How To Read A Radon Test Result In A Bismarck-Mandan Home
A radon test report shows one figure, measured in picocuries per liter (pCi/L), plus the device type, test dates, and placement. For homeowners in Bismarck, Mandan, Lincoln, and the wider Burleigh and Morton County area, where both counties sit in EPA Zone 1, that figure is compared with the EPA’s action level of 4 pCi/L. The sections below explain what each range means, when a second test makes sense, and how to confirm a fix worked. For how a test is set up and run, see the radon testing guide.
What Different Radon Levels Mean
Results sit on a continuous scale rather than a pass-or-fail line, and EPA guidance breaks it into practical ranges:
- Below 2 pCi/L: Generally no action is needed. The EPA cites roughly 0.4 pCi/L as a typical outdoor level and about 1.3 pCi/L as an average indoor level nationwide.
- 2 to 3.9 pCi/L: The EPA suggests considering a fix, since levels under the action level still carry some risk.
- 4 to 7.9 pCi/L: At or above the action level. Follow-up testing and mitigation planning are the standard next steps.
- 8 pCi/L and above: Well over the action level. A prompt second test and a look at mitigation options are the usual response.
Some lab reports use becquerels per cubic meter (Bq/m³). A result of 4 pCi/L equals about 148 Bq/m³, so the same thresholds apply.
Why Two Bismarck-Area Homes Can Test Differently
A result describes one house, in one spot, during one test period. Soil under the foundation, cracks and sump pits, construction details, and heating-season air movement all shape the number. Much of the Bismarck-Mandan area sits on glacial till and clay-rich soils, and tight soils change how soil gas travels beneath a slab, which is why a neighbor’s result is not a substitute for testing your own property. Placement matters too, so the lowest livable level is the standard reference point.
Short-Term And Long-Term Results Can Differ
A short-term test, typically 2 to 90 days and most often 2 to 7 in a home sale, is a snapshot. Radon moves with weather and how tightly a house is closed up, so a short-term number can land above or below a home’s year-round average. A long-term test of more than 90 days smooths those swings out, which makes it a steadier basis for a decision when a short-term result lands near 4 pCi/L. When two tests are run, the usual practice is to compare their average with the action level.
Follow-Up Testing After A High Result
EPA guidance for a first result at or above 4 pCi/L is to run a second test. If the first number is roughly twice the action level or more, a second short-term test right away is the usual route. Keep conditions consistent: closed-house protocol, the same lowest livable level, and a device left undisturbed. If the average is 4 pCi/L or higher, the next step is mitigation. The system installation page explains how an active system is planned, and sub-slab depressurization covers the method most Bismarck-area basements use.
Test Results During A Home Sale
A result at or above 4 pCi/L during an inspection period usually leads to a conversation about installing a system or adjusting terms, with the closing date compressing everything. Ask for the full report: device type, placement, start and end times, and notes about disturbed conditions. See the real estate radon testing page for timing, and note that buyers of newer homes should still test even when radon-resistant features were built in.
Confirming That A Fix Worked
After installation, a new test confirms the number dropped below 4 pCi/L. The EPA also advises retesting every two years and after a remodel, foundation repair, or ventilation change. Many active systems include a simple pressure indicator on the pipe, so a quick look now and then shows whether the fan is still moving air.
Next Steps
Keep the full report, follow-up results, and post-mitigation test together for a later sale or provider conversation. When you are ready to move from a confirmed result to a quote, the mitigation cost guide explains what affects pricing, and the same approach applies in Mandan and across Burleigh County. Mitigation work described on this site is performed by licensed, insured local professionals.
Radon Test Result Questions
- What is a high radon level in Bismarck?
- The EPA recommends fixing a home at 4 pCi/L or above. Burleigh and Morton Counties are both in EPA Zone 1, but the only way to know a specific home's level is to test it.
- Is 3 pCi/L a bad radon result?
- It is under the action level, but the EPA suggests considering a fix between 2 and 4 pCi/L. A follow-up test, especially a long-term one, can help you decide.
- Should I retest if my first result was high?
- Yes. A first result at or above 4 pCi/L is normally followed by a second test, since one short-term test is only a snapshot.
- Can radon levels change from season to season?
- Yes. Weather, air pressure, and how tightly a home is sealed all affect readings, and North Dakota homes are closed up tightest during the heating season.
- How do I know a radon system is working?
- Test again after installation to confirm the result is under 4 pCi/L, then retest every couple of years and after major remodels.