Use 4.0 pCi/L as a decision switch: at or above → plan mitigation. Between 2 and 4 → seriously consider it. Below 2 → maintain with periodic retesting.1
What the action level is
A national recommendation for when the cost and effort of mitigation are strongly justified by risk reduction. States and Tribes may amplify messaging; they do not rewrite physics.
What it is not
- A guarantee of safety below 4.0
- A building-code maximum for all situations
- A substitute for professional judgment on real estate negotiations
Related reading
What is a safe radon level? · Radon and lung cancer
Sources
- U.S. EPA. Citizen’s Guide to Radon.
Need a local next step? Call (605) 600-6282 to talk through testing, real estate timing, or mitigation for your Rapid City–area home.