Safety

How Often Should You Test for Radon?

The EPA recommends radon testing every 2 years. Radon is the second leading cause of lung cancer in the US — and most homes have never been tested.

Test every 2 years (EPA)

Quick Facts

Recommended Interval

Test every 2 years (EPA)

Typical Cost

$15–$35 (DIY kit) / $100–$200 (professional)

Source

EPA

Overview

Radon is a naturally occurring radioactive gas produced by the breakdown of uranium in soil and rock. It is odorless, colorless, and the second leading cause of lung cancer in the United States — responsible for approximately 21,000 lung cancer deaths per year according to the EPA. Radon enters homes through foundation cracks, sump pits, and other openings. The EPA recommends testing every 2 years and after any major renovations that disturb the foundation or change air pathways. Short-term test kits (48 hours to 90 days) are available at hardware stores for $15–$35 and provide actionable results.

Signs You Are Overdue

No recent test (or never tested) — this is the primary indicator that action is needed
Previous test was over 2 years ago
Major renovations completed since last test — crawlspace work, basement finishing, foundation repairs
Home has a basement or is in a historically high-radon geographic area (Midwest, Mountain West)
Previous test showed levels between 2–4 pCi/L — retest to confirm

How to Stay on Schedule

Test in the lowest livable area of the home — basement if finished, first floor if not
Keep windows and doors closed during the test period for accurate short-term results
Test again after any mitigation system is installed to confirm it is working
Test seasonally if previous results were near the 4 pCi/L action level — levels vary
Check radon levels again when buying or selling a home

What Affects Replacement Cost

DIY short-term test vs. professional long-term test vs. continuous electronic monitor
Radon mitigation system if levels exceed 4 pCi/L action level — $800–$2,500 installed
Geographic location — high-radon areas (Midwest, Montana, Idaho) have higher average levels

Why the Schedule Matters

Test for radon every 2 years per EPA guidelines, after any renovation work that affects the foundation, and when moving into any home that has not been recently tested. The EPA action level is 4 pCi/L — at this level, mitigation is strongly recommended. Levels between 2–4 pCi/L should be monitored and mitigation considered. Radon mitigation systems (sub-slab depressurization) are highly effective, reducing levels by 50–99%.

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Pro Tip

Radon levels vary significantly by season — they are typically highest in winter when homes are sealed and lowest in summer. For the most accurate long-term assessment, an electronic continuous radon monitor ($100–$200) is more reliable than a single short-term test. If you get a high short-term result, confirm with a 90-day long-term test before investing in mitigation.

Frequently Asked Questions

What radon level is dangerous?+

The EPA recommends action when radon levels reach 4 pCi/L (picocuries per liter). Levels between 2–4 pCi/L are in a gray zone where mitigation should be considered. There is no "safe" level of radon, but the risk below 2 pCi/L is considered low. The US average indoor radon level is 1.3 pCi/L.

How much does radon mitigation cost?+

Radon mitigation (typically sub-slab depressurization — installing a vent pipe and fan system) costs $800–$2,500 installed and reduces indoor radon levels by 50–99%. The system requires a small fan that uses about $30–$60/year in electricity. Follow-up testing after installation confirms effectiveness.