---
kind: "unit"
title: "40"
title_heading: "Protection of Environment"
key: "chI/subchC/part51/subpartDD"
level: "subpart"
label: "Subpart DD"
heading: "Requirements for Reclassified Ozone Nonattainment Areas"
release: "ecfr-current"
date: "2026-08-27"
url: "https://uscodex.org/cfr/40/chI-subchC-part51-subpartDD"
sections_count: 4
---

# Subpart DD — Requirements for Reclassified Ozone Nonattainment Areas

Title 40 C.F.R. — Protection of Environment › Chapter I — Environmental Protection Agency › Subchapter C — Air Programs › Part 51 — Requirements for Preparation, Adoption, and Submittal of Implementation Plans

## Sections

- [§51.1400. Definitions.](/cfr/40/51.1400.md)
- [§51.1401. Applicability of part 51.](/cfr/40/51.1401.md)
- [§51.1402. SIP submission and control measure implementation deadlines for reclassified ozone nonattainment areas.](/cfr/40/51.1402.md)
- [§51.1403. Applicability of ozone SIP requirements for former classification after reclassification.](/cfr/40/51.1403.md)