Section 110 of the Clean Air Act, 42 U.S.C. §7410, requires state and local air pollution control agencies to adopt federally approved control strategies to minimize air pollution. The resulting body of regulations is known as a State Implementation Plan (SIP).

SIPs generally establish limits or work practice standards to minimize emissions of the criteria air pollutants or their precursors. The criteria air pollutants are those for which EPA has established national ambient air quality standards to protect public health: sulfur dioxide, particulate matter, nitrogen oxides, lead (Pb), carbon monoxide, and ozone.

SIPs also include special control strategies for Nonattainment Areas -- areas that are not meeting the standards. These control strategies often include items such as vehicle inspection and maintenance and other reasonably available control technologies (RACT). Finally, SIPs include pre-construction permit requirements for projects that may result in emission increases. These plans have evolved over time and undergo revisions periodically as needed to address local needs or meet updated state or federal requirements. All revisions to the plan must undergo public review and comment prior to adoption and submittal to EPA for approval.