Radon is the second leading cause of lung cancer in the United States — responsible for an estimated 21,000 deaths per year according to the EPA. It is colorless, odorless, and tasteless. You cannot detect it without a test. And New Jersey — particularly northern New Jersey — has some of the highest radon levels in the country.
If you are buying a home in New Jersey, radon testing is not optional. Here is what every buyer needs to know.
What Is Radon?
Radon is a naturally occurring radioactive gas produced by the decay of uranium in soil and rock. It seeps upward through the ground and enters buildings through foundation cracks, floor-wall joints, gaps around pipes, and any other openings where the building meets the soil. Once inside, it accumulates — particularly in basements and crawl spaces — and can reach concentrations that pose a serious long-term health risk to occupants.
Radon is measured in picocuries per liter of air (pCi/L). The EPA action level is 4.0 pCi/L — at or above this level, the EPA recommends mitigation. The EPA also recommends considering mitigation at levels between 2.0 and 4.0 pCi/L, as there is no truly “safe” level of radon exposure.
Why New Jersey Has Elevated Radon Risk
New Jersey’s geology — particularly in the northern and central counties — includes significant deposits of uranium-bearing rock and soil. The EPA classifies New Jersey into radon potential zones, and the majority of northern New Jersey falls into Zone 1 (highest potential, predicted average indoor radon above 4 pCi/L) or Zone 2 (moderate to high potential).
The counties with the highest radon potential in northern New Jersey include Morris, Sussex, Warren, Hunterdon, and Somerset. Bergen, Passaic, Essex, Union, and Middlesex counties also have elevated potential in many areas. Radon levels vary significantly even within a single neighborhood — the geology beneath one property may differ from the property next door.
This is why testing every home individually is the only reliable approach. County averages and neighborhood data cannot tell you what the radon level is in the specific home you are buying.
How Radon Enters a Home
Radon enters through any opening between the home and the soil:
- Cracks in concrete slab floors and foundation walls
- Construction joints where the floor meets the wall
- Gaps around service pipes and utilities
- Cavities within walls built on a slab
- Crawl space floors (dirt crawl spaces are particularly susceptible)
- Sump pits and floor drains
A home does not need cracks or visible defects to have elevated radon. Every home has some degree of contact with the soil, and radon will find its way in through even the smallest openings. New construction is not immune — Michael tests new construction homes regularly and elevated radon is found in them too.
How Radon Testing Works
Michael Del Greco is a licensed New Jersey Radon Measurement Technician (License #MET10521), a credential he has held since 1993 — the same year he founded Accurate Inspections. He uses a smart continuous radon monitor (CRM), which records radon levels at regular intervals throughout the test period and detects any tampering with closed-house conditions.
Here is exactly what the process involves:
Closed-House Conditions
New Jersey law (N.J.A.C. 7:28-27.2) requires closed-house conditions for at least 12 hours before the test begins and throughout the entire test period. Closed-house conditions mean all windows and exterior doors remain closed except for normal entry and exit. HVAC systems may operate normally. Whole-house fans and window fans must be off.
This requirement exists because opening windows artificially lowers radon readings — diluting the accumulated gas and producing a test result that does not reflect normal living conditions. A $125 retesting fee applies if closed-house conditions are not maintained during the test period. Michael explains these requirements clearly to all parties before the test is placed.
Placement
The monitor is placed in the lowest livable area of the home — typically the basement or first floor if there is no basement — as close to the center of the space as practical, away from exterior walls, windows, and HVAC supply or return vents.
Test Duration
The minimum test period under New Jersey regulations is 48 hours. Michael places the monitor at the start of the home inspection and returns personally to retrieve it after the test period is complete. The monitor data is uploaded to a certified laboratory, which issues an official result typically within hours of retrieval.
Results Delivery
Results are emailed to the buyer, the buyer’s attorney, and any other parties the buyer designates. The result is expressed as an average pCi/L over the test period.
What the Results Mean
The EPA’s guidance on radon test results:
- Below 2.0 pCi/L — the national average for indoor radon is approximately 1.3 pCi/L. Levels below 2.0 are generally considered acceptable, though the EPA notes that any radon exposure carries some risk
- 2.0 to 3.9 pCi/L — the EPA recommends considering mitigation. At these levels, long-term exposure represents a meaningful risk that mitigation can reduce significantly
- 4.0 pCi/L or above — the EPA action level. Mitigation is recommended. Most real estate contracts in New Jersey treat a result at or above 4.0 pCi/L as a condition requiring remediation
- 10.0 pCi/L or above — elevated levels that warrant prompt mitigation. Results at this level are not unusual in northern New Jersey’s high-radon geology
Radon Mitigation — What It Involves
If a test result comes back at or above the action level, radon mitigation is the solution. The most common and effective method is sub-slab depressurization (SSD) — also called active soil depressurization.
In a typical SSD system, a licensed radon mitigator installs a suction pipe through the foundation slab (or through the crawl space floor), connects it to a small fan, and vents the radon-laden soil gas to the exterior above the roofline. The system runs continuously and typically reduces indoor radon levels by 80 to 99 percent.
Radon mitigation is performed by licensed professionals. Immediate corrective actions are necessary when test results exceed the action level, and the scope and cost of mitigation should be determined by a licensed mitigator before the expiration of your inspection contingency. Mitigation costs vary based on the home’s foundation type and the complexity of the installation.
Once a system is installed, a post-mitigation test confirms the reduction. Mitigation systems require minimal maintenance — primarily annual fan checks — and are generally reliable for the life of the building.
Radon and Real Estate Transactions in NJ
In New Jersey real estate transactions, radon testing is typically conducted during the home inspection contingency period. When results come back at or above the action level, buyers have several options depending on the terms of their contract:
- Request that the seller install a radon mitigation system prior to closing
- Request a credit or price reduction to cover the cost of mitigation
- Install the system themselves after closing
- Withdraw from the contract if the contract terms permit
What the right approach is depends on the specific contract language and the buyer’s situation — a question for the buyer’s real estate attorney, not the home inspector. What Michael provides is the test result and the documentation. What happens next is a legal and negotiation matter.
Radon in Specific Northern NJ Counties
Morris County
Morris County has among the highest radon readings in New Jersey. The underlying geology — including significant gneiss and granite formations — is highly uranium-bearing. Michael strongly recommends radon testing for every Morris County property, regardless of age or construction type.
Sussex and Warren Counties
The northwestern counties of New Jersey are in a high-radon geological zone. Elevated readings are common, and many properties in these counties have had mitigation systems installed by prior owners — a system that should be tested to confirm it is still functioning effectively.
Bergen, Passaic, and Essex Counties
Radon levels vary within these counties depending on local geology. Some areas have consistently elevated readings; others are lower. There is enough variability that individual property testing remains the only reliable approach — county-level data cannot predict what any specific home will test.
Hudson and Middlesex Counties
These counties generally have lower average radon levels than the northwestern counties, but elevated results do occur — including in newer construction and in condominiums. Michael recommends testing for all of his clients regardless of county.
How to Add Radon Testing to Your Inspection
Radon testing is not included in the standard home inspection fee — it is a separate service added at the time of scheduling. Approximately 90% of Michael’s clients add radon testing, and he strongly recommends it for every property in northern New Jersey.
When you call to schedule, simply let the office know you would like to add radon testing. Michael will confirm pricing, explain the closed-house requirements to you, and coordinate the timing so the monitor is placed at the start of your inspection and retrieved after the required test period.
Call (973) 812-5100 between 8 AM and 8 PM on business days, or 8 AM to 5 PM on weekends.
Schedule Your NJ Home Inspection with Radon Testing
Accurate Inspections, Inc.
56 Woodland Drive, Woodland Park, NJ 07424
(973) 812-5100
Inspecting NJ Homes Since 1993 | NJ Licensed Home Inspector GI0121
NJ Radon Measurement Technician License #MET10521
