# 40 C.F.R. § 52.321 (2026): Classification of regions

> Federal · Regulations · In force

URL: https://www.frixlaw.com/law-library/statutes/CFR_T40_P52_S52_321

## Section

- **Citation:** 40 C.F.R. § 52.321 (2026)
- **Heading:** Classification of regions
- **Jurisdiction:** Federal
- **Kind:** Regulations
- **Status:** In force
- **Text as of:** August 14, 2026
- **Source:** Compiled text
- **Location:** Title 40 CFR: Protection of Environment / Chapter I / Part 52 / Subpart G / § 52.321: § 52.321   Classification of regions.

## Text

The revised Denver Emergency Episode Plan, adopted by the State of Colorado February 28, 1996, was submitted by the Governor of Colorado with a September 16, 1997 letter. Air quality control region Pollutant Particulate matter Sulfur oxides Nitrogen dioxide Carbon monoxide Ozone Pawnee Intrastate I III III III III Metropolitan Denver Intrastate I III III I I Comanche Intrastate III III III III III San Isabel Intrastate I III III III III San Luis Intrastate III III III III III Four Corners Interstate IA IA III III III Grand Mesa Intrastate III III III III III Yampa Intrastate III III III III III [37 FR 10855, May 31, 1972, as amended at 39 FR 16346, May 8, 1974; 44 FR 57409, Oct. 5, 1979; 74 FR 47891, Sept. 18, 2009]

## Nearby sections

- [40 C.F.R. § 52.319 (2026) § 52.319   Conditional approval.](https://www.frixlaw.com/law-library/statutes/CFR_T40_P52_S52_319.md)
- [40 C.F.R. § 52.320 (2026) § 52.320   Identification of plan.](https://www.frixlaw.com/law-library/statutes/CFR_T40_P52_S52_320.md)
- [40 C.F.R. § 52.321 (2026) § 52.321   Classification of regions.](https://www.frixlaw.com/law-library/statutes/CFR_T40_P52_S52_321.md)
- [40 C.F.R. § 52.322 (2026) § 52.322   Extensions.](https://www.frixlaw.com/law-library/statutes/CFR_T40_P52_S52_322.md)
- [40 C.F.R. § 52.323 (2026) § 52.323   Approval status.](https://www.frixlaw.com/law-library/statutes/CFR_T40_P52_S52_323.md)
- [40 C.F.R. § 52.324 (2026) § 52.324   Legal authority.](https://www.frixlaw.com/law-library/statutes/CFR_T40_P52_S52_324.md)
- [40 C.F.R. § 52.326 (2026) § 52.326   Area-wide nitrogen oxides (NO X ) exemptions.](https://www.frixlaw.com/law-library/statutes/CFR_T40_P52_S52_326.md)
- [40 C.F.R. § 52.329 (2026) § 52.329   Rules and regulations.](https://www.frixlaw.com/law-library/statutes/CFR_T40_P52_S52_329.md)
- [40 C.F.R. § 52.330 (2026) § 52.330   Control strategy: Total suspended particulates.](https://www.frixlaw.com/law-library/statutes/CFR_T40_P52_S52_330.md)
- [40 C.F.R. § 52.331 (2026) § 52.331   Committal SIP for the Colorado Group II PM 10 . areas.](https://www.frixlaw.com/law-library/statutes/CFR_T40_P52_S52_331.md)
- [40 C.F.R. § 52.332 (2026) § 52.332   Control strategy: Particulate matter.](https://www.frixlaw.com/law-library/statutes/CFR_T40_P52_S52_332.md)
- [40 C.F.R. § 52.343 (2026) § 52.343   Significant deterioration of air quality.](https://www.frixlaw.com/law-library/statutes/CFR_T40_P52_S52_343.md)
- [40 C.F.R. § 52.344 (2026) § 52.344   Visibility protection.](https://www.frixlaw.com/law-library/statutes/CFR_T40_P52_S52_344.md)
- [40 C.F.R. § 52.345 (2026) § 52.345   Stack height regulations.](https://www.frixlaw.com/law-library/statutes/CFR_T40_P52_S52_345.md)

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Source: Frix Law Library, https://www.frixlaw.com/law-library/statutes/CFR_T40_P52_S52_321. Check the current official text before relying on it. Not legal advice.