1998 Revisions to the Carbon Monoxide Maintenance Plan Categories Topics Air Quality Plans Programs California State Implementation Plans Type Information On October 22, 1998, CARB revised the SIP to incorporate the effects of the recent CARB action to remove the wintertime oxygen requirement for gasoline in certain areas.CARB DocumentsNotice of Public Hearing1998 Plan Related Resources 2025 Updates to Motor Vehicle Emissions Budgets for California Ozone State Implementation Plans 2024 Transport State Implementation Plan Amendment 2023 Carbon Monoxide SIP Revision