Unless specifically defined in the Texas Clean Air Act (Texas Health and Safety Code, Chapter 382), or in §101.1 or §112.1 of this title (relating to Definitions, respectively), the terms in this division have the meanings commonly used in the field of air pollution control. The following meanings apply in this division unless the context clearly indicates otherwise.     
       (1) Block one-hour average--An hourly average of data, collected starting at the beginning of each clock hour of the day and continuing until the start of the next clock hour of the day (e.g., from 12:00:00 to 12:59:59).      
       (2) Continuous Monitoring--Monitoring for which readings are recorded at least once every 15 minutes.      
       (3) Howard County sulfur dioxide (SO               2              ) nonattainment area--The portion of Howard County designated by the United States Environmental Protection Agency as nonattainment for the 2010 SO               2              National Ambient Air Quality Standard, 40 Code of Federal Regulations §81.344.      
       (4) Off-line--With respect to a carbon black oil furnace, a period when either:                (A) only natural gas and combustion air are supplied to the furnace burners (no oil is supplied to the furnace burners), and the furnace is not manufacturing carbon black or generating tail gas; or                 (B) the oil furnace is not operating.        
       (5) On-line--Not "off-line," as defined in paragraph (4) of this subsection.      
       (6) Production unit--The combined equipment used in the manufacture of carbon black, including but not limited to, carbon black oil furnaces or reactors, bag unit filters, cyclones, fans, and carbon black dryers as specified in this rule. Production Units 1 and 2 consist of nine carbon black oil furnaces that produce tail gas and five carbon black dryers that combust tail gas and exhaust emissions through Dryer Stack Units Nos. 1 & 2 (Emission Point Number (EPN) 7A). Production Unit 3 consists of four carbon black oil furnaces that produce tail gas and two carbon black dryers that combust tail gas and exhaust emissions through Dryer Stack Unit No. 3 (EPN 12A). A portion of the tail gas from all of the furnaces is also combusted in the Incinerator + HRSG (EPN 13A) or by Flare 4 (EPN Flare 4).      
       (7) Tail gas--The exit gaseous stream of a carbon black oil furnace consisting of water vapor, carbon monoxide, hydrogen, pyrolysis by-products, and reduced and organic sulfur compounds as a result of the manufacture of carbon black.      
     Source Note:        The provisions of this §112.111 adopted to be effective October 27, 2022, 47 TexReg 6985