Understanding Your Radon Test Results

What the Numbers on Your Radon Report Actually Mean

You've tested your home for radon, and now you're staring at a number. Maybe it's 2.8. Maybe it's 6.1. Perhaps the report says 0.9 pCi/L and you're not sure whether to be relieved or skeptical. Before you do anything else — call a contractor, dismiss the result, or retest — it helps to understand what that number actually represents and where it sits on the risk scale the EPA uses.

Radon levels are measured in picocuries per liter of air, abbreviated as pCi/L. A picocurie is a unit of radioactivity — specifically, the amount of a radioactive substance that undergoes 2.22 nuclear disintegrations per minute. For radon in a home, this translates practically to: the higher the pCi/L reading, the more radon gas is present in your living space, and the more consistently you and your family are inhaling it over time.

The national average indoor radon level in the United States is approximately 1.3 pCi/L, and the average outdoor air level is about 0.4 pCi/L. Those two numbers give you a baseline. A home at 1.3 pCi/L is about average. A home at 4.0 pCi/L has roughly three times the average indoor concentration. A home at 8.0 pCi/L has about six times the average. These aren't dramatic differences in absolute terms — radon is always present to some degree — but when you're breathing that air for years, the cumulative exposure to radiation matters for long-term lung health.

The EPA Action Level — 4.0 pCi/L

The U.S. Environmental Protection Agency has established 4.0 pCi/L as the residential action level for radon. This is the concentration at which the EPA recommends taking steps to reduce radon in your home. If your test result comes back at or above 4.0 pCi/L, the guidance is clear: mitigate. This recommendation is based on decades of research linking long-term radon exposure to elevated lung cancer risk — radon is, in fact, the leading cause of lung cancer among non-smokers in the United States.

The EPA also draws a line between 2.0 and 3.9 pCi/L, which it calls a range where mitigation is "worth considering." This grey zone matters most if you spend significant time on the lower levels of your home — a finished basement, a ground-floor bedroom — or if children live in the home, since younger lungs face proportionally greater cumulative risk from continuous low-level exposure.

Below 2.0 pCi/L, the EPA considers the risk low. A result in this range is genuinely good news, not just reassurance. No action is needed, and there's no current guidance to retest unless conditions in your home change significantly — major renovations, a new HVAC system, or a change in how you use lower levels.

What to Do at Each Level

Below 2.0 pCi/L — You're in the low-risk range

A result below 2.0 pCi/L means radon concentrations in your home are consistent with what the EPA considers acceptable. No mitigation is needed. You can file the certified report with your home records — it's useful documentation if you sell the home — and plan to retest in five to seven years, or sooner if you make significant changes to the structure.

2.0–3.9 pCi/L — Consider your circumstances

Results in this band warrant a thoughtful conversation rather than immediate action. How much time do you spend in the lowest level of your home? Are there young children or family members with elevated lung cancer risk? Are you planning to sell soon? If the answer to any of these is "yes," a consultation with a certified radon remediation contractor makes sense. Mitigation in this range is often straightforward and relatively affordable.

4.0 pCi/L and above — Act

This is the EPA's threshold for action, and the recommendation is unambiguous: pursue mitigation. That doesn't mean panic — elevated radon is a fixable problem, not a permanent one. Radon remediation systems are effective, professionally installed in most cases in a single day, and bring elevated levels down reliably, often to below 2.0 pCi/L. The sooner you address it, the less cumulative exposure your family faces.

Short-Term vs. Long-Term Tests

Most residential radon tests are short-term tests, conducted over 48 to 96 hours using a passive charcoal canister. These are the standard for real estate transactions and first-time testing because they're fast and give a defensible snapshot. However, radon levels can vary with seasons, weather changes, and how tightly your home is sealed, which means a single short-term test captures conditions at one specific point in time.

Long-term tests — typically electret ion chamber or alpha track detectors left in place for 90 days to a year — give a time-averaged result that accounts for seasonal variation. If your short-term test comes back in the 3.0–5.0 pCi/L range and you want more certainty before committing to mitigation, a follow-up long-term test can clarify the picture. That said, if your short-term result is significantly above 4.0 pCi/L, most certified professionals recommend acting on it rather than waiting for a long-term confirmation.

Why the Test Method Matters

The reliability of a radon test result depends heavily on how the test was conducted. Certified testing professionals use calibrated equipment, place detectors in the correct location (lowest livable level of the home), follow closed-house conditions, and ensure the test period meets EPA protocols. These conditions aren't arbitrary — they're designed to produce a result you can actually trust and use to make decisions.

A professionally conducted test also gives you a certified written report, which carries more weight than a do-it-yourself mail-in kit for real estate disclosures, permit applications, and post-mitigation verification. When in doubt about your result, retesting with a certified professional is the most straightforward way to get clarity.

Your Next Steps

Now that you understand what your radon test result means, the path forward depends on where you landed:

• Under 2.0 pCi/L: File the report, schedule a retest in five to seven years.
• 2.0–3.9 pCi/L: Consider your household circumstances and consult a certified contractor.
• 4.0 pCi/L and above: Move forward with radon remediation.

If you're in Kannapolis, Concord, or Landis and need a certified initial test — or a post-mitigation verification test — Wightman Inspection Group uses professionally calibrated equipment and provides a written report that tells you exactly where you stand.