How Often Should You Test Your Home for Radon? A Complete Guide

The Short Answer: Test Every Two Years

The EPA and most state health departments recommend testing your home for radon at least every two years. If you've never tested, do it now — regardless of when you moved in.

Radon levels aren't static. They shift with changes to your home's foundation, soil conditions, seasonal pressure differences, and indoor ventilation patterns. A test from five years ago tells you almost nothing about what's happening today.

A certified inspector placing both a continuous monitor and a passive test canister during a baseline inspection.

When You Should Test More Frequently

Every two years is the minimum. These situations call for immediate or more frequent testing:

Test now (don't wait) if:

• You've never tested your current home
• You're buying or selling a home
• You've finished a basement or added livable space below grade
• You've had major HVAC work, sealed crawl spaces, or foundation repairs
• Your last test was more than two years ago

Test annually if:

• Your previous test came back between 2–4 pCi/L (the "watch zone")
• You live in a radon zone 1 area (highest potential — check the EPA map)
• Your home has a crawl space that wasn't previously sealed

After mitigation: Retest 30–90 days after any mitigation system is installed, then annually for the first two years, then every two years if levels remain below 2 pCi/L.

Short-Term vs. Long-Term Testing

There are two main test types, and both have a place depending on your situation.

Short-term tests (2–90 days): Usually charcoal canisters or electronic monitors. Fast results, lower cost, ideal for real estate transactions. Less accurate because they capture a snapshot rather than a seasonal average.

Long-term tests (90 days to 1 year): Alpha track detectors are the most common. These give you an annual average, which is what EPA guidelines are actually based on. More accurate, but slower.

For initial baseline testing, a long-term test gives you the most actionable data. For confirming a high short-term result or verifying a mitigation system, a short-term test is fine.

Long-term alpha track detectors and continuous monitors both have a role depending on what you're trying to learn.

Where to Test in Your Home

Test on the lowest livable level — the floor where you spend the most time. For most homes, that's the first floor. If you use the basement regularly (as a bedroom, office, or workout space), test there.

Don't test in:

• Kitchens or bathrooms (humidity and ventilation skew results)
• Crawl spaces (not a livable area)
• Garages

If you have a two-story house with a basement you use occasionally, it's worth testing both the basement and first floor separately.

DIY vs. Professional Testing

DIY kits work fine for routine testing. Send-in kits from the NRPP-approved labs run $15–$30 and give lab-certified results. The key is following closed-house conditions during testing (windows and exterior doors closed except for normal entry/exit for 12–24 hours before and during the test).

Professional testing makes sense for:

• Real estate transactions (certified third-party results carry more weight)
• Initial baseline if you have complex foundation types
• Post-mitigation verification

Many certified radon testing professionals are also licensed for other home inspection services. In areas with active water quality concerns, some inspectors hold both radon and backflow testing certifications.

Proactive testing — before problems appear — is the only reliable way to know your home's radon status.

Setting Up a Testing Schedule

Here's a simple schedule that works for most homeowners:

Situation	When to Test
First time testing	Right now
After mitigation	30–90 days post-install, then annually
Previous result 2–4 pCi/L	Every year
Previous result below 2 pCi/L	Every 2 years
Major renovation or foundation work	Immediately after
Buying a home	Before closing

The Bottom Line

Radon testing is cheap (under $30 for a kit), fast (48 hours for a short-term test), and the only way to know what you're actually breathing. The two-year cycle is a minimum baseline. If anything in your home changes — renovations, new family members sleeping in the basement, a move — test again.

The risk is invisible. The test isn't.