Those performing radon measurement or radon mitigation in Colorado must be licensed, unless they meet an exemption. Licensure in Colorado requires certification from either the National Radon Proficiency Program or the National Radon Safety Board.
Check to see if your radon professional is licensed in Colorado here.
Find an NRPP Certified Radon Mitigation or Measurement Professional here.
Find a NRSB Certified Radon Professional here.