Managing internal quality control procedures are key to the assurance of statistical certainty in radon measurements. Quality control measurements of radon devices must be performed routinely to test measurement accuracy and/or precision. In addition, quality control procedures hold the measurement provider accountable to EPA, NEHA-NRPP and/or state specific regulations. Below are 5 general categories of quality control measurements. Please see Appendix A for examples of precision control charts for further assistance in developing individualized QAPs.