How Often Should You Test for Radon in Indiana?

March 2, 2026

Testing for radon is not a one-time event. Radon levels change over time — with the seasons, as homes settle and develop new foundation cracks, after renovations, and after changes in ventilation. Indiana homeowners should have a testing schedule, not just a test.

The Initial Test: If You’ve Never Tested

If you have never tested your Indiana home for radon, test now. This applies regardless of:

• Home age — New homes can have elevated radon. Old homes can have low radon. Age is not predictive.
• County — Even Zone 2 counties have homes testing above 4 pCi/L. The zone is a county average, not a guarantee for your specific property.
• Basement presence — Slab-on-grade and crawl space homes can also have elevated radon, though basement homes are at highest risk.

How to test: Use either a short-term test (48–96 hours, closed-house conditions) or a long-term test (90+ days). Short-term tests give fast results; long-term tests are more accurate because they average out daily and seasonal fluctuations.

For a home sale or negotiation, use a certified Indiana radon tester — their results carry more weight than a DIY kit. For routine homeowner purposes, a quality short-term kit from a hardware store ($15–$30) gives a reasonable result.

If Your Initial Test is Below 2 pCi/L

At or below 2 pCi/L, the EPA considers the risk low. No mitigation is required. However:

• Retest every 5 years. Foundation conditions change, and a result from 10 years ago may no longer reflect current levels.
• Consider retesting if you make changes that affect ventilation or foundation integrity (see below).

If Your Initial Test is 2–4 pCi/L

The EPA recommends considering mitigation in this range, especially for:

• Long-term residents (more total exposure time)
• Smokers or former smokers (radon and tobacco are synergistic)
• Homes where children spend significant time in lower levels

Retest with a long-term test (90+ days) to get an accurate average before deciding. A single short-term test in the 2–4 range warrants a confirming test before committing to mitigation.

If Your Initial Test is At or Above 4 pCi/L

Mitigation is strongly recommended by the EPA. At 4 pCi/L, the EPA estimates a non-smoker’s lifetime risk of radon-induced lung cancer at roughly 7 in 1,000. For smokers, approximately 29 in 1,000.

Confirm before acting: A second short-term test (or one long-term test) confirms the result. Then contact a licensed Indiana radon mitigator.

Do not wait years. Elevated radon is a present risk, not a future one. Every year in a high-radon home adds to cumulative exposure.

Post-Mitigation Testing Schedule

After a mitigation system is installed:

Immediate post-mitigation test (24–48 hours): Required. This confirms the system achieved adequate reduction. Your contractor should perform this or arrange it. The target is generally below 2 pCi/L — the average U.S. indoor level.

Annual test for the first two years: Some AARST-certified mitigators recommend testing at 12 and 24 months after installation to establish a baseline and confirm the system is stable before moving to a 2-year schedule.

Every two years thereafter: The EPA and AARST both recommend biennial testing for mitigated homes. The radon mitigation industry standard in Indiana follows this schedule.

Life Events That Should Trigger a New Test

Even if you tested recently, retest after any of these:

Renovation or foundation work. Drilling through a slab for plumbing, adding a basement finishing project, underpinning, or installing a sump pump can disrupt existing sub-slab pressure dynamics and create new radon entry points.

Moving into a home you didn’t build. A radon test report from a prior owner or real estate transaction may be years old. Test within 90 days of occupancy.

System or HVAC changes. Adding a whole-home ventilation system, ERV, or HRV changes how air moves through your home. An ERV that over-pressurizes the home could actually interfere with sub-slab depressurization systems. Retest after major HVAC changes.

Fan failure and replacement. After replacing a failed mitigation fan, a post-replacement test confirms the new fan restored adequate suction.

Buying a home with an existing mitigation system. The prior system may have been sized for different conditions, or the fan may be aging. Test with the system running. If results are above 4 pCi/L despite an active system, a mitigator may need to diagnose and adjust it.

Indiana’s Testing Season

Indiana’s climate matters for testing strategy:

• Winter (December–February): Highest radon readings. Homes are sealed, temperature differential is greatest, stack effect is strongest. This gives the most conservative (worst-case) result.
• Spring/Fall: Moderate readings. Good for routine retesting.
• Summer: Lowest readings in most homes. Open windows and reduced stack effect lower measured levels. A summer test may underestimate your true annual average.

Recommendation for first-time testers: Test in fall through early spring if possible. If you’re buying a home with a 48-hour inspection window in summer, a marginal result (2–4 pCi/L) warrants a follow-up long-term test.

Keeping Records

Keep documentation of every radon test:

• Date of test and test method (short-term vs. long-term)
• Lab result in pCi/L
• Whether windows were closed during testing
• Current mitigation system status (if installed)

This history is valuable when you sell the home, file an insurance claim, or need to assess whether your mitigation system is degrading over time.

Find a licensed Indiana radon tester to conduct a certified measurement — browse by county on this site.