40 CFR § 52.1371 - Classification of regions.

---
identifier: "/us/cfr/t40/s52.1371"
source: "ecfr"
legal_status: "authoritative_unofficial"
title: "40 CFR § 52.1371 - Classification of regions."
title_number: 40
title_name: "Protection of Environment"
section_number: "52.1371"
section_name: "Classification of regions."
chapter_name: "ENVIRONMENTAL PROTECTION AGENCY"
subchapter_number: "C"
subchapter_name: "AIR PROGRAMS"
part_number: "52"
part_name: "APPROVAL AND PROMULGATION OF IMPLEMENTATION PLANS"
positive_law: false
currency: "2026-04-05"
last_updated: "2026-04-05"
format_version: "1.1.0"
generator: "[email protected]"
authority: "42 U.S.C. 7401"
cfr_part: "52"
---


# 52.1371 Classification of regions.

The Montana Emergency Episode Avoidance Plan was revised with an August 2, 2004 submittal by the Governor. The August 2, 2004 Emergency Episode Avoidance Plan classified the Air Quality Control Regions (AQCR) as follows:

|  |  |  |  |  |  |
| --- | --- | --- | --- | --- | --- |
| Billings Intrastate AQCR 140 | III | III | III | III | III |
| Great Falls Intrastate AQCR 141 | III | III | III | III | III |
| Helena Intrastate AQCR 142 | III | III | III | III | III |
| Miles City Intrastate AQCR 143 | III | III | III | III | III |
| Missoula Intrastate AQCR 144 | III | III | III | III | III |

[64 FR 68038, Dec. 6, 1999, as amended at 66 FR 31550, June 12, 2001; 71 FR 21, Jan. 3, 2006]