By Gregory Anzano, DGM Inspection | NJ Licensed Home Inspector #24GI00201100
If you are buying or selling a home anywhere in Middlesex County, radon is one of those topics that comes up in almost every transaction, and for good reason. New Jersey sits on some of the most radon prone geology in the country, and homes from Edison to East Brunswick to Old Bridge regularly test above the federal action level. The good news is that radon is easy to measure and very fixable. The key is understanding what radon testing in NJ actually involves and what your results mean when the report comes back.
After years of inspecting homes across Central Jersey, I have seen radon results that surprised buyers in every direction. Brand new construction in Monroe Township testing high. A 1920s colonial in Highland Park testing low. The only way to know is to test, and this guide walks you through why our state tests the way it does, how the numbers work, and what to do next.
What Is Radon and Why Should NJ Homeowners Care?
Radon is a naturally occurring radioactive gas that forms when uranium in soil and rock breaks down. You cannot see it, smell it, or taste it. It seeps up from the ground and enters homes through cracks in foundations, sump pits, crawl spaces, gaps around pipes, and even well water. Once inside, it can build up to unhealthy concentrations, especially in basements and lower living levels.
The health stakes are real. Radon is the leading cause of lung cancer among people who have never smoked, and the second leading cause of lung cancer overall according to the EPA. Because there are no immediate symptoms, the only way to know your exposure is a proper radon test.
Why Do So Many New Jersey Homes Test High for Radon?
New Jersey has a geology problem, at least where radon is concerned. A band of uranium rich bedrock known as the Reading Prong runs through the northwestern part of the state, and glacial deposits spread radon producing material across a much wider area over time. That is why counties like Hunterdon, Warren, Sussex, and Morris are famous for high radon readings, and why elevated results show up throughout Central Jersey too.
The New Jersey Department of Environmental Protection maps every municipality into one of three radon potential tiers based on actual test results:
- Tier 1, High Potential: At least 25 percent of tested homes at or above 4 pCi/L
- Tier 2, Moderate Potential: Between 5 and 24 percent of tested homes at or above 4 pCi/L
- Tier 3, Low Potential: Fewer than 5 percent of tested homes at or above 4 pCi/L
Here is the part many homeowners in Piscataway, Woodbridge, and Sayreville miss: the tier map describes probability, not your house. The NJDEP is clear that radon levels can vary widely even within a single tier, because soil composition changes from lot to lot. I have tested two homes on the same street in South Brunswick where one came back under 1 pCi/L and the neighbor needed mitigation. Regardless of tier, the NJDEP recommends every home in the state be tested.
| Inspector’s Note: Do not skip radon testing because your town is listed as moderate or low potential. Tier maps predict neighborhoods, not individual houses. Your foundation, soil, and construction details decide your actual number |
What Do Radon Test Numbers Actually Mean?
Radon is measured in picocuries per liter of air, written as pCi/L. When your radon testing results come back, here is how to read them:
| Radon Level (pCi/L) | What It Means | Recommended Action |
| Below 2.0 | Low. Comparable to typical outdoor background levels in many areas. | No action needed. Retest every 2 to 5 years or after major renovations. |
| 2.0 to 3.9 | Elevated but below the federal action level. The EPA suggests considering a fix in this range. | Consider mitigation, especially if you spend a lot of time in the basement. Retest periodically. |
| 4.0 and above | At or above the EPA and NJDEP action level. | Mitigation is recommended. In a real estate deal, this number typically triggers negotiation. |
| 10.0 and above | Significantly elevated. Not rare in parts of New Jersey. | Mitigate promptly and retest to confirm the system brought levels down. |
The number 4.0 pCi/L is the one to remember. Both the EPA and the NJDEP recommend fixing your home at or above that level. It is not a cliff where 3.9 is safe and 4.1 is dangerous. There is no known fully safe level of radon, which is why the EPA also suggests considering mitigation between 2 and 4 pCi/L. The action level is simply the point where the health benefit of fixing the problem clearly justifies the cost.
Schedule Radon Testing with Your Home InspectionDGM Inspection provides professional radon testing across Middlesex County and Central Jersey, as a standalone service or bundled with your full home inspection. One visit, clear results, and a straight answer about what your numbers mean. Visit dgminspection.com to book your radon test today. |
How Professional Radon Testing in NJ Works
New Jersey takes radon seriously enough that radon measurement businesses must be certified through the NJDEP. That certification matters because a radon test is only as good as the protocol behind it. Here is what a professional short term test looks like during a typical Central Jersey home purchase:
- Placement: A continuous radon monitor or approved test device is placed in the lowest livable level of the home, usually the basement, away from drafts, windows, and exterior walls.
- Closed house conditions: Windows and doors stay closed except for normal entry and exit for at least 12 hours before the test and for the full test period. This keeps the reading honest.
- Duration: The device measures for a minimum of 48 hours. Continuous monitors log hourly readings, which also helps flag any tampering or unusual conditions.
- Results: You receive a report with the average radon concentration in pCi/L, plus an explanation of what the result means for your specific situation.
Homeowners sometimes ask about hardware store test kits. They are a reasonable screening tool for a house you already live in, and county health departments in NJ sometimes offer free kits during Radon Action Month in January. For a real estate transaction, though, a professionally conducted test with a continuous monitor is the standard, because both sides of the deal need results they can trust.
Short Term vs. Long Term Radon Testing
| Factor | Short Term Test | Long Term Test |
| Duration | 48 hours to 90 days, typically 2 to 4 days | More than 90 days, often a full year |
| Best for | Home purchases and quick answers | Understanding true year round average exposure |
| Accuracy | Snapshot that can be influenced by weather and season | Most accurate picture of long term exposure |
| When we recommend it | Every real estate transaction in Central Jersey | Homeowners with borderline results between 2 and 4 pCi/L |
Radon levels naturally run higher in winter, when homes are sealed tight and heating systems pull soil gases inward. That is why the NJDEP calls the heating season the best time to test. If your home tested fine in July, a January retest is still worth doing at least once.
Radon Testing During a Home Sale in Middlesex County
For buyers, radon testing is one of the smartest add-ons to a home inspection in Edison, Metuchen, New Brunswick, or anywhere else in the county. The test runs during the inspection window, so results arrive in time to act on them. If levels come back at or above 4 pCi/L, you can typically negotiate for the seller to install a mitigation system or credit you the cost at closing. Mitigation systems in NJ generally run between about $800 and $2,500, which is a small number compared to the price of the house and a very solvable problem.
For sellers, testing before you list is a strategic move. New Jersey sellers are required to disclose known radon test results and any mitigation records to buyers. Finding out your number early means you control the timeline. If the result is elevated, you can install mitigation on your schedule and market the home with a documented fix in place, which reads as a positive to buyers rather than a red flag discovered mid-deal.
One more note for buyers of homes with existing mitigation systems in older towns like Milltown, Bound Brook, and Highland Park: a fan mounted on a pipe does not guarantee the system still works. Mitigation fans wear out after roughly 10 years. We verify with a fresh test, not a glance at the equipment.
What Happens If Your Radon Levels Come Back High?
First, do not panic, and do not walk away from a house you love over a radon number. Radon is one of the most fixable issues a home inspection can uncover. The standard solution is active sub-slab depressurization, which sounds complicated but is straightforward: a sealed pipe runs from beneath the foundation slab to the exterior, and a quiet inline fan continuously pulls soil gas out from under the house and vents it safely above the roofline before it can enter your living space.
A properly installed system routinely drops radon levels below 2 pCi/L, often below 1. In New Jersey, mitigation work must be performed by an NJDEP certified mitigation business, and the job is not done until a follow-up radon test confirms the system works. Always retest after installation, and keep the paperwork. Those records protect you at resale.
Why Radon Testing Belongs in Your Home Inspection Plan
A radon number tells you the concentration. A home inspection tells you the why. When I test a home in Old Bridge or Woodbridge, I am also looking at the conditions that influence radon entry and mitigation design: foundation cracks, sump pits without sealed lids, crawl spaces with exposed soil, French drain systems, and the layout of the basement. Those details matter if mitigation becomes necessary, and they are exactly what a thorough home inspector documents anyway.
That is why bundling radon testing with your home inspection makes practical sense. One appointment covers the structure, the systems, and the air your family will breathe, and the findings inform each other. At DGM Inspection, radon testing is available alongside our full residential inspections, commercial property inspections, and related environmental services like mold inspection, indoor air quality testing, and underground oil tank sweeps.
Local Radon Testing for Middlesex County and Central Jersey
DGM Inspection is based in Milltown and serves home buyers, sellers, and property owners throughout Middlesex County and Central New Jersey, including Edison, East Brunswick, Piscataway, Old Bridge, South Brunswick, Woodbridge, Metuchen, Sayreville, Monroe Township, New Brunswick, Highland Park, and Bound Brook. Every inspection and radon test is handled by Gregory Anzano, NJ licensed home inspector #24GI00201100. You get one experienced set of eyes on your property and a report written in plain language, not boilerplate.
Know Your Number Before You Buy, Sell, or RenovateWhether you are under contract on a home in East Brunswick, listing your house in Sayreville, or simply want peace of mind about the air in your basement, DGM Inspection makes radon testing in NJ simple and stress free. Book online at dgminspection.com or reach out through our contact page to schedule your radon test or full home inspection today. |
Frequently Asked Questions About Radon Testing in NJ
Is radon testing required in New Jersey?
Radon testing is not legally required for most residential sales in New Jersey, but sellers must disclose any known radon test results and mitigation records. In practice, most buyers include radon testing as part of their home inspection contingency, and lenders on certain loan types may require it. The NJDEP recommends that every home in the state be tested regardless of location.
What level of radon is dangerous?
There is no known fully safe level of radon. The EPA and NJDEP set the action level at 4.0 pCi/L, meaning mitigation is recommended at or above that concentration. The EPA also suggests considering mitigation for results between 2 and 4 pCi/L, since long term exposure at those levels still carries some risk.
How much does radon testing cost in NJ?
A professional radon test in Central Jersey typically costs between $100 and $200 when performed as a standalone service, and often less when bundled with a full home inspection. Considering that radon is the leading cause of lung cancer among nonsmokers, it is one of the most valuable line items in any inspection.
How long does a radon test take?
A short term radon test requires a minimum of 48 hours under closed house conditions. Most real estate radon tests run 2 to 4 days, which fits comfortably inside a standard inspection contingency window. Results are usually available within a day of the device being picked up.
Do new homes in New Jersey have radon problems?
They can. Radon comes from the soil beneath the home, not the age of the construction, and newer homes are often sealed more tightly, which can trap radon indoors. New construction in radon prone areas of NJ may include passive radon resistant features, but those still need to be tested and sometimes activated with a fan.
Does a finished basement make radon worse?
A finished basement does not create radon, but it changes the stakes. If your family spends real time in a finished basement in a town like Piscataway or Monroe Township, you are breathing the air at the lowest level of the home where radon concentrates. Testing before and after finishing a basement is a smart move.
Can I sell my house in NJ if it has high radon?
Yes. High radon does not block a sale, but you must disclose known results to buyers. Most sellers either install a mitigation system before listing or negotiate the cost during attorney review. A documented, tested mitigation system is generally viewed as a plus by informed buyers.
How often should I retest my home for radon?
Retest every 2 to 5 years, and always retest after major renovations, foundation work, new HVAC installation, or finishing a basement. If you have a mitigation system, test every 2 years to confirm the fan is still doing its job, since mitigation fans typically last about 10 years.