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Summary of Central Puget Sound Area Carbon Monoxide (CO) Attainment and Maintenance Plans


The Central Puget Sound Area was designated nonattainment for carbon monoxide (CO) and classified as moderate upon enactment of the Clean Air Act Amendments in 1990.

Washington submitted a CO maintenance plan on February 29, 1996, and EPA announced its proposed approval of the plan on June 11, 1996 (61 FR 29515 (PDF))(4 pp, 127 K, About PDF).

On October 11, 1996, EPA approved the Central Puget Sound Area CO maintenance plan (61 FR 53323 (PDF))(6 pp, 140 K).


The plan relies on control strategies needed to assure attainment of the National Ambient Air Quality Standards (NAAQS) for CO. The strategy relies on the existence of an approved vehicle Inspection and Maintenance program.


  • 40 CFR Part 86, Federal Motor Vehicle Emission Control Program
  • WAC 173-422, Motor Vehicle Emission Inspection

Contingency Measures

  • WAC 173-492, Motor Fuel Specifications for Oxygenated Gasoline
  • PSCAA Regulation II, Section 2.09, Oxygenated Gasoline Contingency Measure & Fee Schedule

EPA Effective Date

October 11, 1996