The series relates to the monitoring of air and water quality and, specifically, the quality assurance and quality control of monitoring instruments and the data generated. The records include correspondence, comments about proposals, action requests, background information, details about proposed installations, copies of letters of permission to conduct studies, drafts of approvals for facilities. The records may also include maintenance information, calibration reports, audit reports, monthly control charts, monthly reports, information on sampling methods/procedures or changes in analysis procedures in conducting tests for specific substances.