Operating day
Operating day refers to the 24-hour period defined by the owner or operator in the Notification of Compliance Status required by 63.1439(5). That 24-hour period may be from midnight to midnight or another 24-hour period. The operating day is the 24-hour period for which daily average monitoring values are determined.
Source
40 CFR § 63.1423
Scoping language
The following terms used in this subpart shall have the meaning given them in subparts A ( 63.2), F ( 63.101), G ( 63.111), and H ( 63.161) as specified after each term: