Okla. Admin. Code § 252:100-42-2
The following words and terms when used in this Subchapter shall have the following meanings unless the context clearly indicates otherwise.
"Area of concern" or "AOC" means a geographic area in Oklahoma designated as having exceeded a TAC maximum acceptable ambient concentration (MAAC).
"Emissions unit" means, for the purposes of this Subchapter, any part of a stationary source which emits a TAC.
"Malfunction" means any sudden, infrequent, and not reasonably preventable failure of air pollution control equipment, process equipment, or a process to operate in a normal or usual manner. Failures that are caused in part by poor maintenance or careless operation are not malfunctions.
"Maximum acceptable ambient concentration" or "MAAC" means the action levels and averaging times contained in Appendix O of this Chapter for TAC.
"Toxic air contaminant" or "TAC" means any substance listed in Appendix O of this Chapter.
Okla. Admin. Code § 252:100-42-2