Caustic scrubber control device means any add-on device that mixes an aqueous stream or slurry containing a caustic substance with the exhaust gases from an HCl process vent, HCl storage tank, or HCl transfer operation to control emissions of HCl and/or Cl₂.

Chlor-alkali facility means a facility where chlorine and sodium or potassium hydroxide are produced as co-products and hydrogen is produced as a by-product in an electrolytic process using either mercury cells, diaphragm cells, or membrane cells.

Continuous monitoring system, for purposes of the final rule, means liquid flow monitoring devices that meet the performance specifications given in § 63.9025(a); or pH monitoring devices that meet the performance specifications given in § 63.9025(a); or other control devices as mentioned in 63.9025(a) and (b) or § 63.9025(a) and (c).

Control device means an add-on device used to reduce HCl and/or Cl₂ emissions from an HCl process vent, HCl storage tank, or HCl transfer operation at an HCl production facility. An HCl production unit is not a control device.

Deviation means any instance in which an affected source subject to this subpart, or an owner or operator of such a source:

Emission limitation means any emission limit or operating limit.

Emission stream means a gaseous stream from an HCl process vent, an HCl storage tank, an HCl transfer operation, leaking equipment in HCl service, or HCl wastewater operations that is discharged to the atmosphere. Gaseous streams from HCl process vents, HCl storage tanks, and HCl transfer operations that are routed to another process or recycled for reaction or other use (i.e., for pH control) of the HCl and/or Cl₂ are not emission streams. Gaseous streams from HCl transfer operations that are vapor balanced to an HCl storage tank subject to this subpart are not emission streams.

Equipment in HCl service means each pump, compressor, agitator, pressure relief device, sampling connection system, open-ended valve or line, valve, connector, and instrumentation system in an HCl production facility that contains 30 weight percent or greater of liquid HCl or 5 weight percent or greater of gaseous HCl at any time.

HCl process vent means the point of discharge to the atmosphere, or point of entry into a control device, of a gaseous stream that originates from an HCl production unit. The following points of discharge are not HCl process vents:

HCl production facility is defined in § 63.8985(a)(1).

HCl production unit means an absorber or other vessel in which a liquid HCl product is manufactured by absorbing gaseous HCl into either water or an aqueous HCl solution.

HCl storage tank means a tank or other vessel that is used to store liquid HCl product. Tanks or vessels permanently attached to motor vehicles (such as trucks, railcars, barges, or ships) are not HCl storage tanks.

HCl transfer operation means the loading, into a tank truck, railcar, ship, or barge, of liquid HCl from a transfer (or loading) rack (as defined in this section) for which the predominant use is liquid HCl. The predominant use of a transfer (or loading) rack is the material that is loaded by the transfer (or loading) rack in the greatest amount.

HCl wastewater operation means an operation that handles and processes water containing HCl that is discarded from an HCl production facility.

Plant site means all contiguous or adjoining property that is under common control, including properties that are separated only by a road or other public right-of-way. Common control includes properties that are owned, leased, or operated by the same entity, parent entity, subsidiary, or any combination thereof.

Research and development facility means laboratory and pilot plant operations whose primary purpose is to conduct research and development into new processes and products, where the operations are under close supervision of technically trained personnel, and the operations are not engaged in the manufacture of products for commercial sale, except in a de minimis manner.

Responsible official means responsible official as defined in 40 CFR 70.2 of this chapter.

Transfer (or loading) rack means the collection of loading arms and loading hoses, at a single loading rack, that are used to fill tank trucks, railcars, ships, and/or barges. Transfer rack includes the associated pumps, meters, shutoff valves, relief valves, and other piping and valves.

Vapor balanced means connected to a piping system that is designed to collect vapors displaced from tank trucks, rail cars, ships, or barges during loading, and to route the collected vapors to the storage vessel from which the liquid being loaded originated, or to another storage vessel connected by a common header.

Vent means the point of discharge to the atmosphere or to a control device from either an HCl process vent, an HCl storage tank, or an HCl transfer operation.

Water scrubber control device means any add-on device that mixes an aqueous stream not containing a caustic substance with the exhaust gases from an HCl process vent, HCl storage tank, or HCl transfer operation to control emissions of HCl and/or Cl₂.