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Ozone (1-Hour Standard)


Current Status

Nonattainment Area

Adams, Arapahoe, Boulder, Broomfield, Denver, Douglas, and Jefferson Save & Exit

Attainment Deadline

N/A – standard revoked 2005


A revised ozone standard (0.12 parts per million (ppm) over a one hour period) was promulgated by the Environmental Protection Agency (EPA) in 1978. A violation occurs when an area exceeds the ozone standard more than three times in three years at a given monitor. In March 1978, the EPA designated the Denver Metro Area (DMA) as nonattainment for the Ozone NAAQS.

The EPA revoked the 1-hour standard for the Denver Metro area in April 2008 (73 FR 17897). The revocation was effective November 20, 2008, which is one year after the region’s deferred nonattainment status for the 8-hour ozone standard expired.  The region has attained this standard and has not had a violated since 1987.


State Implementation Plan (SIP) Documents

SIP (48 FR 55284, Dec. 1983)

SIP Revision (60 FR 28055, May 1995)

2001 Ozone Maintenance Plan and Redesignation Request (66 FR 47086, Sep. 2001)


Federal Rules and Actions

Revocation of 1-Hour  Standard for the DM/NFR effective Nov. 20. 2008 (73 FR 17897- April 2, 2008)

Revocation of 1-Hour Standard for all areas in Colorado except the DM/NFR (70 FR 44470 – August 3, 2005)

Designation of Transitional Nonattainment area (56 FR 56694, Nov. 6, 1991)


Other Documents of Interest

Ozone Summary Tables (updated weekly during ozone season)

EPA Approved Statutes and Regulations in the Colorado SIP 

Colorado Air Quality Regulations 


For more information, see RAQC’s “SIP Planning Process and Colorado SIP Summaries” document