Is Missouri a high radon state?
Missouri DHSS reports radon in every county. That includes Jefferson County, but a state description does not establish the concentration in an Arnold or Festus home. Use the actual property’s test report to decide what to investigate.
If you have no report, begin with measurement. If you already have a result, send the complete document so its location, dates and test method can be reviewed. County-level evidence is background information, not a diagnosis for an individual address.
What Jefferson County homes are most likely to have radon?
Appearance and house age cannot reliably identify which property will test high. A crawl space or combination foundation is a detail to assess, not a reason to assume a particular result. The same is true of a ranch or split-level design.
Walk through the lowest level and note where additions meet the original house. An enclosed porch, expanded bedroom or attached space may have a different foundation beneath it. Explain those transitions even when the finished rooms make the house appear continuous.
- Identify the original foundation.
- Mark additions and crawl spaces.
- Share every available test report.
How is radon mitigated in a split-level or combination foundation?
The design needs to address the relevant foundation sections. A proposal should explain how the basement, separate slabs and any crawl space will be considered together. Do not assume a collection point serving one portion also serves every addition.
For a Jefferson County house with limited crawl access, tell the provider about the opening and clearance. Photos and a simple sketch can help prepare for the visit. Avoid entering a difficult crawl space just to gather estimate photos.
- Show each floor elevation.
- Identify crawl-space access.
- Ask how the whole layout is assessed.
- Agree on post-installation verification.
What does radon mitigation cost in Jefferson County?
Air Sense publishes $1,100 to $3,200 for a standard active sub-slab system. A crawl-space membrane or mixed-foundation project requires an address-specific scope. Do not treat the standard range as a ceiling for work that has not been inspected.
Ask what the estimate includes and whether access preparation is needed. The written proposal should distinguish installation, electrical arrangements, testing and any restoration work.
Communities we serve
Air Sense Environmental handles inquiries for Jefferson County and nearby south St. Louis County. Provide the address to confirm the visit and scope, particularly for Hillsboro or De Soto. These community references do not represent branch offices.
- Arnold, Imperial and Barnhart
- Festus and Crystal City
- Hillsboro and De Soto
- Oakville and Mehlville in south St. Louis County
What Air Sense customers say
Excerpts from Google reviews of Air Sense Environmental, quoted as written. Reviewer names are withheld; each link opens the full review on Google. These customers are from across the St. Louis area, not only this county.
“We had another bid previously from a different company who told us our home would be difficult, and he really did not want to discuss solutions to making a system look nice. Jake was reassuring from the beginning.”
Google review, February 2026 · Read the full review on Google
“Jake was super professional and was able to make a difficult install look very easy!”
Google review, June 2025 · Read the full review on Google
“As soon as he arrived, he quickly assessed the best place to put the radon pipe (extra bonus, it is hidden from the street)”
Google review, May 2025 · Read the full review on Google
See all 167 Google reviews of Air Sense Environmental (rated 5.0 as of October 10, 2026)
Questions before you book
Does a crawl space need a different approach from a slab?
It may. Show the contractor the entire layout and ask whether a membrane and separate collection arrangement should be evaluated.
Do you offer well-water radon treatment?
This site covers indoor-air radon questions. Do not assume a quote for an air system includes testing or treatment of well water.
What should I do before an estimate?
Gather the test report, make a simple foundation sketch and photograph accessible equipment. Include the address and any timing requirements.