Which regulatory references govern ambient air monitoring in Colorado?

• A. Local city ordinances.
• B. International standards; no state or federal.
• C. Only state regulations; federal standards do not apply.
• D. Clean Air Act, NAAQS, EPA QA/QC guidelines, and state regulations and QA/QC manuals from CDPHE.

Answer: (D)

Ambient air monitoring is governed by multiple layers of rules, combining national standards, federal quality requirements, and state-specific guidance. The Clean Air Act establishes the framework and the National Ambient Air Quality Standards define the pollutant limits that the monitoring network supports. The EPA QA/QC guidelines provide the procedures and quality assurance practices needed to produce reliable, comparable data across sites and over time. Colorado adds its own requirements through CDPHE, including state regulations and QA/QC manuals that lay out how monitors should be operated, how data are validated, and how reporting aligns with federal expectations. This combination ensures both national consistency and state-specific implementation.

Local city ordinances don’t set the statewide ambient monitoring framework, international standards aren’t binding in the U.S., and federal standards alone aren’t sufficient without state regulations and QA/QC practices. The most complete and correct reference set includes the Clean Air Act, NAAQS, EPA QA/QC guidelines, and the state regulations and QA/QC manuals from CDPHE.