You sent out the test kit, waited a few days, and now you’re looking at a number like 3.8 pCi/L or 6.2 pCi/L trying to figure out what it means. Is it a problem? How big of a problem? And what are you supposed to do about it?
The answer comes down to where that number falls and what test conditions produced it.
What pCi/L Actually Measures
Radon is measured in picocuries per liter of air, abbreviated as pCi/L. This tells you the concentration of radon gas in your home’s indoor air. The higher the number, the more radon is present.
You don’t need to understand the physics behind picocuries to take action on your result. What matters is how your number compares to established thresholds. The U.S. Environmental Protection Agency recommends taking action when indoor radon reaches 4 pCi/L or above. The national average for indoor radon is about 1.3 pCi/L. Outdoor air typically measures around 0.4 pCi/L.
New Jersey’s geology puts many homes at higher baseline risk than the national average. The state’s Highlands and Piedmont regions contain bedrock with naturally elevated uranium content, which breaks down into radon and seeps upward into buildings. If you want to understand how radon forms and enters a home, that background helps explain why so many NJ properties test above average even without obvious entry points.
Reading the Number Ranges
Most radon test reports give you a single pCi/L value. Here is what each level means and what step to consider next.
| Result Range | Risk Level | Recommended Next Step |
|---|---|---|
| Below 2 pCi/L | Low | No action required. Retest every two years or after significant renovations. |
| 2 to 3.9 pCi/L | Moderate | Below the EPA action level, but worth confirming with a long-term test. Mitigation is worth discussing. |
| 4 to 7.9 pCi/L | Elevated | At or above the EPA action level. Radon mitigation is recommended. |
| 8 pCi/L and above | High | Mitigation should be a priority. These levels represent meaningfully greater long-term exposure. |
A properly installed sub-slab depressurization system reduces indoor radon by 80 to 99 percent in most NJ homes, regardless of the starting number. A high result is fixable.
Why Two Tests in the Same Home Can Show Different Numbers
Radon levels shift constantly. They respond to temperature, season, barometric pressure, and how the home is being used. A single short-term test gives you a useful snapshot, not a fixed reading for the property.
Short-term tests, which typically run 48 to 96 hours, are the most common format used during home purchases. They are fast enough to produce results before closing but are sensitive to conditions during the testing window. Long-term tests, which run 90 days to a year, reflect the actual average annual radon exposure in the home and are generally more reliable for ongoing monitoring.
Variables that affect the number you see:
- Test placement: radon concentrations peak at the lowest livable level of the home, typically the basement or first floor
- Season: levels tend to rise in winter when homes are sealed and the pressure differential between soil and interior air increases
- Foundation type: basements, crawl spaces, and slab-on-grade homes each interact with ground-level radon differently
- Local geology: homes in NJ’s Highlands and Piedmont regions tend to produce higher readings due to uranium-bearing bedrock
- Ventilation: open windows or fans during the testing window can artificially lower a short-term result
If your short-term result came in between 2 and 4 pCi/L, a follow-up long-term test can help confirm whether you’re consistently near the threshold. If the result was well above 4, the confirmation step is generally not necessary before moving forward with mitigation.
What Makes a Radon Test Result Valid
A test is only as reliable as the conditions it was conducted in. Homeowners sometimes receive results that are misleadingly low because testing protocols weren’t followed correctly, particularly during real estate transactions where the home may have been aired out or vacant before the kit was placed.
For a short-term test to be considered valid:
- The device should be placed in the lowest livable area of the home, not a storage room or unfinished space
- Doors and windows should remain closed for at least 12 hours before the test begins and throughout the testing period
- The device should not sit near drafts, air vents, exterior walls, or direct sunlight
- It should be positioned at breathing level, between 20 inches and 6 feet off the floor
- The kit should be mailed back or picked up within the window specified by the manufacturer
If the conditions during your test don’t match these guidelines, the result may not accurately reflect what a normally occupied home would show. This matters most when your number sits close to the 4 pCi/L threshold in either direction.
Acting on a Result Above 4 pCi/L
A result above the EPA action level does not mean your home is unsafe to live in. It means radon has been accumulating at a level worth addressing, and that a mitigation system will significantly reduce your family’s long-term exposure.
The standard approach in New Jersey is sub-slab depressurization. A contractor installs a pipe through the foundation and attaches a fan that draws radon-laden air from beneath the slab before it enters the living space. The system operates continuously, runs quietly, and requires minimal ongoing maintenance.
If your home uses a private well, it is also worth checking for radon in your water supply. Groundwater in high-radon geology can carry dissolved radon that gets released into the air during showering, dishwashing, or any other water use. Soil radon and water radon require separate tests and separate treatment systems.
For a full breakdown of what to do after a high result, including how to navigate the process during a home purchase, see what to do after a failed NJ radon test.
How Jersey Radon Helps After a Result Comes Back
Whether your result is just above 4 pCi/L or significantly higher, the path forward is the same: a licensed NJ mitigation contractor assesses the home, recommends the right system, and installs it. Jersey Radon handles all of this for homeowners throughout New Jersey, with free estimates and no pressure to commit before you’re ready.
Homeowners typically contact us after:
- Receiving an elevated result during a home purchase inspection
- Getting a long-term test back on a home they have lived in for years
- Retesting after finishing a basement and wanting to confirm levels before using the space regularly
- Being told radon was found during an inspection but not receiving clear guidance on next steps
- Wanting a second opinion after a contractor’s quote didn’t include a clear explanation of the approach
If your radon test came back above 4 pCi/L and you want to understand what mitigation involves, schedule a free estimate with Jersey Radon. We serve all of New Jersey and can typically get a system installed shortly after the initial site visit.
