---
kind: "section"
citation: "40 C.F.R. § 52.01"
title: "40"
number: "52.01"
heading: "Definitions."
url: "https://uscodex.org/cfr/40/52.01"
---

# §52.01. Definitions.


All terms used in this part but not defined herein shall have the meaning given them in the Clean Air Act and in parts [51](/cfr/40/part51.md) and [60](/cfr/40/part60.md) of this chapter.

- (a) The term stationary source means any building, structure, facility, or installation which emits or may emit an air pollutant for which a national standard is in effect.
- (b) The term commenced means that an owner or operator has undertaken a continuous program of construction or modification.
- (c) The term construction means fabrication, erection, or installation.
- (d) The phrases modification or modified source mean any physical change in, or change in the method of operation of, a stationary source which increases the emission rate of any pollutant for which a national standard has been promulgated under [part 50](/cfr/40/part50.md) of this chapter or which results in the emission of any such pollutant not previously emitted, except that:
  - (1) Routine maintenance, repair, and replacement shall not be considered a physical change, and
  - (2) The following shall not be considered a change in the method of operation:
    - (i) An increase in the production rate, if such increase does not exceed the operating design capacity of the source;
    - (ii) An increase in the hours of operation;
    - (iii) Use of an alternative fuel or raw material, if prior to the effective date of a paragraph in this part which imposes conditions on or limits modifications, the source is designed to accommodate such alternative use.
- (e) The term startup means the setting in operation of a source for any purpose.
- (f) [Reserved]
- (g) The term heat input means the total gross calorific value (where gross calorific value is measured by ASTM Method D2015-66, D240-64, or D1826-64) of all fuels burned.
- (h) The term total rated capacity means the sum of the rated capacities of all fuel-burning equipment connected to a common stack. The rated capacity shall be the maximum guaranteed by the equipment manufacturer or the maximum normally achieved during use, whichever is greater.

## Notes

### Amendments

[37 FR 19807, Sept. 22, 1972, as amended at 38 FR 12698, May 14, 1973; 39 FR 42514, Dec. 5, 1974; 43 FR 26410, June 19, 1978]

### Source

Source: 37 FR 10846, May 31, 1972, unless otherwise noted.

### Authority

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

### Amendments

[40 FR 5521, Feb. 6, 1975]

### Amendments

[37 FR 19807, Sept. 22, 1972, as amended at 38 FR 12698, May 14, 1973; 39 FR 42514, Dec. 5, 1974; 43 FR 26410, June 19, 1978]