---
kind: "section"
citation: "40 C.F.R. § 62.14412"
title: "40"
number: "62.14412"
heading: "What stack opacity and visible emissions requirements apply?"
url: "https://uscodex.org/cfr/40/62.14412"
---

# §62.14412. What stack opacity and visible emissions requirements apply?

- (a) Your HMIWI (regardless of size category) must not discharge into the atmosphere from the stack any gases that exhibit greater than 6 percent opacity (6-minute block average).
- (b) Your HMIWI as defined in [§ 62.14400(a)(2)(ii)](/cfr/40/62.14400.md?p=a-2-ii) and utilizing a large HMIWI must not discharge into the atmosphere visible emissions of combustion ash from an ash conveying system (including conveyor transfer points) in excess of 5 percent of the observation period (i.e., 9 minutes per 3-hour period), as determined by EPA Reference Method 22 of [40 CFR part 60](/cfr/40/part60.md), appendix A-7, except as provided in paragraphs [(b)(1)](#b-1) and [(2)](#b-2) of this section.
  - (1) The emissions limit specified in [paragraph (b)](#b) of this section does not cover visible emissions discharged inside buildings or enclosures of ash conveying systems; however, the emissions limit does cover visible emissions discharged to the atmosphere from buildings or enclosures of ash conveying systems.
  - (2) The provisions specified in [paragraph (b)](#b) of this section do not apply during maintenance and repair of ash conveying systems. Maintenance and/or repair must not exceed 10 operating days per calendar quarter unless you obtain written approval from the state agency establishing a date when all necessary maintenance and repairs of ash conveying systems are to be completed.

## Notes

### Amendments

[78 FR 28067, May 13, 2013]

### Source

Source: 65 FR 49881, Aug. 15, 2000, unless otherwise noted.

### Authority

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

### Source

Source: 43 FR 51393, Nov. 3, 1978, unless otherwise noted.

### Amendments

[78 FR 28067, May 13, 2013]