Code of Federal Regulations > Title 40 > Chapter I > Part 63 > Subpart DDDD > Appendix - Table 2 to Subpart DDDD of Part 63

Regulations last checked for updates: Feb 20, 2025

Title 40 - Protection of Environment last revised: Nov 20, 2025

Appendix - Table 2 to Subpart DDDD of Part 63—Operating Requirements

If you operate a(n) . . .	You must . . .	Or you must . . .
(1) Thermal oxidizer	Maintain the 3-hour block average firebox temperature above the minimum temperature established during the performance test	Maintain the 3-hour block average THC concentration ¹ in the thermal oxidizer exhaust below the maximum concentration established during the performance test.
(2) Catalytic oxidizer	Maintain the 3-hour block average catalytic oxidizer temperature above the minimum temperature established during the performance test; AND check the activity level of a representative sample of the catalyst annually except as specified in footnote “2” to this table	Maintain the 3-hour block average THC concentration ¹ in the catalytic oxidizer exhaust below the maximum concentration established during the performance test.
(3) Biofilter	Maintain the 24-hour block biofilter bed temperature within the range established according to § 63.2262(m)	Maintain the 24-hour block average THC concentration ¹ in the biofilter exhaust below the maximum concentration established during the performance test.
(4) Control device other than a thermal oxidizer, catalytic oxidizer, or biofilter	Petition the EPA Administrator for site-specific operating parameter(s) to be established during the performance test and maintain the average operating parameter(s) within the range(s) established during the performance test	Maintain the 3-hour block average THC concentration ¹ in the control device exhaust below the maximum concentration established during the performance test.
(5) Process unit that meets a compliance option in Table 1A to this subpart, or a process unit that generates debits in an emissions average without the use of a control device	Maintain on a daily basis the process unit controlling operating parameter(s) within the ranges established during the performance test according to § 63.2262(n)	Maintain the 3-hour block average THC concentration ¹ in the process unit exhaust below the maximum concentration established during the performance test.

¹ You may choose to subtract methane from THC measurements.

² You may forego the annual catalyst activity check during the calendar year when a performance test is conducted according to Table 4 to this subpart.

[85 FR 49460, Aug. 13, 2020]

authority: 42 U.S.C. 7401

source: 57 FR 61992, Dec. 29, 1992, unless otherwise noted.