### Question
Can you define what existing source means?


### Answer
**Existing source** is defined as the following in *42 U.S.C. § 7412*:

> any stationary source other than a new source

#### Citation:
  - *42 U.S.C. § 7412*
  - Heading: **SUBCHAPTER I-PROGRAMS AND ACTIVITIES > Subchapter Referred to in Other Sections > Amendments**

