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If a source has a potential to emit (PTE) below registration thresholds, it may be exempt from getting an air permit. Owners and operators of such sources may obtain a Letter of Exemption from IDEM’s Office of Air Quality (OAQ). Having a Letter of Exemption is not required, but it can be beneficial because it provides:

  • Verification that the source is exempt from air permit requirements, as long as the source does not make changes that increase the PTE above exemption thresholds that would trigger air permit requirements.
  • Information about other air pollution regulations and requirements applicable to the source. For example, small sources that are not required to have an air permit may be subject to other state and/or federal air pollution control regulations.

It is a voluntary decision on the part of a facility to apply for a Letter of Exemption.

Assistance is available from IDEM’s Office of Air Quality (OAQ). In addition, IDEM’s Compliance and Technical Assistance Program (CTAP) offers free and confidential compliance assistance to help small businesses understand requirements.

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