Blog › 2026-10-21
Radon Tests When Buying or Selling a Home in Greenville
Radon has become a routine line item in Upstate home inspections. With Greenville County listed in EPA Radon Zone 1, buyers and their agents ask about it more and more. Here's how it usually plays out, and how to keep it from derailing a closing.
For buyers
Ask first
Ask the seller whether the home has been tested or already has a mitigation system. If there's a system, look for the manometer (a U-tube gauge on the pipe) and ask for any post-mitigation test results.
Test during your inspection window
EPA's Home Buyer's and Seller's Guide to Radon recommends testing if the home hasn't been tested, or wasn't tested in the lowest livable level. A short-term test of at least 48 hours with a continuous monitor is the common real-estate choice, because it gives results fast and records hourly data that can flag disturbances. Book it early, since a 48-hour test plus reporting has to fit inside your due-diligence period.
If the result is 4 pCi/L or higher
- Common options include asking the seller to install a system before closing, asking for a credit, or splitting the cost.
- Learn how mitigation systems work so you know what you are looking at.
- If the seller installs it, ask for the installer's details and a post-mitigation test result.
- Get a written mitigation quote quickly so everyone is negotiating from a real number. See typical mitigation costs.
New construction
Buying a new home in a Greer or Simpsonville subdivision? Ask whether it was built with radon-resistant features. Either way, EPA recommends testing new homes too.
For sellers
Consider testing before you list
Finding out up front lets you decide on your own timeline rather than under a buyer's deadline. If the number is high, a mitigation system is a common one-day repair, and a low post-mitigation result is a selling point.
Keep test conditions honest
EPA guidance for real-estate testing emphasizes closed-house conditions and non-interference: windows and exterior doors closed except for normal entry, no fans pulling in outside air, and nobody moving the device. Continuous monitors can detect unusual swings, and tampering can sour a deal fast.
Have your paperwork ready
If the home already has a system, gather the install date, installer information, fan warranty and the most recent test result.
Timeline cheat sheet
| When | What |
|---|---|
| Day 1 of inspection period | Schedule a radon test alongside the home inspection |
| Days 1 to 3 | Test runs (at least 48 hours, closed-house conditions) |
| Day 3 to 4 | Results; if 4 pCi/L or higher, request a mitigation quote |
| Before closing | System installed; post-mitigation test (run at least 24 hours after the system starts) |
Actual deadlines depend on your contract. Check with your agent.
Need it fast?
We work around inspection deadlines across Greenville, Greer, Simpsonville and the Upstate. Book radon testing, or request a radon mitigation quote and mention your closing date.
Reference: EPA, Home Buyer's and Seller's Guide to Radon.
Quick answers
How long does a real estate radon test take?
Typically at least 48 hours with a continuous monitor under closed-house conditions, plus time for the report.
Who pays for radon mitigation in a home sale?
It's negotiable. Sellers may install a system, give a credit, or split the cost with the buyer. Check with your agent.