The Colorado Department of Public Health & Environment recommends hiring a Certified Radon Tester who has completed a radon measurement certification course approved by NRPP and AARST.
Visit http://www.nachi.org/colorado-certified-licensed-home-inspector.htm for details.
InterNACHI’s free, online “Advanced Radon Measurement Service Provider Course” is NRPP- and AARST-approved and located is at http://www.nachi.org/radon-measurement-service-provider-online-course.htm