Ambient monitoring's role in PSD increments is primarily for which regulatory action?

• A. Permit determinations
• B. Compliance training
• C. Emergency response
• D. Permit determinations

Answer: (D)

PSD increments are thresholds that set how much ambient pollutant concentration can increase in an attainment area. Ambient monitoring provides the actual air quality data needed to see how a proposed project would affect those thresholds. When a new major source or modification is considered, regulators use monitoring data together with emission estimates to determine whether the project would consume part of the remaining increment or push concentrations toward the limit. That information is what drives the permit decision—whether to issue the permit, and under what controls or conditions. So the role of ambient monitoring in PSD increments is best described as informing permit determinations.

While monitoring data can be used later to verify compliance or guide emergency planning, the primary use in this context is to support the permit review and approval process.