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Radon Test Results Explained: What Your Number Means
You tested your home for radon and got a number. This guide explains what that number means using EPA and Iowa Health and Human Services guidance, and what to do next.
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The Short Version
- Below 2 pCi/L. Under EPA guidance, no action is needed. Radon can change over time, so retest about every two years and after major changes to the house.
- 2 to 4 pCi/L. The EPA says to consider fixing the home at this level.
- 4 pCi/L or higher. The EPA and the Iowa radon program recommend fixing the home.
- More than twice the action level on a first short-term test (above 8 pCi/L). The EPA guidance, as summarized by Iowa county health departments, is to take a second short-term test right away.
These are guidelines for deciding what to do next, not a measurement of anyone's health. The risk comes from breathing elevated levels over many years, and it rises with the level and the length of exposure.
Why Siouxland Results Above 4 Are Common
Every Iowa county is in the EPA's highest radon zone. The Iowa Department of Public Health reports an average indoor level of 8.5 pCi/L in Iowa, compared with 1.3 pCi/L for the United States. The Iowa Radon Survey found that 71.6 percent of the homes it measured were above the 4 pCi/L action level, and the American Lung Association's 2026 State of Lung Cancer report put the share of tested Iowa homes at or above the action level at about 58 percent.
The figures differ because they come from different sets of homes, but the message is the same. A high result is common in Iowa. It is a reason to act, not a reason to panic. Radon also varies from house to house, even on the same street, so a neighbor's result tells you little about yours. See radon in Sioux City and Iowa for the local background.
One Test Is a Snapshot
A short-term test measures for a few days and is the usual first step. A long-term test measures for more than 90 days and gives a better picture of your year-round average, which Iowa county health guidance recommends if you want to understand your typical level. Test the lowest lived-in level of the house and follow the kit's closed-house instructions. Our radon testing page walks through the steps.
If your result is close to 4, a second test or a long-term test is a sensible way to confirm it, since one short reading can land on either side of the line. If you are buying or selling, see testing for home sales.
If Your Number Calls for a Fix
A mitigation system typically has a suction point in the soil under the house, a vent pipe and a fan that runs continuously. In Iowa, professionals who install radon mitigation systems must hold a state credential, so ask to see it. After installation, retest to confirm the level dropped, and keep the paperwork together with your house records.
The radon mitigation page explains the job, and the cost factors guide explains what changes the scope of a job and how to compare proposals.
Iowa Rules Worth Knowing
- Selling a home. Under Iowa Code chapters 543B.9 and 543B.18, a seller must disclose any known radon test, with the date of the last report and the results, and the buyer acknowledges receiving the state radon fact sheet. No state rule requires testing or mitigation during a sale.
- New homes. Iowa House File 2297, signed May 19, 2026, directs the state building code commissioner to require a passive radon method from Appendix AF of the 2021 International Residential Code in new one- and two-family homes, applying to construction that starts after the requirement is adopted. The Iowa Health and Human Services radon page lists the requirement as beginning July 1, 2026, while the Department of Inspections, Appeals and Licensing has said it applies once the commissioner adopts it. Ask your builder or building office which applies to your project, and see new construction radon systems.
- Schools and child care. Iowa public schools must test for radon and mitigate when results are above 4 pCi/L, and licensed child care centers must test within a year of opening and mitigate above 4 pCi/L.
Free and Low-Cost Help
- Iowa Radon Hotline. The hotline at 1-800-383-5992, operated by the American Lung Association in Iowa with the state, can answer questions and point you to test kits and a list of credentialed professionals.
- Free test kits. The American Lung Association and Iowa Health and Human Services have offered free radon test kits while supplies last. Check lung.org/radon for current availability.
- County health departments. The Siouxland District Health Department has sold short-term kits to the public. Contact the department for current availability.
- January. Iowa observes Radon Action Month in January, when kits are most heavily promoted. A home can be tested at other times of year by following the kit's instructions.
Sources
Facts on this page come from the sources below. Check them for the latest numbers and rules.
Common Questions
What radon level is dangerous?
The EPA's action level is 4 pCi/L, and it recommends fixing a home at or above that level. The EPA also says to consider fixing between 2 and 4 pCi/L. The risk rises with the level and the length of exposure.
My test came back at 4.1. Do I need a system right away?
A result at or above 4 pCi/L is the level at which the EPA and the Iowa radon program recommend fixing the home. Because one short-term test is a snapshot, a second test is a reasonable way to confirm a result close to 4. A credentialed professional can advise on the next step.
How often should I retest?
Iowa health guidance recommends retesting about every two years, including homes that already have a mitigation system, and after major changes to the house.
Does an Iowa seller have to tell me about radon?
Under Iowa Code chapters 543B.9 and 543B.18, a seller must disclose any known radon test, including the date of the last report and the results. No state rule requires testing or mitigation during a sale.
Are new Iowa homes required to have radon systems?
Iowa House File 2297, signed May 19, 2026, directs the state building code commissioner to require a passive radon method in new one- and two-family homes, applying to construction that starts after the requirement is adopted. State agencies describe the start date differently, so ask your builder or building office.
Where can I get a free radon test kit in Iowa?
The American Lung Association and Iowa Health and Human Services have offered free kits while supplies last, and the Iowa Radon Hotline at 1-800-383-5992 can point you to kits. Check lung.org/radon for current availability.
Nearby Communities
We route requests from Sioux City and the surrounding area. Pick your town, or see the full service area list.
Know Your Radon Level, and Fix It If You Need To
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