How Long Does Radon Testing Take?
By Daniel SmokeDirector of Operations
Radon testing duration depends on the type of test. Short-term tests take two to seven days. Long-term tests run 90 days to one year. Each has appropriate use cases. Professional testing with proper protocols produces results that accurately represent your home's average radon level, the metric that determines actual health risk.
Short-Term Tests (2–7 Days)
Short-term radon tests use charcoal canisters, electret ion chambers, or continuous monitors deployed for a minimum of 48 hours up to seven days. They are the standard approach for real estate transactions because results can be returned within a week.
During a short-term test, the building must be in closed-house conditions, windows and exterior doors closed except for normal entry and exit. These conditions must hold for 12 hours before the test begins and throughout the test period. Short-term tests provide a snapshot of current conditions and can be elevated or depressed by temporary factors like weather or HVAC operation.
Long-Term Tests (90+ Days)
Long-term tests using alpha track detectors are left in place for 90 days to one year and measure radon exposure over time. Because radon levels fluctuate with weather, season, and building operation, long-term tests provide a more accurate picture of the average exposure that occupants actually experience. If your short-term test result is between 4 and 10 pCi/L, a follow-up long-term test before making a mitigation decision is often advisable. Long-term test results also serve well as the baseline for ongoing monitoring.
Continuous Electronic Monitors
Electronic radon monitors use ionization chambers or similar sensors to provide continuous readings, typically logged in hourly averages. These devices are often used by professionals for real estate testing. They provide time-stamped records that demonstrate closed-house conditions were maintained and can detect any test interference. They are also available for homeowners as ongoing monitoring tools. Professional-grade monitors provide data acceptable for regulatory purposes. Consumer devices vary significantly in accuracy.
Where Tests Should Be Placed
Radon testing should be conducted in the lowest livable level of the home, the lowest area used regularly, even occasionally, for living, sleeping, or recreation. For most homes, this is the ground floor or basement. Tests should not be placed in kitchens, bathrooms, laundry rooms, closets, or crawlspaces. Tests should be placed at least 20 inches above the floor and away from exterior walls and HVAC vents. In multi-zone homes, testing in multiple locations provides a more complete picture.
What Comes After Testing
After a short-term professional test, results are typically available within two to five business days after the test is retrieved and sent to the laboratory. The tester provides a written report with the measured radon level in pCi/L and a recommendation based on the EPA action level guidelines. If results are at or above 4 pCi/L, mitigation should be scheduled. If results are between 2 and 4 pCi/L, a follow-up long-term test or mitigation should be considered. Results below 2 pCi/L indicate low risk. Follow-up testing every two years is still recommended.
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