Treat the number as a decision input—not a diagnosis.

Action guidance

4 pCi/L is an action level, not a safety threshold.

Choose the next step

Purpose, device and test length shape the decision.

EPA’s current real-estate guide provides several short-term options: two passive tests at the same time, two sequential passive tests, or an active continuous monitor for at least 48 hours. Outside a transaction, follow the current guidance for the device and situation. A long-term test can provide a better estimate of the year-round average when time allows.

Do not average unrelated tests casually or move a device between locations and treat the values as one result. If conditions were not maintained, discuss whether the measurement should be repeated.

Health context

A building result cannot calculate your personal risk.

EPA identifies radon as a lung-cancer cause and says smoking and radon have a synergistic effect. Its population estimates are not a diagnosis for any person. Exposure history, smoking history and health questions should be discussed with a qualified healthcare professional, not inferred from one building measurement.

Retesting

Measure after mitigation or a major building change.

EPA recommends testing after mitigation to confirm that elevated levels were reduced. It also advises retesting after major renovation and when occupancy moves to a lower level. A system indicator is useful, but it shows system operation—not the indoor radon concentration.