Areas Participating in the Oxygenated Gasoline Program
July 1, 1999
Introduction
Carbon monoxide (CO) is a colorless, odorless, and poisonous gas produced by incomplete burning of fuels used in internal combustion engines. Elevated levels of CO generally occur during the winter months because of increased CO emissions from cold vehicles and the occurrence of temperature inversions, which trap pollutants near the ground and inhibit dispersion and dilution. The U.S. Environmental Protection Agency (EPA) has set National Air Ambient Quality Standards (NAAQS) for CO that specify upper limits of 35 ppm for a 1-hour period and 9 ppm for an 8-hour period. Generally, the 8-hour limit is the more restrictive and virtually all exceedances in recent years involve violation of this limit. Monitoring stations are allowed one exceedance of the air quality standard per year. A second exceedance consititutes a violation.
An important program for reducing ambient CO concentrations is the use of cleaner burning oxygenated gasoline. Extra oxygen enhances fuel combustion and helps to offset fuel-rich operating conditions, particularly during vehicle starting in cold weather. Section 211(m) of the Clean Air Act (42 U.S.C. 7401-7671q) requires that gasoline containing at least 2.7 percent oxygen by weight is to be used in the wintertime in those areas of the county that exceed the CO NAAQS. The winter oxygenated gasoline program applies to all gasoline sold in the larger of the Consolidated Metropolitan Statistical Area (CMSA) or Metropolitan Statistical Area (MSA) in which the nonattainment area is located.
For a current list of oxygenated gasoline program areas, refer to the U.S. Environmental Protection Agency, Office of Mobile Sources, State Winter Oxygenated Fuel Programs. For a current list of ozone nonattainment areas, refer to the EPA Green Book.
The control period is that portion of the year in which the area is prone to high ambient concentrations of CO, as determined by the EPA ("Guidelines for Oxygenated Gasoline Credit Programs and Guidelines on Establishment of Control Periods Under Section 211(m) of the Clean Air Act as Amended," 57 FR 47853, October 20, 1992).
Original Oxygenated Gasoline Control Areas
Beginning on November 1, 1992, 39 areas of the county were required to participate in the oxygenated gasoline program. These 39 original CO nonattainment areas had CO design values of 9.5 ppm or above based on data for the 2-year period of 1988 and 1989.