For most homes, fixing radon means a pipe and a fan that pull soil gas from under the house and send it out above the roof. EPA calls the usual version, active subslab suction, “the most common and usually the most reliable radon reduction method”.
This section follows the order most people need: confirm the number, learn what a system does, match the method to your foundation, rule out what doesn’t work, price the job, then choose who installs it.
Start with a number
A system is a fix for a measured result, so no fix comes before a test. You can’t borrow a neighbor’s result: EPA says levels “can vary greatly from home to home”. If you have no number yet, begin with how to test for radon.
With a number in hand, EPA’s Consumer’s Guide to Radon Reduction (2025 cover) gives the rule: “Fix your home if your radon level is confirmed to be 4 picocuries per liter, pCi/L, or higher.” Confirmed means one long-term test or the average of two short-term tests. Between 2 and 4, it says you “may want to consider fixing”.
EPA’s guides don’t all use the same verb. The Citizen’s Guide (2025 cover) says “fix” after a long-term test at 4 or more, but “consider fixing” after two short tests that average 4 or more. If you’re close to the line and have time, a long-term test gives a better picture before you spend the money.
Four pCi/L is a decision point, not a safety line. EPA says levels below it “still pose a risk, and in many cases may be reduced.”
What a system does
Air pressure in a house is usually lower than in the soil around it, so the home “acts like a vacuum”, drawing radon in through cracks and other openings. The fan makes the pressure under the floor lower than in the room above, so air at each crack moves down instead of up, and the soil gas goes to the pipe. How a radon mitigation system works walks through that physics and why the fan stays out of the living space.
If you want one page to read, make it the full guide to radon mitigation systems. It covers each part of a system, install day, how EPA’s checklist compares with the current standard, and what to put in a contract.
Match the method to your foundation
Your foundation decides most of this. These are the “typical radon reduction” ranges from the table in EPA’s Consumer’s Guide.
| Your home | Method | EPA typical reduction |
|---|---|---|
| Basement or slab | Active subslab suction | 50 to 99 percent |
| Drain tiles around the foundation | Drain-tile suction | 50 to 99 percent |
| Basement with a sump | Sump-hole suction | 50 to 99 percent |
| Hollow block walls | Block-wall suction, often added to subslab suction | 50 to 99 percent |
| Crawl space with an earth floor | Submembrane depressurization | 50 to 99 percent |
| Crawl space | Natural ventilation | 0 to 50 percent |
| New home built with a pipe and no fan | Passive subslab suction | 30 to 70 percent |
- Concrete floor. Sub-slab depressurization covers the layer under the concrete. EPA says “Often, only a single suction point is needed,” and that the number depends on how easily air moves under the slab and how strong the radon source is. The page shows how a contractor checks that, and what happens when sub-slab suction falls short.
- Crawl space. EPA calls submembrane suction, when properly applied, “the most effective way to reduce radon levels in crawlspace homes”. Radon in a crawl space explains what a good membrane job looks like, what to do when you can’t get in there, and why encapsulation with no suction isn’t a radon system. EPA says homes with mixed foundations may need a combination of methods.
- A pipe and no fan. Passive radon systems usually come with a new house. They usually lower radon, but in the largest capped-and-opened US study we found, about half the homes that started above 4 pCi/L stayed at 4 or above. Only a test tells you what yours does. At 4 or more, EPA says “you can have a qualified mitigator add a vent fan to an existing passive system”.
Treat “up to 99%” in sales talk with care. The phrase comes from EPA, which says “some” systems can reach it, and its range starts at 50. A percentage also depends on where you start, so the figure that counts is your level afterward. EPA’s Citizen’s Guide says “most homes today can be reduced to 2 pCi/L or below.” Only a follow-up test shows what your system did.
What doesn’t count as a fix
Sealing is the big one. EPA calls it “a basic part of most approaches to radon reduction”, but its Consumer’s Guide also says: “EPA does not recommend the use of sealing alone to reduce radon because, by itself, sealing has not been shown to lower radon levels significantly or consistently.” Does sealing concrete stop radon? goes through what the tests of sealers, paint and epoxy measured and where sealing is still worth doing.
Two more come up often. After you open windows, EPA says levels most often return to previous values within about 12 hours of closing up. And it says air cleaners without special media “will not remove gaseous pollutants, including radon”.
What it costs
EPA’s consumer guides print no installed price. Its cost answer says only that “Most homes can be fixed for about the same cost as other common home repairs.” We found no market survey, so the figures available are published estimates, and they disagree: Wisconsin (revised 21 October 2026) gives $1,000 to $2,000, Massachusetts (updated 7 October 2025) $1,200 to $2,000, and Minnesota an undated $1,500 to $3,000. None of these is a quote.
The radon mitigation cost calculator sets the published figures side by side and shows a worked estimate with every price and hour open to change. Its example, one suction point in a basement or slab home with 30 ft of pipe, comes to $1,361 to $1,470. A 1,000 sq ft crawl space in the same build-up comes to about $2,500 to $2,800. The hours and overhead in those totals are our assumptions, and permits and diagnostic tests aren’t included.
Massachusetts lists what moves a quote: home size, foundations, crawl spaces, floors, and how many suction points and fans the job needs. A fan drawing 72 watts uses about 631 kWh a year, about $115 at the EIA US residential average of 18.16 cents per kWh (August 2026, preliminary). That’s electricity only: EPA says most systems also cause some loss of heated or cooled air. The fan running cost calculator takes your own fan and rate.
Who does the work
EPA recommends a qualified contractor, because lowering high levels takes specific skills and without them “you could actually increase your radon level or create other potential hazards”. EPA certifies no one. It points to state processes and two privately run national programs, NRPP and NRSB. Your state radon office can tell you what your state asks for. Radon Handbook sells nothing and refers no one.
In most of the states we read, you can install a system in your own home without a license, though Illinois, Florida and New Hampshire aren’t clear. That exception doesn’t cover permits or wiring, and wiring belongs with a licensed electrician. DIY radon mitigation: what the rules allow gives the wording state by state, and what doing it yourself gives up.
After the install
The job isn’t finished until a test says so. EPA says to test within 30 days of installation, but no sooner than 24 hours after the system starts. It recommends an independent measurement, by a separate tester or by you. Then it says it’s a good idea to retest at least every two years, and after remodeling.
The fan stays on. EPA’s words: “the fan should NEVER be turned off; it must run continuously for the system to work correctly.” Our section on living with a system covers the fan, the gauge, the noise and the upkeep from there.
Your next step
For a number you already have, the radon test result reader gives EPA’s next step. If that step is a fix, EPA’s advice is “Get an estimate from one or more qualified radon mitigation contractors.” Ask each one:
- How many suction points do you plan, and why?
- Where will the fan and the exhaust go, and does that meet SGM-SF-2023, the current industry standard, and my state’s rules?
- What warning will I have besides the gauge, and will you mark the start-up reading?
- What level do you guarantee, for how long, and does it transfer if I sell?
- Who runs the test afterward, and how do I arrange an independent one?
This page is general information, not medical, engineering or legal advice.
Sources checked on 4 November 2026.
