NimbyCheck › Guides › Radon inside the home
Radon zones and why every home should test
What EPA radon zones mean for Massachusetts counties, why the map cannot rate a house, and how testing and mitigation work.
HealthGuidance reviewed 2026-09-13
A source is not an exposure measurement. Health effects depend on the chemical or physical agent, whether it reaches a person, its concentration, exposure route, duration and individual susceptibility.
Why living near radon inside the home may matter
Radon is a radioactive gas that can accumulate indoors and increase lung-cancer risk. Nearby facility records and regional maps cannot determine a home’s radon level. Testing is the way to find out.
How it could actually reach a home
Building-specific entry routes and ventilation affect indoor concentrations. A regional designation cannot rule out elevated indoor radon.
What a map cannot tell you
- The home’s measured radon level
- Whether an existing mitigation system functions correctly
What to check next, and who can answer
- Seller / inspector: Request dated radon test results and any mitigation-system records.
- Qualified radon professional: Arrange appropriate testing and discuss mitigation if results warrant it.