---
kind: "section"
citation: "40 C.F.R. § 63.9991"
title: "40"
number: "63.9991"
heading: "What emission limitations, work practice standards, and operating limits must I meet?"
url: "https://uscodex.org/cfr/40/63.9991"
---

# §63.9991. What emission limitations, work practice standards, and operating limits must I meet?

- (a) You must meet the requirements in paragraphs [(a)(1)](#a-1) and [(2)](#a-2) of this section. You must meet these requirements at all times.
  - (1) You must meet each emission limit and work practice standard in Table 1 through 3 to this subpart that applies to your EGU, for each EGU at your source, except as provided under [§ 63.10009](/cfr/40/63.10009.md).
  - (2) You must meet each operating limit in table 4 to this subpart that applies to your EGU.
- (b) As provided in [§ 63.6(g)](/cfr/40/63.6.md?p=g), the Administrator may approve use of an alternative to the work practice standards in this section.
- (c) You may use the alternate SO2 limit in Tables 1 and 2 to this subpart only if your EGU:
  - (1) Has a system using wet or dry flue gas desulfurization technology and an SO2 continuous emissions monitoring system (CEMS) installed on the EGU; and
  - (2) At all times, you operate the wet or dry flue gas desulfurization technology and the SO2 CEMS installed on the EGU consistent with [§ 63.10000(b)](/cfr/40/63.10000.md?p=b).

## Notes

### Amendments

[77 FR 9464, Feb. 16, 2012, as amended at 77 FR 23402, Apr. 19, 2012; 81 FR 20180, Apr. 6, 2016; 89 FR 38564, May 7, 2024; 91 FR 9114, Feb. 24, 2026]

### Source

Source: 77 FR 9464, Feb. 16, 2012, unless otherwise noted.

### Authority

Authority: 42 U.S.C. 7401 et seq.

### Source

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

### Amendments

[77 FR 9464, Feb. 16, 2012, as amended at 77 FR 23402, Apr. 19, 2012; 81 FR 20180, Apr. 6, 2016; 89 FR 38564, May 7, 2024; 91 FR 9114, Feb. 24, 2026]