Plain answer
Subpart AA follows process vents from five specified hazardous-waste treatment operations at 10 parts per million by weight total organics. Subpart BB follows specified equipment contacting hazardous waste at 10 percent by weight total organics. Subpart CC follows tanks, surface impoundments, and containers, generally using a 500 parts per million by weight volatile-organic screen. Each test also depends on facility status, unit type, exclusions, and documentation.
Compare the three tests
| Subpart | What it follows | Concentration screen | Primary question |
|---|---|---|---|
| AA | Process vents from five listed treatment operations | 10 ppmw total organics | Is the listed operation conducted in a covered unit? |
| BB | Pumps, valves, compressors, pressure-relief devices, sampling systems, open-ended lines, flanges, and connectors | 10 percent by weight total organics | Does the equipment contain or contact qualifying hazardous waste? |
| CC | Tanks, surface impoundments, and containers | Generally 500 ppmw average volatile organics at the point of waste origination | Does the unit or waste qualify for an exclusion or alternative treatment exemption? |
The numbers are not interchangeable. Ten ppmw, 10 percent, and 500 ppmw measure different things for different regulatory purposes.
Start with facility and unit status
Before applying a concentration threshold, identify why the unit is within the regulatory universe. For Subparts AA and BB under Part 265, the listed operation or equipment must be associated with one of three categories:
- A unit subject to Part 270 permitting
- A nonexempt unit, including certain recycling units, at a facility otherwise subject to Part 270 permitting
- A 90-day tank or container operating under §262.17 that is not a recycling unit under §261.6
A concentration result alone does not establish applicability. A solvent still can exceed 10 ppmw and still fall outside Subpart AA if neither the operation nor its unit fits the applicability provision.
Subpart AA follows five specified process vents
Subpart AA applies to process vents associated with distillation, fractionation, thin-film evaporation, solvent extraction, and air or steam stripping operations that manage hazardous waste with a time-weighted annual average total organic concentration of at least 10 ppmw.
Documenting a below-threshold conclusion
To show that a vent is outside the substantive standards because the waste is below 10 ppmw, §265.1034(d) allows direct measurement or documented knowledge. For continuously generated waste, the determination is made annually and whenever the waste or generating or treatment process changes.
What applies after the screen
Subpart AA establishes a facility-wide limit. The owner or operator must either keep total emissions from all affected process vents below both 1.4 kilograms per hour and 2.8 megagrams per year, or reduce total organic emissions from all affected vents by 95 percent using a control device. Because affected vents are summed, adding one vent can change the facility-wide result.
Subpart BB follows equipment leaks
Subpart BB applies to specified equipment that contains or contacts hazardous waste with total organic concentrations of at least 10 percent by weight and is associated with one of the covered unit categories. Each covered component must be marked so it can be readily distinguished from other equipment.
The determination may use specified test methods or documented knowledge. Samples must represent the highest total-organic content expected at the equipment. Once equipment has been determined to meet or exceed 10 percent, that conclusion can be revised downward only through direct measurement under the specified procedures.
Two exclusions that require records
| Condition | Effect | Required support |
|---|---|---|
| Vacuum service | Excluded from §§265.1052 through 265.1060 | Identification in the §265.1064(g)(5) log |
| Covered service for less than 300 hours per year | Excluded from §§265.1052 through 265.1060 | Identification in the §265.1064(g)(6) log |
These are record-conditioned exclusions. If the equipment qualifies but the log does not identify it, the compliance file has no documented exclusion to show an inspector.
Subpart CC follows tanks, surface impoundments, and containers
Subpart CC applies to tanks, surface impoundments, and containers subject to Part 265 Subparts J, K, or I. It does not directly apply to miscellaneous units under Subpart X. A permit writer may impose air controls on a miscellaneous unit through the Part 264 Subpart X environmental-performance standards, but that is different from direct Subpart CC applicability.
Use the correct regulatory point
A unit can avoid the control standards under §265.1083(c)(1) when every hazardous waste entering it has an average volatile-organic concentration below 500 ppmw at the point of waste origination. For an onsite generator, that point is where the solid waste is determined to be hazardous waste, not automatically the downstream tank or drum where it is accumulated.
Screen unit-level exclusions early
- Containers with a design capacity of 0.1 cubic meter or less
- Qualifying legacy waste with no additions since December 6, 1996
- Units used solely for specified corrective-action or CERCLA remediation waste
- Units used solely for qualifying radioactive mixed waste
- Units certified as controlled under an applicable Part 60, 61, or 63 requirement
- A tank with a process vent as defined in §264.1031
Section 265.1083(c)(2) also contains treatment-based exemptions. Those routes require the specified performance determination. They are not satisfied merely by stating that the waste was treated.
Large quantity generators can be covered
These standards are not limited to commercial treatment, storage, and disposal facilities. Section 262.17 directs large quantity generators using 90-day containers to the applicable requirements of Part 265 Subparts AA, BB, and CC, and directs large quantity generators using tanks to applicable Subparts AA through CC.
The generator provisions for small and very small quantity generators do not contain the same cross-reference. That does not override another independently applicable treatment, storage, disposal, permitting, or facility status.
Use the right part
Permitted facilities generally use Part 264. Interim-status facilities and qualifying large quantity generator accumulation units generally use Part 265.A control device does not end the analysis
Routing emissions to a closed-vent system and control device can replace a particular component or unit-control route, but it does not erase applicability. It can also create continuous monitoring, performance-demonstration, inspection, repair, and recordkeeping obligations.
Companion field note
Does routing RCRA air emissions to a control device simplify compliance?
The answer differs under Subparts BB and CC, and a control device is not a general alternative for every BB component.
Compare the control-device pathways ↗Keep the three analyses separate
A defensible file allows a reviewer to trace each conclusion from the waste and unit to the applicable standard.
- AA: Identify the listed operation, process vent, covered-unit category, concentration basis, and facility-wide emissions.
- BB: Inventory and mark each component, document the waste concentration and service, and assign the applicable compliance method or recorded exclusion.
- CC: Identify each tank, surface impoundment, and container; establish the point of waste origination; and document the applicable control level, exclusion, or treatment route.
- Keep concentration determinations and exemption rationales separate by subpart.
- Connect field tags, drawings, vent routes, inspections, repair records, and waste data.
- Reevaluate after waste, process, equipment, or unit-status changes.
Need a facility-specific answer?
ACP can connect the standards to the waste streams, equipment, records, and operating conditions at your facility.
Primary references
Confirm requirements against the current regulation, the applicable part for the facility's status, and the authorized state program.
This field note is a general overview. Applicability depends on facility status, unit configuration, waste composition, service conditions, exclusions, and the authorized state program.