How to Document Radon Mitigation for a Home Sale

The Complete Documentation Package

Assemble this before listing. Buyers, agents, and inspectors will ask for it:

1. Pre-mitigation test result

The original test that triggered mitigation. Shows you identified a real problem and addressed it responsibly. Buyers want to see that the system was installed for a reason, not randomly.

2. Post-mitigation test result

Confirms the system works. Should show a level well below the 4.0 pCi/L action level — ideally below 2.0 pCi/L. This is the most important document for buyers.

3. Installation documentation

• Contractor name, license number (NRPP cert # and state license if applicable), and contact info
• Installation date
• Fan model (RadonAway XP201, GX3 Pro, etc.)
• Suction point location(s)
• Post-installation vacuum reading (if provided)

4. Manometer photo

A current photo of the manometer showing differential pressure (one column lower than the other). This is instant visual confirmation the system is running. Buyers don't always know how to interpret the manometer — label the photo "System running normally."

5. Most recent retest results

Any biennial retests since the original post-mitigation test. A track record of consistent low levels over multiple years is the strongest possible documentation.

If You Don't Have Paperwork

If the system was installed before you owned the home, or if the original documentation is lost:

1. Identify the fan model: The model is printed on the fan housing. Photograph it.
2. Run a current test: A current long-term test is more valuable than missing historical records
3. Have the system inspected: An NRPP-certified contractor can inspect the system, document what's installed, and issue a written assessment — essentially creating current documentation

Buyers will feel better about a system with a current test and contractor inspection report than an older documented system with no recent confirmation.

What Buyers' Inspectors Check

During a home inspection, the inspector will typically:

• Note the presence of the radon system (pipe, fan, manometer)
• Read the manometer — confirm it shows differential pressure
• Ask for test documentation
• Recommend a buyer's radon test during the inspection period

If your manometer shows flat (equal columns), the fan has failed. Replace it before listing — a non-functioning radon system on an inspection report is worse than not having one.

Disclosure Requirements by State

Most states require disclosure of:

• Known radon test results (any result you have, even old ones)
• The presence of a mitigation system
• Known elevated radon without a mitigation system

States with mandatory disclosure: Pennsylvania, Colorado, Minnesota, Ohio, Illinois, Indiana, Iowa, and most others. Check your state's seller disclosure form — radon is typically a specific question.

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