### Question
What does modification mean?


### Answer
**Modification** has the following meaning in *42 U.S.C. § 7411*:

> any physical change in, or change in the method of operation of, a stationary source which increases the amount of any air pollutant emitted by such source or which results in the emission of any air pollutant not previously emitted

#### Citation:
  - *42 U.S.C. § 7411*
  - Heading: **CHAPTER 83-ENERGY EXTENSION SERVICE > SUBCHAPTER I-PROGRAMS AND ACTIVITIES > Part A-Air Quality and Emission Limitations**

