---
kind: "section"
citation: "40 C.F.R. § 63.1975"
title: "40"
number: "63.1975"
heading: "How do I calculate the 3-hour block average used to demonstrate compliance?"
url: "https://uscodex.org/cfr/40/63.1975"
---

# §63.1975. How do I calculate the 3-hour block average used to demonstrate compliance?


Before September 28, 2021, averages are calculated in the same way as they are calculated in [§ 60.758(b)(2)(i)](/cfr/40/60.758.md?p=b-2-i) of this subchapter for average combustion temperature and [§ 60.758(c)](/cfr/40/60.758.md?p=c) for 3-hour average combustion temperature for enclosed combustors, except that the data collected during the events listed in [paragraphs (a) through (d)](#a..d) of this section are not to be included in any average computed under this subpart. Beginning no later than September 27, 2021, averages are calculated according to [§ 63.1983(b)(2)(i)](/cfr/40/63.1983.md?p=b-2-i) for average combustion temperature and [§ 63.1983(c)(1)(i)](/cfr/40/63.1983.md?p=c-1-i) for 3-hour average combustion temperature for enclosed combustors, except that the data collected during the event listed in [paragraph (a)](#a) of this section are not to be included in any average computed under this subpart.

- (a) Monitoring system breakdowns, repairs, calibration checks, and zero (low-level) and high-level adjustments.
- (b) **Startups.**
- (c) **Shutdowns.**
- (d) **Malfunctions.**

## Notes

### Amendments

[85 FR 17261, Mar. 26, 2020, as amended at 87 FR 8204, Feb. 14, 2022]

### Source

Source: 85 FR 17261, Mar. 26, 2020, unless otherwise noted.

### Authority

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

### Source

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

### Amendments

[85 FR 17261, Mar. 26, 2020, as amended at 87 FR 8204, Feb. 14, 2022]