Quick answer
EPA recommends fixing a home when the radon level is 4 pCi/L or higher and considering action between 2 and 4 pCi/L because no level is known to be completely risk-free. Follow test instructions carefully, confirm elevated short-term results as recommended and use a qualified mitigation professional when action is needed.
Why every home can benefit from testing
Radon can enter through cracks, joints, service openings, crawlspaces and other pathways from soil. New and old homes, tight and drafty homes, and homes with or without basements can have elevated levels.
A county radon map describes broad potential, not the result for an individual building. Neighboring homes can test differently, so a low result next door does not replace testing your own home.
Choose the right test for the decision
Short-term tests provide a faster snapshot and are commonly used for screening or real-estate timing. Long-term tests better reflect seasonal variation because radon levels can change with weather, ventilation and building operation.
Use a device and laboratory accepted by the relevant state program, and place it according to instructions in the lowest level that is or could be regularly occupied. Avoid moving or interfering with the device.
Interpret the result carefully
EPA’s action level is 4 picocuries per liter. EPA also recommends considering mitigation for levels between 2 and 4 pCi/L. Follow the recommended confirmation process for the type of test and transaction.
A single measurement is not a medical diagnosis, and the action level is not a boundary between safe and unsafe. The purpose of testing is to make a practical decision about reducing long-term exposure.
How mitigation systems generally work
Common systems use soil suction to draw radon from beneath a slab or crawlspace and vent it above the roof, where it disperses. Sealing openings can support the system but is generally not the only control method.
Ask for a written scope, fan and alarm details, electrical work, discharge location, warranty, post-mitigation test and future maintenance instructions. Requirements and credential programs vary by state.
When to retest
Retest after mitigation to confirm performance, after major foundation or HVAC changes, and periodically according to EPA and state guidance. A system monitor indicates operation, but it does not replace radon measurement.
Keep the test report, mitigation design, warranty and follow-up results with the property records. These documents can be useful for future maintenance and sale disclosures.
Radon Testing Guide for Homeowners checklist
- Use an approved device or laboratory
- Follow closed-house and placement instructions
- Record dates, location and building conditions
- Confirm elevated results as recommended
- Hire qualified mitigation help when needed
- Retest after mitigation and major changes
Frequently asked questions
Can I smell or see radon?
No. Radon is colorless and odorless, so a test is needed.
Are new homes automatically radon-safe?
No. Radon-resistant features can reduce risk, but EPA still recommends testing after occupancy.
Does opening windows fix radon?
Ventilation may temporarily change readings, but it is not a reliable permanent mitigation plan for an elevated result.
Research transparency
How this guide was prepared
This guide summarizes publicly available U.S. government, regulator or industry-source material listed below. It explains planning concepts and questions to verify; it does not provide a property-specific quote, inspection, coverage decision, legal opinion or tax advice.
Sources and references
- EPA radon action level — U.S. Environmental Protection Agency
- How often to test or retest — U.S. Environmental Protection Agency
- EPA map of radon zones — U.S. Environmental Protection Agency
Sources were checked for this guide on July 27, 2026. Policy terms, tax rules, insurance forms, incentives and local requirements can change.
General-information disclaimer
This guide is for general planning only. It is not a quote, policy interpretation, legal advice, tax advice, engineering advice or a substitute for a licensed professional who can review your property and documents.
