Radon Testing When Buying or Selling a Home

Radon has become a standard consideration in residential real estate. Whether you’re buying or selling, understanding how radon testing fits into the transaction protects both your health and your negotiating position.

Disclosure Laws

Radon disclosure requirements vary by state. Some states require sellers to disclose known radon test results and any mitigation history. Others have no specific radon disclosure law but include radon on general property disclosure forms. Regardless of state law, most real estate contracts give the buyer the right to conduct a radon test during the inspection period.

If you’re selling a home that has tested high in the past, proactive mitigation before listing can simplify the sale and avoid last-minute negotiations.

The 48-Hour Test Protocol

Real estate radon tests follow a specific protocol. A certified tester places a continuous radon monitor (CRM) in the lowest livable level of the home for a minimum of 48 hours. During the testing period, closed-building conditions must be maintained — all windows and exterior doors stay shut except for normal entry and exit. The HVAC system runs normally.

Tampering with the monitor or opening windows to artificially lower readings is detectable and can void the test. CRM devices log hourly data and often include motion and tilt sensors.

Negotiating Mitigation

If test results come back at or above the EPA action level of 4 pCi/L, buyers typically have three options: ask the seller to install a mitigation system before closing, negotiate a credit toward mitigation costs (usually $800 to $2,500), or walk away from the deal.

Most transactions settle on either seller-installed mitigation or a closing credit. Mitigation is straightforward and effective, so elevated radon rarely kills a deal — it’s simply a negotiation point.

Re-Testing After Mitigation

If a mitigation system is installed as part of the sale, a follow-up radon test should be conducted at least 24 hours after the system is operational. This confirms levels have dropped below 4 pCi/L. Buyers should also plan to retest every two years and after any significant foundation or HVAC changes.

For Sellers: Get Ahead of It

Testing before listing puts you in control. If levels are low, you have documentation to reassure buyers. If levels are high, you can install a system on your timeline and include it as a selling point. Either way, you avoid delays during the closing process.

Find certified radon testing professionals in your area to get ahead of the process.