Radon is a colorless, odorless gas that slips through foundation cracks and piles up inside houses. For many homeowners the first confrontation with radon comes not from a visible problem but from a test result: a number in picocuries per liter, or pCi/L. That number matters because long-term exposure to elevated radon increases the risk of lung cancer. Interpreting that number, deciding whether to act, and choosing the right mitigation approach are practical tasks that reward careful judgment.
I write from years of inspecting homes, working with radon mitigation contractors, and seeing what succeeds and what doesn't. Below I’ll walk through how to read a radon test report, how to decide whether mitigation is needed, the types of radon systems available, what to expect during installation and afterward, and how to pick a contractor near you — with specific relevance for homeowners in St. Louis and similar climates.
How to read your radon test result
Most radon tests report average radon concentration in pCi/L. Short-term tests (two to seven days) and long-term tests (90 days to a year) are both common. Short-term tests are useful for quick screening, long-term tests give a better estimate of year-round exposure because they average seasonal and daily fluctuations.
If your short-term test reads below 2 pCi/L, the Environmental Protection Agency recommends no immediate action in most cases. Results between 2 and 4 pCi/L represent a gray area where mitigation is advisable depending on other factors, such as how often the lowest occupied level is used and whether you have children or smokers in the household. A reading at or above 4 pCi/L is the EPA action level, where mitigation is recommended. Keep in mind that these are guidelines, not laws; many public health agencies recommend taking action at lower levels, especially when children are involved.
A few practical points about test variability and what that number actually means: indoor radon fluctuates with weather, stack effect, HVAC cycles, and occupant behavior. A winter test with windows closed often shows higher values than a summer test with windows open. Short-term tests can vary substantially; two consecutive short-term tests in the same house can differ by 1 to 3 pCi/L or more. That makes confirmatory testing important when results hover near decision thresholds.
When to retest, and which test to choose
If you get a single short-term result above 4 pCi/L, run a follow-up test before scheduling mitigation, unless you have a clear reason to act immediately. Follow-ups can be either a second short-term test run immediately after the first, or a long-term test that covers fall and winter months to get a seasonal average. For buyers and sellers, the usual protocol is a continuous monitor or two short-term tests back-to-back; it's common to see closing contingencies tied to a retest within a specified timeframe.
Long-term testing is preferable when you have time and want a robust basis for decision-making. Long-term tests reduce the chance of a false positive caused by a temporary pressure condition. If the average over three months is above 4 pCi/L, you should plan mitigation. If results are inconsistent, err on the side of caution — radon risks accumulate over years.
What mitigation aims to do
A radon mitigation system's job is straightforward: reduce indoor radon concentrations to a level that significantly lowers long-term health risk. That usually means reducing basement or lowest-occupied-level radon to under 4 pCi/L and often to 2 pCi/L or below. The most common solution is active soil depressurization, which alters pressure beneath the slab or under a crawlspace vapor barrier so radon is drawn outside instead of into living space.
Mitigation is not a one-size-fits-all product. Effective design depends on foundation type, soil porosity, presence of a sump, crawlspace height, and mechanical systems in the house. A high-quality system will include a properly sized fan, sealed connections, a visible manometer or pressure gauge so occupants can tell the system is working, and clearly routed exhaust piping that discharges above the roofline and away from vents or windows.
Common radon system types and how they work
Active sub-slab depressurization, also called a radon mitigation system, is the approach used in most slab-on-grade and basement houses. The contractor drills a suction pit into the slab or connects to an existing sump, installs piping, and places a continuously operating fan that vents soil gas outdoors. The fan creates lower pressure beneath the slab than inside the house, preventing radon from being pulled indoors.
Crawlspace ventilation and encapsulation are typical for homes with crawlspaces. Some systems use a combination of a vapor barrier covering the soil with perimeter sealing, a small fan-driven suction point, and improving ventilation to lower soil gas entry. In humid climates additional moisture control is essential to avoid mold problems.
For houses with block walls or large cracks, specialized techniques like block-wall depressurization — where suction points are placed in the hollow cores of concrete block walls — can be effective. Manufactured homes, basements with poured footings, and houses built on radon-prone soils may require hybrid strategies. Each structure invites trade-offs; for example, increasing ventilation can reduce radon but may raise energy costs and bring in outdoor pollutants.
Costs and expected performance
On average, professionally installed mitigation systems in single-family homes usually cost several hundred to a few thousand dollars, depending on complexity. In many places, a basic active soil depressurization system is in the $800 to $2,500 range, while more elaborate installations involving crawlspace encapsulation or modifications to complex foundations can run higher. If you live in the St. Louis area, pricing is similar to other Midwestern markets, though labor and permit costs vary.
A properly installed and commissioned system typically reduces indoor radon levels by 50 to 99 percent. For a house reading 8 pCi/L, a competent mitigation system should commonly bring levels below 2 pCi/L, though a precise outcome cannot be guaranteed until after installation and follow-up testing. Mitigation reduces risk substantially, and industry experience shows that systems maintained and monitored over time continue to hold radon levels down.
What to expect during installation
A standard installation takes three to eight hours in most homes. The contractor will identify the best suction point, drill through the slab or tap into existing open spaces, install PVC piping that routes vertically and then through the roof or side wall, and mount the fan in an exterior-friendly location or inline in the attic. Pipes should be labeled and fastened to avoid vibration or noise transfer.
Sealing foundation penetrations and large gaps is part of the work, but sealing alone rarely removes the need for active mitigation. The installer should show you a manometer or digital monitor that indicates the system is operating and explain where the exhaust terminates. After installation, the house should be tested again. Short-term post-mitigation testing is common for initial verification, followed by long-term monitoring if needed.
Maintenance considerations and lifespan
Fans used in radon systems are mechanical devices with expected lifespans of roughly five to 10 years depending on model and duty cycle. Choose a system with an accessible, replaceable fan. Inspect the manometer monthly; a steady reading indicates continuous operation. If you notice a sudden jump in indoor radon, the first check is whether the fan is running.
Roof penetrations and piping need occasional visual inspection. If you have a sump-connected system, make sure sump covers remain sealed and intact. If you renovate a basement, mention the radon system to your contractor because work that alters the slab or ventilation paths can affect performance.
When to call a contractor back
Re-evaluate if you renovate, install a new HVAC system, or change major airflow patterns in the house. Also retest if the fan fails, if the manometer shows loss of suction, or if occupants report consistent new symptoms that suggest indoor air problems. Annual or biennial testing gives simple assurance the system is still performing.
Picking a mitigation contractor — what to ask and look for
Experience varies widely among contractors. Ask for references and recent examples of work in homes similar to yours. A good contractor will evaluate foundation type and soil conditions before recommending a specific system and will explain trade-offs honest and plainly. Avoid contractors who promise guaranteed numbers without a site evaluation.
If you live in the St. Louis region and search for "Radon mitigation St Louis" or "Stl Radon," expect several local contractors with certification through organizations like the National Radon Proficiency Program or state licensing bodies. Certification and insurance matter. A contractor should provide a written proposal that explains location of suction points, fan model and placement, pipe routing, monitoring method, warranty on workmanship, and expected reduction range based on similar homes they have mitigated.
Use this short checklist when calling contractors
- confirm they have radon mitigation certification and insurance ask for 3 references from recent jobs in similar homes request a written scope, fan model, and warranty details verify they perform post-installation testing check whether they handle permits if required
Negotiating price and scope
Low bids may cut corners, using undersized fans or routing exhaust below roofline where it can re-enter the structure. High bids may include unnecessary options. Evaluate proposals for clarity and completeness rather than choosing solely on lowest price. Pay attention to whether the contractor includes testing, permits, and a guarantee of performance. A contract that includes follow-up testing and a short operational warranty on the fan offers useful protection.
A real-world anecdote about performance
I once saw a 1950s bungalow in a St. Louis neighborhood with a finished basement used as a family room. The initial short-term test read 12 pCi/L. The homeowner hired a local mitigation contractor who installed an active sub-slab system routed through the attic and out the roof. After installation the homeowner retested with a continuous monitor and saw readings between 1 and 1.8 pCi/L over several weeks. The fan was slightly undersized for the soil conditions, so they upgraded to a larger unit. The revised system stabilized at 0.9 pCi/L. That case shows two things: first, the difference an experienced installer can make; second, that a bit of follow-up and willingness to adjust equipment can produce excellent results.
Special cases and edge conditions
Homes with complicated foundation geometries, large stone foundations, or extensive perimeter drains can be harder to mitigate. Manufactured homes require strategies that address the underbelly and skirting. Sump-connected systems Radon mitigation system sometimes lose effectiveness if the sump gets clogged. In houses where radon is unusually high, contractors may combine sub-slab depressurization with crawlspace improvements or make additional suction points. Be wary of promises that sound too simple for complicated foundations — the soil and air pathways under a house are invisible and often more complex than they look.
Radon in real estate transactions
Buyers often ask whether they should proceed if a home tests above 4 pCi/L. Many sellers choose to install a mitigation system prior to closing to remove uncertainty and to meet inspection contingencies. Buyers may negotiate repairs or credits for mitigation. If you are a buyer in St. Louis, understand local market practice. In some neighborhoods sellers install and provide a post-mitigation test; in others the buyer arranges mitigation after closing. Regardless, require documentation of what was installed and that post-mitigation testing shows acceptable levels.
DIY testing and when to hire a pro
Homeowners can buy accurate short-term test kits and send them to certified labs. For a dependable screening, use a continuous digital monitor that logs hourly data, which is especially useful if you want to understand how daily activities affect levels. However, mitigation design and installation are technical trades. Unless you have experience with structural penetrations, fan selection, and HVAC interactions, hiring an experienced radon mitigation contractor is usually the wiser route. Incorrectly installed systems can underperform and, in a worst case, create other building problems.
Final checks after mitigation
Once your system is installed, perform a post-mitigation test. Expect the contractor to either perform the test or recommend an independent tester. If the post-mitigation level fails to meet targets, discuss adjustment options with the contractor, such as increasing fan capacity, adding another suction point, or improving seals. Plan for future testing every two years, and sooner if you change the house’s airflow configuration.
Resources and local searches
When looking for "Radon mitigation near me" or "Radon mitigation contractor," check for certification and ask for recent job references. Local public health departments often provide lists of certified testers and contractors. For homeowners in St. Louis, local radon programs and building departments can advise on permitting and contractors familiar with St louis radon conditions and soils. Ask potential contractors if they are familiar with typical radon levels in your county and whether they have experience with houses like yours.
A closing practical note, from experience
Radon mitigation is rarely glamorous, but it is straightforward and impactful. The decisions take place on a pragmatic timeline: test, confirm, design, install, verify. Expect clear, sometimes noisy equipment running continuously, a modest hit to your utility bill if you increase ventilation, and, with a competent system, a large reduction in long-term health risk. When you choose contractors thoughtfully, require testing, and keep basic maintenance, a radon system becomes an ordinary part of home upkeep rather than a persistent worry.
Air Sense Environmental – Radon Mitigation & Testing
Business Name: Air Sense Environmental – Radon Mitigation & TestingAddress: 5237 Old Alton Edwardsville Rd, Edwardsville, IL 62025, United States
Phone: (618) 556-4774
Website: https://www.airsenseenvironmental.com/
Hours:
Monday: 9:00 AM – 5:00 PM
Tuesday: 9:00 AM – 5:00 PM
Wednesday: 9:00 AM – 5:00 PM
Thursday: 9:00 AM – 5:00 PM
Friday: 9:00 AM – 5:00 PM
Saturday: Closed
Sunday: Closed
Plus Code: RXMJ+98 Edwardsville, Illinois
Google Maps URL: https://maps.app.goo.gl/XTPhHjJpogDFN9va8
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Popular Questions About Air Sense Environmental – Radon Mitigation & Testing
What services does Air Sense Environmental provide?
Air Sense Environmental provides professional radon testing, radon mitigation system installation, indoor air quality solutions, and crawl space encapsulation services in Edwardsville, Illinois and surrounding areas.Why is radon testing important in Illinois homes?
Radon is an odorless and invisible radioactive gas that can accumulate indoors. Testing is the only way to determine radon levels and protect your household from long-term exposure risks.How long does a professional radon test take?
Professional radon testing typically runs for a minimum of 48 hours using continuous monitoring equipment to ensure accurate results.What is a radon mitigation system?
A radon mitigation system is a professionally installed ventilation system that reduces indoor radon levels by safely venting the gas outside the home.How do I contact Air Sense Environmental?
You can call (618) 556-4774, visit https://www.airsenseenvironmental.com/, or view directions at https://maps.app.goo.gl/XTPhHjJpogDFN9va8 to schedule service.Landmarks Near Edwardsville, IL
Southern Illinois University Edwardsville (SIUE)A major public university campus that serves as a cultural and educational hub for the Edwardsville community.
The Wildey Theatre
A historic downtown venue hosting concerts, films, and live entertainment throughout the year.
Watershed Nature Center
A scenic preserve offering walking trails, environmental education, and family-friendly outdoor experiences.
Edwardsville City Park
A popular local park featuring walking paths, sports facilities, and community events.
Madison County Transit Trails
An extensive regional trail system ideal for biking and walking across the Metro East area.
If you live near these Edwardsville landmarks and need professional radon testing or mitigation, contact Air Sense Environmental at (618) 556-4774 or visit https://www.airsenseenvironmental.com/.