What EPA actually recommends about radon
Nearly every radon conversation in a home sale eventually cites the EPA, and the citation is frequently wrong in the same specific way: someone describes a recommendation as a legal requirement.
Here is what the guidance actually says, and what it does not.
The action level and the consideration band
EPA recommends taking action to reduce indoor radon at or above 4 picocuries per litre. Between 2 and 4 pCi/L, it suggests considering action — a softer statement reflecting that risk decreases continuously rather than dropping to zero below a threshold.
There is no level EPA describes as entirely without risk, and the agency notes that radon risk exists at low concentrations too. The 4 pCi/L figure is a practical action point, not a safety boundary.
How EPA says to test
The guidance is consistent and specific: measure on the lowest level you live in or could reasonably finish; keep the building under closed conditions for twelve hours before a short-term test and throughout it; place detectors away from exterior walls, drafts, supply registers, and sump pits; and confirm a short-term result before spending money on a system.
It also treats do-it-yourself testing as legitimate for your own information — a properly used kit from a recognized laboratory is a real measurement. In a transaction, the parties usually want an independent measurement by a credentialed professional, which is a practical convention rather than an EPA requirement.
What it says about after the work
EPA recommends confirming that a mitigation system worked with a post-mitigation measurement, and retesting periodically thereafter — commonly framed as every two years, and again after any significant change to the house or its heating and ventilation.
That retest guidance is the part most homeowners forget, and it is the reason a system with a folder of measurements is worth more than a system with only an invoice.
What EPA guidance is not
It is not a building code, it is not a mandate, and it does not create a legal obligation for a seller to install a system at any concentration. States write their own disclosure rules and their own licensing rules, and in the states this platform serves those rules center on disclosure and credentialing rather than on compulsory remediation.
This matters in negotiation, where one side occasionally asserts that a reading above 4 pCi/L legally requires a repair. It does not. It is a health recommendation worth acting on, and the decision about who pays remains a term of the contract.
EPA recommendations: common questions
Is there a safe level of radon?
EPA does not describe any concentration as entirely without risk, which is why the guidance uses an action level rather than a safety threshold. Risk decreases as concentration decreases, and reducing an elevated level reduces exposure proportionately. The 4 pCi/L figure marks where action is recommended, not where risk begins.
Why does EPA recommend confirming a short-term test?
Because a two-to-seven-day measurement samples a short window of weather, occupancy, and building conditions, and those things move the number. A confirming short-term test or a long-term detector reduces the chance of spending four figures on the basis of an unrepresentative weekend — or of dismissing a genuine problem because one test happened to fall in favorable conditions.
Does EPA say I need a professional to test?
No. EPA treats do-it-yourself testing with a kit from a recognized laboratory as a legitimate way to find out about your own home. Professional measurement becomes important in transactions, where an interested party's self-reported number is easy for the other side to challenge, and in states that require a license for measurement performed for compensation.
Keep reading
- How testing works — Devices, placement, closed-building conditions, and what invalidates a result.
- Is mitigation worth it — Clear yes, clear no, and the genuinely marginal middle.
- Post-mitigation testing — The measurement that proves the system worked — and what if it did not.
- Failed test during inspection — The inspection-window playbook, in the order the clock demands.
- All homeowner guides — every decision page in one place.
Act at 4, consider between 2 and 4, test the lowest lived-in level under closed conditions, confirm before spending, verify afterward, retest every couple of years. That is the whole of the guidance, and none of it is a mandate.
Sources
- U.S. EPA — Radon
- U.S. EPA — A Citizen’s Guide to Radon
- U.S. EPA — Consumer’s Guide to Radon Reduction
Act on your own number, not an average
If your confirmed result is at or above the action level, independent licensed contractors can quote your house directly — free, with no obligation.