---
kind: "unit"
title: "40"
title_heading: "Protection of Environment"
key: "chI/subchC/part81"
level: "part"
label: "Part 81"
heading: "Designation of Areas for Air Quality Planning Purposes"
release: "ecfr-current"
date: "2026-08-27"
url: "https://uscodex.org/cfr/40/chI-subchC-part81"
sections_count: 344
---

# Part 81 — Designation of Areas for Air Quality Planning Purposes

Title 40 C.F.R. — Protection of Environment › Chapter I — Environmental Protection Agency › Subchapter C — Air Programs

## Contents

- [Subpart A — Meaning of Terms](/cfr/40/chI-subchC-part81-subpartA.md)
- [Subpart B — Designation of Air Quality Control Regions](/cfr/40/chI-subchC-part81-subpartB.md)
- [Subpart C — Section 107 Attainment Status Designations](/cfr/40/chI-subchC-part81-subpartC.md)
- [Subpart D — Identification of Mandatory Class I Federal Areas Where Visibility Is an Important Value](/cfr/40/chI-subchC-part81-subpartD.md)
- [Subpart E — Identification of Interstate Transport Regions](/cfr/40/chI-subchC-part81-subpartE.md)