---
kind: "section"
citation: "40 C.F.R. § 51.906"
title: "40"
number: "51.906"
heading: "Redesignation to nonattainment following initial designations for the 8-hour NAAQS."
url: "https://uscodex.org/cfr/40/51.906"
---

# §51.906. Redesignation to nonattainment following initial designations for the 8-hour NAAQS.


For any area that is initially designated attainment or unclassifiable for the 8-hour NAAQS and that is subsequently redesignated to nonattainment for the 8-hour ozone NAAQS, any absolute, fixed date applicable in connection with the requirements of this part is extended by a period of time equal to the length of time between the effective date of the initial designation for the 8-hour NAAQS and the effective date of redesignation, except as otherwise provided in this subpart.


## Notes

### Amendments

[70 FR 71700, Nov. 29, 2005]

### Source

Source: 69 FR 23996, Apr. 30, 2004, unless otherwise noted.

### Authority

Authority: 23 U.S.C. 101; 42 U.S.C. 7401-7671q.

### Source

Source: 36 FR 22398, Nov. 25, 1971, unless otherwise noted.

### Amendments

[70 FR 71700, Nov. 29, 2005]