Post-Mitigation Radon Retest in Eau Claire, WI
Every mitigation install ends with a post-mitigation retest. The retest is a short-term radon test run with the new system on, under the same closed-house protocol used for the original test. It's the only way to confirm the system actually fixed the problem.
Protocol
- Wait 24 hours after the mitigation fan is energized.
- Place a sealed canister or CRM on the lowest livable level.
- Run the test for 48–96 hours under closed-house protocol.
- Lab analyzes the canister, or the CRM uploads its log.
- Written report sent to the homeowner.
What "passing" looks like
A post-mitigation reading below 4.0 pCi/L is the EPA's threshold for a passed retest. In practice most installs in the Chippewa Valley land below 1.5 pCi/L. A reading above 4.0 pCi/L is unusual and indicates the suction is undersized for the slab or there are major air-loss paths still open — fixed under warranty.
When to retest beyond the install
- Every two years after the install (EPA guidance).
- After any major renovation, especially basement finishing.
- After any HVAC system change.
- After a new mitigation fan is installed in an existing system — see radon system inspection.
- If the manometer ever reads level — that means the fan is off or the pipe is blocked.
Need a radon test or mitigation system in the Chippewa Valley?
Same-week appointments are typical. Real-estate-deadline tests can usually be slotted in 24–48 hours.
Frequently asked questions
When does the retest happen?
The retest starts at least 24 hours after the mitigation fan is energized, to give the system time to draw down soil gas under the slab. Most retests run for 48 hours of closed-house data, with results back the following business day.
What if the retest still reads above 4 pCi/L?
Common fixes are additional sealing of slab penetrations, a larger fan, or a second suction point on the opposite side of the basement. These adjustments are typically covered under the workmanship warranty — re-installs continue until the home tests below 4.0 pCi/L.
Is a retest required?
Yes, per ANSI/AARST standards. Real-estate transactions also typically require a post-mitigation retest as documentation that the system actually solved the problem, not just that a system was installed.
How often should the system be re-tested after that?
EPA recommends a follow-up test every two years, or any time there's been a significant change to the home (renovation, HVAC swap, new windows). Annual checks of the manometer reading are the homeowner's responsibility — five seconds, just walk past the riser and verify the fluid is offset.
Other radon services
New homeowner who needs a baseline test? See radon testing. Buying or selling? See real estate radon test.