--- title: Do Radon Mitigation Systems Actually Work? canonical: "https://radonmitigationyorkpa.net/radon-guide/do-radon-mitigation-systems-work/" pubDate: "2026-10-01T00:00:00.000Z" updatedDate: "2026-10-03T00:18:00.000Z" author: Radon Mitigation York PA description: "Yes, radon systems work when installed right. See how much they lower radon, why some fall short, and how to make sure yours keeps working." --- # Do Radon Mitigation Systems Actually Work? Yes. A [well-installed radon mitigation system](/services/radon-mitigation-system-installation/) works very well when it is properly designed. The EPA lists active sub-slab depressurization, the most common type, as reducing indoor radon by 50 to 99 percent. Most homes can be brought below the EPA action level of 4.0 pCi/L. A clearance test after install shows whether your system is doing its job. ## How much radon do systems remove? The EPA's [Consumer's Guide to Radon Reduction](https://www.epa.gov/sites/default/files/2016-12/documents/2016_consumers_guide_to_radon_reduction.pdf) gives these typical ranges for common methods: | Method | Typical reduction (EPA) | |---|---| | Sub-slab depressurization (active) | 50 to 99 percent | | Sub-membrane depressurization (crawl space) | 50 to 99 percent | | Passive sub-slab suction (no fan) | 30 to 70 percent | | Drain tile or sump hole suction | 50 to 99 percent | | Sealing cracks alone | Not recommended alone; inconsistent results | The wide range comes from differences between houses. A home with loose gravel under the slab and few openings tends to land at the high end. A home with tight soil or a mix of foundations needs more design work to get there. For measured results from field studies, see our data on [radon levels before and after mitigation](/radon-guide/radon-levels-before-and-after-mitigation/). ## Why they work Radon comes from the soil under your house. A radon system does not try to clean the air in your rooms. It goes to the source. A fan pulls on a pipe sealed into the soil under your slab. That makes the soil under your home lower in pressure than the house above it. Soil gas, including radon, is drawn into the pipe and vented above the roof instead of seeping up through the floor. As long as the fan runs, the pressure stays reversed. ## Why some systems fall short When a system does not bring radon down enough, it is almost always for one of these reasons. ### Poor suction point placement If the suction point is in a corner or far from where radon is entering, the suction may not reach the whole slab. A pre-install diagnostic test helps place it well. ### The wrong fan A fan that is too weak for the soil under your home will not spread suction far enough. Fans come in a range of sizes for different conditions. For a look at models and how they differ, see [radon fans compared](/radon-guide/best-radon-fan/). ### Missed foundation areas A basement with a crawl space addition, a slab-on-grade room or a stone section may need more than one suction point. If one area is left out, radon keeps coming in there. ### Unsealed openings An open sump pit or large cracks let the fan pull basement air instead of soil gas. That weakens suction under the rest of the floor. ### The fan stopped Fans run 24 hours a day and wear out eventually. A switched-off fan, a tripped outlet or a failed motor turns an active system into a passive one, and radon levels rise again. ## How to know your system is working ### The clearance test EPA guidance says to test no sooner than 24 hours after the system starts and within 30 days. This shows your new radon level and is the real proof the system works. ### The manometer Every active system in Pennsylvania needs a gauge you can easily read. On most systems it is a U-tube on the pipe. Uneven liquid levels mean the fan is pulling. Level liquid means it is not. ### Retesting over time The EPA suggests retesting at least every two years. Also retest after a big remodel, a new addition or a finished basement project. ## What about passive systems? Some newer homes have a passive pipe built in, with no fan. These rely on natural airflow from warm air rising through the pipe. The EPA lists passive sub-slab suction at 30 to 70 percent reduction, well below an active system. If a passive system's test result is still high, adding a fan is usually the next step. ## What makes a system work in York homes York County is in EPA Radon Zone 1, the highest potential zone. Many local homes also have features that make design more important: - **Older stone foundations.** Fieldstone and rubble walls have many gaps and may need extra sealing or wall suction. - **Mixed foundations.** Additions on crawl spaces or slabs are common and may need their own suction. - **Sump pits.** Many basements have them, and they can serve as good suction points when sealed. A certified installer who has worked in local homes knows to look for these. In Pennsylvania, anyone who mitigates radon for others must be certified by PA DEP. ## Key takeaways - Radon systems work. The EPA lists sub-slab depressurization at 50 to 99 percent reduction. - Most homes can be brought below 4.0 pCi/L with a well-designed system. - Shortfalls usually come from poor placement, a weak fan, missed areas or unsealed openings. - A clearance test, the manometer and regular retesting confirm it keeps working. - Passive systems are weaker than active ones and often need a fan added. ## Frequently Asked Questions ### Can a radon system get my level to zero? Not usually. Outdoor air has some radon too. The goal is to get as low as practical, below 4.0 pCi/L and ideally below 2. ### How long does a radon system last? The pipe can last as long as the house. The fan is the part that wears out and eventually needs replacing. ### Does a radon system work right away? Levels begin dropping within hours of the fan starting. The clearance test after at least 24 hours confirms the result. ## Get a system built to pass We design each system around your home and back it with a written clearance guarantee. Call [(717) 356-3035](tel:+17173563035) any time for a free written quote and a same-day callback.