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 and 60 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 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.