Enforcement is a critical component of regulatory air quality programs that helps ensure a level playing field across all companies in an industrial sector. Appropriate methods of enforcement ensure compliance with regulations which helps improve human health and the environment by ensuring that required reductions in air pollution actually occur. When violations are identified, regulators have several options: mandated requirements to install air pollution control devices or process modifications; civil penalties (e.g., fines); requirements to support air pollution research and control measures; and, in criminal cases, imprisonment. The appropriate types of enforcement can vary considerably from location to location, depending upon many local factors (e.g., local air quality, local enforcement policies).