What Your Radon Test Results Mean

A radon test comes back with one number and not much explanation, and people understandably wonder whether it is fine or a problem. Since Kansas City sits in the EPA's highest radon zone, we get asked this a lot. Here is how to read the result and what to do about it.

What pCi/L means

Radon is measured in picocuries per liter of air, written pCi/L. It is simply a measure of how much radioactive radon gas is in the air of the space you tested. A higher number means more radon in the air you and your family breathe. There is no completely risk-free level, but the number tells you how much action makes sense.

The 4.0 action level

The EPA recommends fixing a home when a test comes back at 4.0 pCi/L or higher. If your result is below 4.0 but still above 2.0, the EPA suggests you consider fixing it, since risk exists at lower levels too. Below 2.0 is generally seen as low. Homes in the Kansas City area test above 4.0 often enough that we would never treat a high result as unusual.

Why one reading is not the whole story

Radon moves around. It changes with the weather, the season, how tightly the house is closed up, and whether the furnace is running. A short-term test over a few days gives a useful snapshot, and a long-term test or continuous monitor shows the average over time. If a first result is at or just over 4.0, a second test is a smart follow-up before you decide anything. We compare the two approaches in our post on radon testing vs continuous monitoring.

What to do with a high result

A confirmed result of 4.0 or higher means it is time to look at mitigation. A licensed pro can install a sub-slab depressurization system that pulls the gas from under the foundation and vents it above the roofline. See our radon mitigation system installation page for how that works, and our radon testing page if you still need a test.

Frequently asked questions