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Indiana Department of Environmental Management

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Air Quality

The air quality portion of the IDEM Permit Guide is intended to serve as a reference for common terminology relating to air quality programs and basic approval and permitting requirements. It is aimed at helping business owners and operators and members of the general public gain a better understanding of the air permitting programs that help protect Hoosiers and the air we breathe.

In addition to overseeing the construction and operation of sources of air emissions, IDEM’s Office of Air Quality oversees approval programs for asbestos and open burning. Air Quality topics are presented in three sections: Air permitting, Asbestos information, and Open burning.

The United States Congress passed the first Clean Air Act in 1963, providing a Nationwide Air Quality Management System. Congress passed major amendments to the Clean Air Act in 1970, 1977 and 1990. The Clean Air Act established a system to measure air quality and provide for continuous improvement. It is implemented by the United States Environmental Protection Agency (U.S. EPA). Indiana’s air permitting program is approved by U.S. EPA.

Persons or businesses planning to construct a new facility, expand a facility, operate a facility or carry out an activity that will emit one or more regulated pollutants into the air will need to consult with IDEM’s Office of Air Quality about state and federal permitting and approval requirements. Permits regulate the amount of air pollution that can be released by a source. The greater the expected emissions at a new or modified source, the higher the level of permit approval required. A source’s Potential to Emit (PTE) a regulated pollutant (or more than one regulated pollutant) is a primary factor in determining the appropriate approval or permit required for its construction and operation.

The air permit process requires sources to send applications to IDEM describing the equipment they have or, for expansions, equipment they want to add. IDEM uses uncontrolled potential to emit (PTE), the maximum potential air pollution from the equipment if it is operated 24 hours every day with no air pollution controls, to determine the level of air permit the source will need. IDEM uses controlled, or limited PTE to determine which state and federal rules apply to the emission units at each facility. In some cases, air pollution control techniques or add-on control equipment may be required for demonstrating compliance with applicable state or federal rules. IDEM drafts the appropriate type of permit that contains all applicable state and federal requirements for controlling emissions. IDEM seeks public comment on draft permits for air permit approvals for initial air permits and for revisions or modifications that will result in significant changes to a permitted source or significant changes to the operating requirements for a permitted source. Certain types of permits also require review by the US EPA prior to issuance.

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