Source categories which have been subcategorized for purposes of MACT rule development:

MACT	Subcategories	Basis for subcategorization
Coke Ovens: Pushing, Quenching, and Battery Stacks

Subpart CCCCC

66FR35325	Pushing emissions

- Short by-product batteries w/vertical flues

- Tall by-product batteries w/vertical flues

- All by-product batteries w/horizontal flues

- All non-recovery batteries	Differences in processes and emission characteristics
Cyanide Chemicals Manufacturing

Subpart YY

65FR76407	By type of process

- HCN manufacturing using the BMA/Andrussow process

- HCN manufacturing using the Sohio process

- Sodium cyanide manufacturing using the neutralization process	Differences in processes and emission characteristics; for the other emission sources in the source category (storage tanks, equipment leaks, transfer operations, and wastewater) there was no subcategorization because no difference between the processes could be seen
Ferroalloys

Subpart XXX

64FR27450	By furnace type

- Open submerged arc furnace

- Semi-sealed submerged arc furnace

By product

- Ferromanganese

- Silicomanganese

By power input	Differences in processes and emission characteristics
Flexible Polyurethane Foam Fabrication

Subpart MMMMM

66FR41717	By process type

- Loop slitter adhesive use

- Flame lamination	Differences in process, controls and HAP emissions characteristics; subcategories are rarely or never collocated with each other
Polymers and Resins I and IV

Subpart U

61FR46906

Subpart JJJ

61FR48208	By product produced

By process

- Batch

- Continuous	We established subcategories based upon the product produced by the process and the type processing utilized (i.e., whether the process was a batch or continuous operation). The rationale for this subcategorization was each product used a different combination of HAP feedstock monomers with varying physical/chemical properties, which in conjunction with the type processing, determined emission characteristics. These characteristics in turn affected applicable control technologies, their effectiveness, and costs of control.
POTW

Subpart VVV

64FR57572	By source of influent

- Industrial

- Non-industrial	Differences in processes and emission characteristics
Printing and publishing

Subpart KK

61FR27132	Publication rotogravure printing

Product and packaging rotogravure printing

Wide-web flexographic printing	Differences in inks and coatings; in emission reduction techniques; and in recordkeeping practices
Pulp and Paper

Subpart S

63FR18504	By production process

- Kraft

- Sulfite

- Soda

- Semi-chemical	Differences in processes and emission characteristics
Secondary lead

Subpart X

60FR32587	By furnace type

- Blast furnaces

- Reverberatory furnace

- Blast reverberatory combination	Differences in processes and emission characteristics