Radon Testing
Professional Radon Testing in Fort Collins and Northern Colorado
A radon test is a measurement of a building during a defined period - not a permanent label for the property. Radon levels change with weather, soil moisture, operation of the building, ventilation, pressure, renovations, and season. The goal is to use an approved device, place it correctly, maintain the required building conditions, document the test, and interpret the result in context.
Drennen provides licensed radon measurement for homeowners, real estate transactions, post-mitigation verification, property managers, schools, multifamily buildings, and commercial facilities. Our measurement department operates an in-house testing and reporting workflow under a Colorado-licensed Radon Measurement Professional.
Professional radon measurement is a regulated activity in Colorado. Verify that the responsible individual holds an active Colorado Radon Measurement Professional license. A mitigation license alone does not authorize professional measurement.
Colorado homeowners can learn more about radon risks, testing recommendations, and mitigation guidance through the Colorado Department of Public Health and Environment radon guidance and the EPA radon information.
Which Test Is Right for You?
Homeowner Screening Test
A short-term test can help determine whether the home needs additional measurement or mitigation. CDPHE identifies short-term testing periods of approximately 48 to 120 hours, depending on the approved device and protocol.
Real Estate Transaction Test
The test is placed in the lowest area that could be occupied, follows closed-building conditions, documents the transaction period, and should be conducted by a licensed measurement professional using an approved professional device.
Post-Mitigation Test
Testing after installation documents whether the new system achieved the initial performance target. The timing and method should follow the applicable standard and any transaction requirements.
Long-Term Test
A long-term test runs more than 90 days and better represents annual exposure because it captures more seasonal and operating variation.
Large-Building Test
Schools, multifamily buildings, childcare facilities, offices, and mixed-use buildings require a sampling plan, device tracking, quality-control devices, floor-plan coordination, and reporting appropriate to the building type.
Where Should a Radon Test Be Placed?
For an owner evaluating normal exposure, EPA and CDPHE guidance generally focuses on the lowest lived-in level. During a real estate transaction, the test is generally placed in the lowest area that could be used as living space, including an unfinished basement that could later be occupied.
- Place the device in a normal breathing zone and a location where it will not be disturbed.
- Avoid exterior walls, windows, doors, direct sunlight, high heat, strong drafts, and supply or return vents.
- Do not place the device on stone surfaces or where humidity, water, or household activity can compromise the measurement.
- Document start and stop date and time, device serial number, location, building conditions, weather concerns, and any observed interference.
Closed-Building Conditions
Short-term tests used for decision-making require closed-building conditions before and during testing. Exterior doors and windows remain closed except for normal entry and exit. Whole-house fans or other equipment that brings substantial outdoor air into the building should not be operated unless the protocol allows it. Normal heating and cooling can continue.
Opening windows, moving a device, placing a fan next to the test, or changing building operation can invalidate or distort a result. A professional report should identify observed deviations or suspected interference.
Drennen Testing Methods and Reporting
Drennen uses approved measurement devices selected for the project. Our large-building and laboratory workflow has included electret ion chamber devices, device voltage readings before and after exposure, chain-of-custody records, duplicate devices, blanks, and written quality-control documentation. Real estate and residential methods may also use other approved devices as appropriate.
- Test placement and retrieval under the licensed measurement program
- Device identification and chain-of-custody documentation
- Review of test conditions and potential interference
- Result reported in picocuries per liter, or pCi/L
- Plain-language recommendations based on the result and the reason for testing
- Quality-assurance procedures for projects that require duplicates, blanks, or other controls
Understanding the Result
Below 2.0 pCi/L
Lower risk than higher concentrations, but not zero risk. Continue periodic testing, especially after building changes.
2.0 to 3.9 pCi/L
Below the EPA action level but still above typical outdoor concentrations. Consider a long-term test, additional measurement, or mitigation based on occupancy, risk tolerance, transaction needs, and professional guidance.
4.0 pCi/L or Higher
EPA and Colorado guidance recommend taking action to reduce the level. Confirmatory testing may be appropriate in some non-transaction situations; transaction deadlines may require prompt professional interpretation.
Very High Result
Do not panic, but address it promptly. Verify the test conditions and consult a licensed professional about mitigation. Most radon problems can be reduced with a properly designed system.
When to Retest
- At least every two years, even when an active mitigation system is installed
- After fan replacement, system repair, modification, or a failed warning device
- After foundation work, a new addition, finishing a basement, or creating a new occupied ground-contact area
- After significant HVAC, ventilation, energy-efficiency, or weatherization changes
- When buying or selling the property
- After major ground disturbance, flooding, drainage changes, or new large cracks
Frequently Asked Questions
Schedule a Valid Radon Test
Tell us why you are testing, the property type, lowest foundation level, whether a mitigation system exists, access details, and any closing or inspection deadline. We will recommend an appropriate measurement approach.
Schedule a Radon TestThis page is general educational information. Test selection, placement, quality control, and interpretation must follow the current Colorado rules and the applicable ANSI/AARST standard for the building and purpose.
Drennen Custom Contracting | Fort Collins, CO | 970-482-9100 | [email protected]