The Part 264/265, Subpart AA, process vent standards apply to permitted or interim status units, recycling units located at permitted or interim status hazardous waste management facilities, and large quantity generator units (§264/265.1030(b)). Although most recycling units are exempt from regulation under RCRA, §261.6(d) subjects certain recycling units to the Subpart AA standards. Any unit exempt from the facility standards under §264/265.1 is not subject to the process vent standards of Subpart AA.
Once the owner and operator have determined that a facility is subject to Subpart AA, they must consider additional applicability criteria to determine whether the facility is subject to the air emision control requirements. Subpart AA applies to process vents associated with six specific types of units: steam strippers, distillation units, fractionation units, thin-film evaporation units, solvent extraction units, and air strippers. For purposes of the RCRA air regulations, a process vent is any open-ended pipe or stack that is vented to the atmosphere either directly, through a vacuum-producing system, or indirectly, through a tank associated with one of the six specific types of units (§264.1031). Owners and operators at affected facilities that have process vents associated with one of these types of units will be required to meet the standards of Subpart AA if they manage wastes with an organic concentration of at least ten parts per million by weight (ppmw)(§264/265.1030(b)).
Additional guidance on Subpart AA standards is available in the following documents:
Memo, Springer to Regions; March 17, 2004 (RO 14703)
Monthly Call Center Report Questions; June 2000 (RO 14461) (PDF, 10K)
Monthly Call Center Report Questions; March 2000 (RO 14443)
Monthly Call Center Report Questions; February 1996 (RO 13777)
Memo, Michael to Massimino; December 3, 1991 (RO 13517)