pCi/L

Below the EPA action level, but EPA recommends considering reduction in this range. A long-term test can help estimate annual average when time allows.

4.0 pCi/L or Higher

EPA recommends mitigation. Confirm the measurement context and obtain proposals from licensed Colorado Radon Mitigation Professionals.

Very High Result

Do not panic, but do not ignore it. Contact a licensed measurement or mitigation professional promptly to review the test and the appropriate next step.

The 4.0 pCi/L action level is not a safety line. Risk generally increases with concentration and exposure duration.

Short-Term and Long-Term Testing

Short-Term Test

Typically runs 48 to 120 hours depending on the approved device. It is useful for real estate deadlines, initial screening, and post-mitigation verification when protocol conditions are maintained.

Long-Term Test

Runs 91 days to one year and is performed under normal living conditions. It better represents seasonal and daily variation and the annual average.

Professional Test

A licensed measurement program selects an approved device, location, timing, controls, quality assurance, and report appropriate to the purpose.

Where to Test

For ordinary homeowner decisions, EPA recommends the lowest living area. For a real estate transaction, test the lowest area that could be converted to living space, such as an unfinished basement. Keep the device away from exterior doors, windows, walls, fans, vents, direct sunlight, heat, humidity, and places where it can be disturbed.

Closed-Building Conditions for Short-Term Tests

Close windows and exterior doors for the required period before and during testing, except normal entry and exit
Operate normal heating or cooling but avoid unusual whole-house ventilation
Do not move, cover, unplug, or place a fan near the device
Record start and stop dates and times accurately
Tell the professional about construction, weather, HVAC changes, or suspected interference

What to Do After the Result

1
Below the action level
Keep the report and retest periodically, especially after finishing the basement, altering ventilation, foundation work, or a real estate transaction.
2
At or above the action level
Contact a licensed mitigation professional for a property-specific proposal. Most homes can be reduced with active soil depressurization.
3
After mitigation
Complete the post-mitigation test, keep the system records, look at the warning device regularly, and retest at least every two years.

Testing Myths

My neighbor was low, so I am low

False. Radon pathways and building pressures can change from one foundation to the next.

A new home is safe

False. New homes can test high. A passive rough-in is not a test result.

Granite countertops are the main problem

Usually false. Soil gas is the dominant source in most homes.

Sealing every crack solves radon

False. Sealing supports a depressurization system but is rarely effective as the sole strategy.

The manometer tells me my radon level

False. It indicates system pressure, not indoor concentration.

Frequently Asked Questions

Test the Property, Not the ZIP Code

Drennen can help select a test, explain the result, evaluate an existing system, and prepare a licensed mitigation plan when needed.

Schedule a Radon Test

Health information is educational and not medical advice. Testing and mitigation decisions should use current EPA, CDPHE, DORA, and licensed-professional guidance.

Drennen Custom Contracting | Fort Collins, Loveland, Windsor & Northern Colorado | 970-482-9100 | [email protected]