Connecticut Severe Ozone Nonattainment Reclassification

February 23, 2023

On November 7, 2022, 43 Connecticut towns were reclassified as severe non-attainment with respect to the 2008 ozone National Ambient Air Quality Standards (NAAQS). The reclassification affects sources located in Fairfield [1], New Haven, and Middlesex Counties and has the potential to trigger permitting (Title V and New Source Review) and require the installation of more stringent control technology.


Title V Permitting

With the reclassification to severe ozone nonattainment, the Title V major source thresholds for nitrogen oxides (NOx) and volatile organic compounds (VOCs), which are ozone precursors, will be lowered from 50 to 25 tons per year. As a result, many facilities in affected counties that were not previously subject to Title V will now be required to submit an initial Title V permit application or establish federally enforceable emission limits (through permitting) to reduce potential emissions below major source thresholds. Title V applications for affected sources must be submitted to the Connecticut Department of Energy and Environmental Protection (CTDEEP) by November 6, 2023. Title V permits may impose additional monitoring, recordkeeping, and reporting requirements including the requirement to submit annual compliance certifications and semiannual deviation reports which require sources to identify any deviations from permit conditions and monitoring system failures. In addition, Title V facilities may be subject to more frequent agency inspections.

Sources that elect to establish a federally enforceable limit may do so by either modifying an existing New Source Review permit to lower potential emissions of NOx and/or VOC below the 25 tons per year major source threshold or limit premises-wide actual emissions per Regulations of Connecticut State Agencies (RCSA) Section 22a-174-33a (below 50 percent of major source thresholds or less than 12.5 tons per year) or RCSA Section 22a-174-33b (below 80 percent of major source thresholds or less than 20 tons per year) [2]. Sources committing to operate a facility under RCSA §22a-174-33a or -33b are required to submit a notification to CTDEEP on the provided forms.

Since the November deadline is less than a year away, now is a good time to review air permits and emission calculations and develop a permitting strategy for complying with the reclassification.


Nonattainment New Source Review Permitting

Similar to Title V, the NOx and VOC major source thresholds for Nonattainment New Source Review air permitting have also been lowered to 25 tons per year [3]. Modifications for major sources located in newly affected areas will be required to undergo Nonattainment New Source Review if potential emissions from the project (plus emissions increases over the last five years) equal or exceed 25 tons per year of NOx or VOC. Nonattainment New Source Review permitting requires the use of the Lowest Achievable Emission Rate and the need to obtain emission offsets at a ratio of 1.3-to-1.


Control Technology Requirements

Major sources of NOx and VOC in Connecticut are already subject to Reasonably Available Control Technology requirements as specified under RCSA Sec. 22a-174e and 22a-174-22f. CTDEEP is in the process of updating these rules and will likely require additional controls for certain sources in affected areas. Revisions to the U.S. Environmental Protection Agency’s Control Techniques Guidelines and Alternative Control Techniques may also impose additional requirements. Sources newly subject to Reasonably Available Control Technology will have three years from the effective date to achieve compliance (November 2025).

CEC has been following the 2008 ozone NAAQS nonattainment redesignations rules in Connecticut and is prepared to assist you with your permitting needs. If you have any questions regarding the ozone reclassifications and how they may affect your operations, please contact our experts:

Jennifer Flannery


Jennifer Flannery | Vice President, Philadelphia Office Lead




Carla Adduci | Air Quality Principal


[1] Connecticut’s former one-hour severe ozone nonattainment area consisted of Fairfield County with the exception of the town of Shelton, plus included Bridgewater and New Milford.

[2] If currently operating under RCSA §22a-174-33a or -33b and actual premises-wide NOx and/or VOC emissions are greater than 20 tons per year, facilities must submit a Notification of Cessation and apply for a Title V permit.

[3] Effective November 7, 2022

About the Author

Carla Adduci

Carla Adduci is a Principal in CEC's Air Quality practice at our Philadelphia office. Her areas of expertise are in air quality engineering, permitting, pollution control, regulatory development, and compliance assistance.

Want more content like this?


Post a Comment

Your email address will not be published. Required fields are marked *