The South Dakota Department of Environment & Natural Resources recommends hiring a Certified Radon Tester who has completed a radon measurement certification course approved by NRPP.
Visit www.nachi.org/southdakota for details (scroll down the page).
InterNACHI’s free, online “Advanced Radon Measurement Service Provider Course” is approved by NRPP and AARST for both Entry Level (INACH-1) and Continuing Education (INACH-401), and located is at http://www.nachi.org/radon-measurement-service-provider-online-course.htm