This document provides guidance for the EPA Regional Offices to select and modify the ozone monitoring seasons designated for each State in the Code of Federal Regulations (40 CFR 58, Appendix D). Modifications to the original ozone monitoring seasons have been made periodically as new data and information became available; each of these changes has been incorporated into existing ambient air monitoring regulations. These seasons are important because they play a significant role in the estimation of annual ozone NAAQS exceedances and provide the basis for calculations in the Aerometric Information Retrieval System (AIRS) summary files. The monitoring seasons may also be tied to certain State emission regulations. With the 1997 revisions to the National Ambient Air Quality Standards (NAAQS) for ozone (i.e., the addition of a maximum 8-hour average ozone concentration of 0.08 ppm), it has become necessary to redefine the ozone monitoring season for purposes demonstrating attainment. The principal motivation is to develop an understanding of the characteristics of the ozone monitoring season based on the new standard. Another motivation for this guideline document is that reductions in required monitoring can result in considerable cost savings.

"Performed by U.S. Environmental Protection Agency, Office of Air Quality Planning and Standards, Emissions, Monitoring, and Analysis Division"--Colophon. "June 1998." "EPA-454/R-98-001." Includes bibliographical references (p. 18).