Testing your home for radon once is not enough. Unlike checking for carbon monoxide detectors or smoke alarms, radon testing needs to happen periodically because levels can change over time. Understanding when and how often to test ensures your family stays protected.
This guide explains the EPA's testing recommendations, when special circumstances call for immediate retesting, and how to create a testing schedule that keeps your home safe year after year.
Quick Reference: When to Test
- Every 2-5 years: Standard retesting for all homes
- After renovations: Any work affecting foundation, basement, or HVAC
- Every 2 years: If you have a mitigation system
- When buying/selling: Always test during real estate transactions
1. EPA Testing Guidelines
The Environmental Protection Agency (EPA) provides clear guidance on radon testing frequency. Their recommendations are based on decades of research into how radon levels behave in homes over time.
EPA Testing Recommendations
- 1Test all homes: Every home should be tested regardless of age, construction type, or geographic location
- 2Retest every 2-5 years: Even if previous results were low, conditions can change
- 3Test after changes: Retest after renovations, HVAC modifications, or changes to home ventilation
- 4Test the lowest level: Test the lowest regularly occupied level of your home
The EPA emphasizes that there is no known safe level of radon exposure. While 4 pCi/L is the action level, they also recommend considering mitigation for levels between 2-4 pCi/L. Regular testing helps you track any changes and respond appropriately.
2. Your First Radon Test
If you have never tested your home, now is the time. Do not wait for a specific season or event. The health risks of prolonged radon exposure far outweigh any benefit of waiting for ideal testing conditions.
Test These Homes Immediately
- • Homes that have never been tested
- • Homes where you do not know the testing history
- • Homes in EPA Zone 1 or Zone 2 areas
- • Homes with basements or crawl spaces
- • Homes where you are considering having children
Your first test establishes a baseline. This baseline tells you whether immediate action is needed and gives you a reference point for future tests. Even if results are low, you will want to verify that levels remain stable over time.
First Test Options
Professional Testing
Best option for accurate results. Continuous radon monitors provide hourly readings and tamper detection. Recommended for establishing your baseline.
Cost: $125-$300
DIY Test Kit
Acceptable for initial screening. Purchase from hardware stores or online. Follow instructions carefully for accurate results.
Cost: $15-$50
3. Regular Retesting Schedule
Once you have your baseline, establish a regular retesting schedule. How often you test depends on your initial results and whether you have a mitigation system.
Low Results (Below 2 pCi/L)
Retest every 5 years, or sooner if you make changes to your home. Continue monitoring to ensure levels remain stable.
Moderate Results (2-4 pCi/L)
Retest every 2-3 years. Consider a long-term test to get a more accurate annual average. Mitigation may be worth considering.
High Results (4+ pCi/L)
Do not delay. Confirm with a second test and install mitigation. After mitigation, test every 2 years to verify system effectiveness.
Many homeowners find it helpful to schedule radon testing at the same time each year, just like HVAC maintenance or annual home inspections. This creates a routine that ensures testing does not get forgotten.
4. Testing After Home Changes
Certain home modifications can significantly affect radon levels. Some changes create new entry points for radon, while others alter air pressure dynamics that influence how much radon enters your living space.
Always Retest After:
Foundation Work
- • Foundation repairs
- • Basement waterproofing
- • Sump pump installation
- • Floor drain modifications
- • Crawl space encapsulation
HVAC Changes
- • New heating or cooling system
- • Ductwork modifications
- • Adding exhaust fans
- • Whole-house ventilation systems
- • Air sealing projects
Major Renovations
- • Basement finishing
- • Room additions
- • Converting garage to living space
- • Major remodeling projects
Energy Efficiency Upgrades
- • New windows and doors
- • Insulation upgrades
- • Air sealing
- • Weatherization
Wait 30-60 days after completing renovations before testing. This allows the home to stabilize and provides results that reflect ongoing conditions rather than temporary construction effects.
5. Testing with Mitigation Systems
If you have a radon mitigation system, regular testing is even more important. While these systems are highly reliable, fans can fail, and conditions can change. Testing confirms your system continues to protect your family.
Mitigation System Testing Schedule
- 24-48 hours after installation: Post-mitigation test to verify system effectiveness
- Every 2 years: Routine verification that the system maintains low levels
- After fan replacement: Confirm the new fan provides adequate suction
- If manometer shows issues: Test immediately if the gauge indicates loss of suction
Between formal tests, check your manometer monthly. The liquid levels should be uneven, indicating the fan is creating suction. If levels appear equal, or if you notice unusual sounds from the fan, schedule testing right away.
6. Seasonal Considerations
Radon levels in your home can vary by season. Understanding these patterns helps you interpret test results and decide when to test for the most useful information.
❄️ Winter Testing
November through March typically shows highest levels.
- • Windows and doors closed
- • Heating creates stack effect
- • Negative pressure draws in soil gases
- • Frozen ground concentrates radon
Recommended for most testing
☀️ Summer Testing
May through September typically shows lower levels.
- • Open windows increase ventilation
- • Air conditioning can vary effects
- • More natural air exchange
- • Soil radon more dispersed
Still valuable, but may underestimate peak levels
While winter testing typically captures higher levels, do not delay testing just to wait for cold weather. If you have never tested, test now. You can always retest in winter for comparison. The goal is to know your home's radon situation and take action if needed.
For the most complete picture, consider a long-term test (90+ days) that spans multiple seasons. This provides an annual average that accounts for seasonal variations.
7. Special Circumstances
Certain life situations may warrant more frequent testing or immediate retesting, even if you are within your normal testing cycle.
Pregnancy or New Baby
Children are more vulnerable to radon exposure. If you are expecting or have recently had a baby, test to ensure your home is safe for your growing family.
Moving to a Different Level
If you start spending more time on a lower level (such as finishing a basement bedroom), test that level. Radon concentrations are typically highest closest to the ground.
Nearby Construction or Excavation
Major construction activity nearby, especially excavation, can temporarily affect soil gas movement. Consider retesting if significant earth-moving occurs on adjacent properties.
Earthquake or Ground Settling
Seismic activity or noticeable foundation settling can create new pathways for radon entry. Retest if you notice new cracks or changes in your foundation.
8. Short-Term vs Long-Term Tests
Radon tests come in two main types, each with different purposes. Understanding when to use each type helps you get the most useful information.
Short-Term Tests
Duration: 2-7 days (48 hours minimum)
Best For:
- • Real estate transactions
- • Quick screening
- • Post-mitigation verification
- • Confirming high results
Considerations:
- • Results can vary with weather
- • May not capture seasonal variation
- • Good for immediate decisions
Long-Term Tests
Duration: 90 days to 1 year
Best For:
- • Annual average measurement
- • Comprehensive risk assessment
- • Homes with borderline results
- • Understanding seasonal patterns
Considerations:
- • More accurate overall picture
- • Takes longer to get results
- • Best for long-term planning
Many professionals recommend starting with a short-term test. If results are clearly elevated (above 4 pCi/L), take action. If results are moderate (2-4 pCi/L), a long-term test can help determine whether mitigation is worthwhile.
