How to Check for Radon in Your Home: Overview & Results
Searching for “how to check for radon in your home” returns a mix of test-kit ads, professional-service pitches, and EPA guidance documents. The information overlap obscures the basic structure of the decision: which test type to run, how to interpret the resulting pCi/L value against EPA thresholds, and what action that value should drive. This guide compresses the workflow into a single overview, with particular attention to results interpretation and Colorado Front Range Zone 1 risk context. The article reflects EPA, CDC, and CDPHE guidance current as of 2026; consult a NRPP-certified pro for transaction or post-mitigation testing.
The three things checking for radon involves
“Checking for radon” is shorthand for three sequential activities: selecting and running a test, interpreting the resulting concentration value, and deciding what action (if any) to take. Each step has well-defined options and standard recommendations. Skipping or shortcutting any step undermines the value of the others.
Step 1: choose a test method
Three main test categories cover most homeowner situations.
DIY short-term kits (2-7 days)
Charcoal canister or electret ion chamber kits cost $15-$50 including lab analysis. Adequate for initial screening when closed-house conditions are maintained.
DIY long-term alpha-track (90 days to 1 year)
Plastic-film detectors record alpha tracks over weeks to months, producing an annual-average value. Cost $25-$50 including analysis. Better for confirming borderline results and for representing typical exposure.
Professional continuous radon monitor (48+ hours)
NRPP- or NRSB-certified pro brings a calibrated electronic monitor to the home. Hourly logs, digital report, chain-of-custody documentation. Cost $150-$400. Required for real-estate transactions and post-mitigation verification.
Step 2: run the test correctly
Regardless of method, follow the EPA closed-house protocol: 12 hours before the test, close all windows and exterior doors except for normal entry/exit; maintain heating and air conditioning as you normally would; do not operate whole-house or window fans; do not run a fireplace with open damper. These conditions must continue throughout the test period.
Place the device in the lowest level regularly occupied (typically a basement), 20+ inches above the floor, 4+ inches from walls, away from drafts and heat sources. Record exact start and end times. Ship to lab promptly after the exposure period ends.
Step 3: interpret the pCi/L result
Radon concentration is reported in picocuries per liter of air (pCi/L). The EPA action level is 4 pCi/L. CDPHE adopts this threshold for Colorado. The WHO recommends action at 2.7 pCi/L. Result interpretation follows a standard framework.
Below 2 pCi/L
Low risk under current conditions. Retest every 2-5 years or after major renovation. No mitigation needed.
2 to 4 pCi/L
Intermediate range. EPA does not require mitigation but notes that no level of radon is risk-free. Consider a long-term alpha-track for annual average confirmation. Mitigation is optional but reasonable, particularly if you have a basement bedroom or sustained basement occupancy.
4 to 10 pCi/L
Above EPA action level. Confirm with a second short-term test (ideally simultaneously, side-by-side) or upgrade to a professional continuous monitor. If confirmed, proceed with mitigation. Sub-slab depressurization typically costs $1,500-$3,500.
Above 10 pCi/L
Substantially elevated. EPA recommends mitigating promptly without waiting for confirmation. Consider testing other levels of the home and limiting basement occupancy until mitigation completes.
Why a single number can mislead
Short-term tests capture a window of typically 2-7 days. Radon concentration varies daily with weather (barometric pressure, wind), seasonally (higher in heating season), and with occupancy patterns. A single short-term test result can over- or under-state annual average exposure by 50% or more in extreme cases. Two short-term tests run in parallel (or sequentially) reduce uncertainty significantly. A long-term alpha-track produces the most representative value.
Front Range Zone 1 risk context
Most Front Range counties — Denver, Boulder, Jefferson, Adams, Arapahoe, Douglas, El Paso, and adjacent — are EPA Zone 1. Zone 1 designation means the predicted average indoor radon concentration exceeds 4 pCi/L. CDPHE empirical data confirms this: roughly half of tested Front Range homes register above the action level. The driving geology is radium-bearing granitic rock and uranium-enriched sedimentary formations beneath much of the Colorado plateau and the foothills.
In practical terms: if you live on the Front Range, the baseline probability that your home is elevated is approximately 50%. This is far higher than the U.S. average (about 1 in 15). Our hub on radon testing for Front Range homeowners covers regional context in depth.
What to do with the result
Action follows the threshold framework above, but with a few practical considerations.
Confirm before mitigating
A single short-term test above 4 pCi/L should be confirmed by a second test before paying $1,500-$3,500 for mitigation. The second test can be another short-term kit (ideally simultaneously, side-by-side) or a professional continuous radon monitor.
Use a certified contractor
NRPP-certified mitigation contractors install systems that meet EPA Radon Mitigation Standards. Verify certification on the public registry. Get at least two written quotes with comparable scope. Bids should include sub-slab suction-point installation, pipe routing, fan model and warranty, manometer/pressure gauge, sealed sump cover, exhaust termination per RMS, and post-installation testing.
Retest after mitigation
EPA recommends post-mitigation testing 24-30 days after system commissioning. Verify concentration is below 4 pCi/L (ideally below 2 pCi/L). Annual retesting confirms system performance over time. Our cluster on radon system inspection covers post-installation verification in depth.
Real-estate transaction protocols
If you are buying or selling a home, the radon test in the transaction window has different rules. Most contracts and lenders require:
Test performed by a NRPP- or NRSB-certified measurement professional.
Continuous radon monitor for 48 hours minimum.
Closed-house conditions verifiable by the pro.
Tamper-resistant placement or sealed device.
Chain-of-custody documentation and digital report.
DIY tests rarely satisfy these requirements. Plan transaction testing as a professional engagement separate from any earlier DIY screening.
Common testing errors
Watch for these recurring mistakes:
Opening windows during the test (invalidates closed-house protocol).
Placing the kit in a closet, kitchen, or near drafts.
Running the test for too short a period (less than 48 hours for short-term kits).
Forgetting to ship the kit promptly after the exposure window.
Trusting a single test for mitigation decisions without confirmation.
Testing during atypical conditions (vacation away, severe weather, HVAC change).
When to retest
Retesting is recommended after: finishing a basement (changes airflow and pressure dynamics), replacing the HVAC system, replacing windows or weatherstripping (tightens the envelope), major foundation work, 2-5 years under stable conditions, and any time post-mitigation results trend upward. Long-term continuous monitors with display screens make ongoing retesting essentially automatic.
Health framing
Radon exposure causes lung cancer through cumulative inhalation of decay products over decades. There are no acute symptoms — a brief stay in a high-radon home does not warrant medical intervention. Sustained occupancy in a high-radon home over many years substantially increases lifetime lung cancer risk, especially in combination with smoking. CDC estimates roughly 21,000 U.S. lung cancer deaths annually are attributable to radon. The most actionable response is testing, mitigating if elevated, and quitting smoking if you smoke. Consult your physician for symptom evaluation or cancer-screening discussion.
Ongoing self-monitoring
For homeowners who have tested and want continuous visibility, a consumer continuous radon monitor ($150-$300 one-time purchase) provides hourly readings on a display. The device is not a substitute for transaction-grade or post-mitigation testing but provides excellent ongoing surveillance after mitigation. Our walkthrough of how to check radon levels and interpret pCi/L covers the ongoing monitoring approach in depth.
What checking for radon does not require
You do not need: a geological survey, foundation inspection, indoor air quality consultant, structural engineer, or environmental hazard assessment to check for radon. A single test kit or professional measurement is sufficient. Visual inspection, smell, and other indirect indicators do not detect radon and are not part of the standard checking workflow.
Bottom line on checking for radon
Checking for radon involves three steps: running an appropriate test under closed-house conditions, interpreting the pCi/L value against the EPA 4 action level, and deciding action based on the threshold framework. For initial screening, a DIY short-term kit is adequate. For high-stakes decisions, hire a NRPP-certified pro. For Front Range homeowners in EPA Zone 1, testing is the baseline expectation — and the probability of finding elevated concentration is approximately 50%.
How units (pCi/L vs Bq/m3) work
Radon concentration is reported in two unit systems. The U.S. standard is picocuries per liter (pCi/L). The international standard is becquerels per cubic meter (Bq/m3). The conversion is 1 pCi/L = 37 Bq/m3. EPA’s 4 pCi/L action level equals 148 Bq/m3. WHO’s 100 Bq/m3 recommendation equals about 2.7 pCi/L. International test reports may use Bq/m3; verify which unit applies when reading any documentation. Most U.S. labs report in pCi/L; some report both for clarity.
What checking returns depending on test type
Different test types deliver different result formats.
Short-term DIY kit
Single average concentration value over the exposure period in pCi/L. Lab certificate with collection dates, exposure duration, and result. No hourly logs.
Long-term alpha-track
Single average over the long exposure period. Statistically more representative of annual average than a short-term kit. Lab certificate with start/end dates and analyzed track count.
Continuous radon monitor
Hourly readings over the exposure period plus average, minimum, maximum, and statistical summary. Some monitors export digital logs in CSV or PDF. Patterns in the hourly data reveal HVAC effects and weather influence.
Consumer CRM with phone app
Real-time and historical readings on a smartphone app. Trends over weeks and months. Comparison to EPA threshold and personalized risk estimates.
How school and workplace testing differs from home testing
Schools follow EPA AHERA-derived radon-testing protocols (different from the asbestos AHERA, despite the name overlap) with longer measurement durations and specific placement protocols. Workplace testing follows OSHA general-duty standards plus state-specific requirements; some states (notably Maine and New Jersey) require periodic workplace radon testing. Home testing follows the EPA Citizen’s Guide framework, which is less prescriptive but produces compatible results when closed-house conditions are maintained. The fundamental physics of radon measurement is the same across contexts.
How to handle a high result without panic
Elevated radon is a long-term cancer-risk factor, not an acute hazard. There is no need to evacuate the home, restrict children from basement bedrooms immediately, or call a hazmat team. The appropriate response: confirm with a second test (parallel or sequential), then mitigate with a certified contractor over the following 1-4 weeks. Mitigation lead times on the Front Range typically run 1-3 weeks from contract signing to installation. During the interim period, increase basement ventilation (open windows when weather allows), limit basement-bedroom use if practical, and avoid running fans that depressurize the basement.
How radon mitigation works in practice
Sub-slab depressurization is the standard mitigation. A licensed contractor drills a 4-6 inch suction point through the basement slab into the gravel layer below, installs PVC pipe routed to an exterior fan, mounts the fan above conditioned space, and terminates the exhaust above the roofline. The fan creates negative pressure in the gravel layer that intercepts radon-laden soil gas before it enters the home. Installation typically takes 4-8 hours. Post-installation testing 24-30 days later confirms the system reduces concentration below 4 pCi/L and usually below 2 pCi/L. Annual fan maintenance and 5-year inspections keep the system performing over decades.
References
- EPA Citizen’s Guide to Radon — U.S. Environmental Protection Agency
- CDC radon and lung cancer overview — Centers for Disease Control and Prevention
- CDPHE radon program and Zone 1 data — Colorado Department of Public Health and Environment
- American Lung Association radon resources — American Lung Association
Front Range homeowners ready to check for radon in their home — or to mitigate after a high result — can contact our team for a referral to a NRPP-certified measurement professional and mitigation contractor.