Guides
Radon guides
What radon is, how to test, what the numbers mean, and how homes are fixed. Written from EPA, CDC, and state health-department sources.
Radon basics
What is radon, and how does it get into homes?
Radon is a radioactive gas from uranium in soil and rock. Here is where it comes from, how it enters a house, and why levels vary so much.
Read the guide →Radon health risks: what the evidence says
Why EPA ranks radon as the second leading cause of lung cancer, how smoking multiplies the risk, and what the numbers do and do not mean.
Read the guide →Radon in well water
How radon gets into private well water, why the main risk is breathing it after it escapes indoors, and how to test and treat.
Read the guide →The EPA radon zone map, explained
What EPA's 1993 Map of Radon Zones measures, how the three zones were set, its limits, and how to use it well.
Read the guide →Radon myths and facts
Common misconceptions about radon, from 'only old houses' to granite countertops, checked against EPA guidance.
Read the guide →Radon and smoking: why the combination multiplies lung cancer risk
EPA's numbers on how smoking and radon together raise lung cancer risk, what that means for smokers, former smokers and households with secondhand smoke, and the two most effective ways to cut the risk.
Read the guide →Do granite countertops give off radon? What EPA says and what actually matters
Whether granite and other stone countertops are a meaningful radon source, what EPA says about testing countertops, why soil gas is the main concern, and how to check your home if you're worried.
Read the guide →Radon glossary: 40 terms from action level to working level, explained plainly
Plain-English definitions of the radon terms you'll see in test reports, contractor proposals and EPA guidance, from pCi/L and Bq/m³ to sub-slab depressurization, manometers, closed-house conditions and RRNC.
Read the guide →Testing
How to test your home for radon
Where to put a test kit, how long to leave it, closed-house conditions, and how to avoid the mistakes that spoil results.
Read the guide →Short-term vs long-term radon tests
How short-term and long-term radon tests differ, which devices are used, and how to combine them before deciding on a fix.
Read the guide →Understanding your radon test results: pCi/L, Bq/m³, action levels and next steps
How to read a radon lab report, what pCi/L and Bq/m³ mean, how EPA's 4 and 2 pCi/L levels compare with international guidelines, how to handle conflicting results, and exactly what to do next at each level.
Read the guide →Why radon levels change with the seasons, weather and time of day
How the stack effect, wind, rain, frozen ground, barometric pressure and HVAC use make indoor radon rise and fall, why winter tests often read higher, and how to test so seasonal swings don't mislead you.
Read the guide →Radon in condos and townhomes: who should test, who fixes it, and how HOAs handle it
Which condo and townhome units are most likely to have radon, how to test when you share walls and foundations, why mitigation often needs the association's involvement, and how to raise the issue with your HOA.
Read the guide →Radon in manufactured and mobile homes: testing, skirting, crawl spaces and fixes
Why manufactured homes can still have radon, how skirting and the space beneath the home affect levels, how to test correctly, and the mitigation approaches that work for homes on piers and crawl spaces.
Read the guide →Fixing radon
How radon mitigation systems work
Sub-slab depressurization and other radon reduction methods explained, what installation involves, and how to check a system is working.
Read the guide →Radon-resistant new construction
The basic features of radon-resistant new construction, why they cost less during building, and how to activate the system if needed.
Read the guide →How to hire a radon mitigation contractor: credentials, bids and the contract
How to check a radon contractor's credentials, what a good estimate includes, the questions to ask, and what EPA says belongs in the contract before any work starts.
Read the guide →Living with a radon mitigation system: the manometer, the fan and retesting
How to read the U-tube manometer, what to do if it reads zero, how long radon fans last, when to retest, and how remodeling or selling affects your system.
Read the guide →Radon in crawl space homes: submembrane suction, ventilation and what works best
How radon enters homes built over crawl spaces, why EPA calls submembrane suction the most effective fix, how crawl space ventilation and depressurization compare, and what to ask a contractor.
Read the guide →Can you fix radon by sealing cracks? What DIY steps help, and what doesn't
Why EPA doesn't recommend sealing alone to reduce radon, how sealing supports a real mitigation system, which DIY steps are worthwhile, and when to call a qualified mitigator.
Read the guide →Radon in basements: testing, finished basements, bedrooms and fixing it
Why basements usually have the highest radon in a house, how to test a basement correctly, what finishing a basement means for radon, how sub-slab, drain tile, sump and block-wall suction work, and what to do before turning a basement into living space.
Read the guide →Radon and home renovations: when to test, what changes can raise levels, and how to plan
How remodeling, additions, new HVAC, window upgrades, energy-efficiency work and basement finishing can change radon levels, when to test before and after, and how to protect an existing mitigation system during construction.
Read the guide →Can ventilation reduce radon? HRVs, ERVs, fans and open windows compared
What EPA says about ventilation as a radon reduction method, how heat recovery ventilators work, why open windows and fans give only temporary relief, and when ventilation makes sense alongside soil suction.
Read the guide →Buying and selling
Radon when buying or selling a home
How radon testing fits into a home sale, which test options give fast results, and what buyers and sellers should ask.
Read the guide →Radon in rentals and apartments
Whether renters should test for radon, which apartments are most at risk, how to raise it with a landlord, and where state rules apply.
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