A Practical Guide for Realtors, NH Homeowners, Prospective Home Buyers, and Prospective Home Sellers

Radon is a naturally occurring radioactive gas that forms from the breakdown of uranium in soil and rock. It has no smell, taste, or color, so testing is the only way to know if it is present. Radon exposure is a serious health concern and is the second leading cause of lung cancer in the United States.

New Hampshire has higher radon levels than many states due to its geology, making radon testing especially important during real estate transactions. Below, we are going to answer the questions we get most frequently: What is the radon limit in NH? Is radon a problem in NH? What is a safe or acceptable radon level in New Hampshire?

🏠 Radon in Air: What Realtors Need to Know

No National Law Requires Action

There are no federal or New Hampshire laws requiring homeowners to mitigate radon, even if elevated levels are found. However, radon is widely recognized as a health risk, and action is strongly encouraged based on testing results.

EPA Recommended Action Levels for Radon in Air

The U.S. Environmental Protection Agency (EPA) provides the following guidance:

• 4.0 pCi/L or higher
  The EPA recommends mitigation at this level or above.

• Between 2.0 and 4.0 pCi/L
  The EPA recommends considering mitigation, particularly in high-radon states like New Hampshire.

• Below 2.0 pCi/L
  Radon risk is lower, but no level of radon is completely risk-free.

Helpful context:

• Average indoor radon level in the U.S.: ~1.3 pCi/L

• Many homes in NH test above 4.0 pCi/L

💧 Radon in Water: New Hampshire Guidance vs. EPA Recommendations

Radon can also be present in private well water. While ingesting radon in water is a concern, the primary risk is radon released into the air when water is used for showering, washing dishes, or laundry.

No Enforceable Federal Standard

There is no federally enforced limit for radon in private well water. The EPA has issued guidance, but it is not a law.

EPA Recommended Level (Reference Point)

• 4,000 pCi/L
  This is the EPA’s proposed alternate maximum contaminant level for public water systems. It is commonly used as a general reference point, even though it does not apply to private wells.

✅ New Hampshire–Specific Radon in Water Guidance

New Hampshire evaluates radon in water in combination with radon in air, which provides a more accurate assessment of overall risk.

Recommended Action Levels in NH

• Above 2,000 pCi/L
  If indoor air radon levels exceed 4.0 pCi/L, treatment of water may be recommended.

• 10,000 pCi/L or higher
  If indoor air radon levels are low, water treatment may still be recommended at this higher threshold.

This approach recognizes that water radon contributes to air radon, and mitigation decisions should consider both results together.

🧠 Talking Points for Realtors

• Radon testing is the only way to know if radon is present.

• There is no legal requirement to fix radon, but EPA and NH health agencies provide clear guidance.

• Elevated radon levels are common in New Hampshire and do not mean a home is unsafe or unsellable.

• Radon mitigation systems for air and water are effective and widely available.

• Understanding these thresholds helps buyers make informed, confident decisions.

📊 Quick Reference Table

🧩 Final Takeaways

• No federal or NH laws require radon mitigation, but strong health-based recommendations exist.

• EPA action level for air: 4.0 pCi/L

• NH water guidance: depends on indoor air radon levels

• Testing supports transparency, safety, and smoother real estate transactions.