Colorado’s April 2026 Air Quality Control Commission (AQCC) rulemaking is marking the transition from planning to active implementation of enforceable controls for Priority Toxic Air Contaminants (PTACs). For many facilities, this rulemaking could introduce new pollutant-specific applicability thresholds and compliance obligations that fall outside traditional major source permitting frameworks. The effort, directed by House Bill 22‑1244, represents the state’s first attempt to regulate certain toxic air pollutants and state‑specific control requirements rather than traditional criteria pollutant thresholds alone.
The AQCC is currently considering the proposed PTAC control regulations during its April 2026 rulemaking hearing (April 15-17, 2026). While final requirements have not yet been adopted, the scope and structure of the rulemaking provide meaningful insight into how Colorado intends to regulate toxic air emissions moving forward and why regulated facilities should begin paying close attention now.
Regulatory Background and Scope of the Rulemaking
HB22‑1244, the Public Protections from Toxic Air Contaminants Act, established a new program within the Colorado Department of Public Health and Environment (CDPHE) to identify, evaluate, and regulate toxic air contaminants beyond existing federal programs. Under the statute, AQCC was directed to identify priority toxic air contaminants, adopt health‑based benchmarks for those pollutants, and develop emission control regulations through formal rulemaking.
In January 2025, AQCC identified five priority toxic air contaminants: benzene, formaldehyde, hexavalent chromium compounds, ethylene oxide, and hydrogen sulfide. Health‑based benchmarks for these pollutants were approved in September 2025. CDPHE’s Priority Toxic Air Contaminants program page provides background on this process and the state’s objectives for reducing exposure to these pollutants. The April 2026 rulemaking represents the next step in this program, establishing enforceable emission control requirements for each identified PTAC.
What the April 2026 AQCC Hearing Will Address
During the April 2026 hearing, the AQCC will consider revisions to Regulation Nos. 24, 26, and 30 to establish state‑only emission control regulations and compliance demonstration provisions for PTACs. According to the Division’s petition for proposed rulemaking, the proposed revisions would apply to both new and existing stationary sources emitting PTAC in excess of an established threshold and may include associated reporting provisions intended to address current information gaps. The hearing marks a shift toward pollutant-specific regulation of air toxics, moving beyond traditional criteria pollutant frameworks and major source classifications.
Potential Implications for Oil & Gas and Industrial Sources
The proposed rules are expected to affect approximately 300 facilities statewide. The primary regulated source categories that will be impacted by the proposed regulations include petroleum processing and refining operations, gas-fired stationary spark ignition engines, combustion turbines, chrome plating and anodizing facilities, anaerobic digesters with manure feedstock, asphalt and asphalt roofing product manufacturers, and sterilization facilities. Applicability is based on facility-wide emissions compared against pollutant-specific thresholds, as well as source type. For these source categories, the relevant PTAC emission thresholds for determining applicability to the emission controls include:
- Benzene — petroleum refineries only; no facility-wide emission threshold was adopted. Control requirements apply to the single petroleum refinery source category currently operating in Colorado,
- Hydrogen sulfide (10,000 lb/yr facility-wide threshold) — asphalt/roofing product manufacturers and anaerobic digesters with manure feedstock,
- Formaldehyde (4,000 lb/yr facility-wide threshold) — gas-fired spark ignition engines and combustion turbines. For existing sources, additional location-specific applicability applies to facilities located in or within 1 mile of a “2020 PTAC Cancer Risk Area,” or within 1 mile of an “occupied area” within a disproportionately impacted community,
- Hexavalent chromium compounds (any emission amount) — chrome plating and anodizing facilities,
- Ethylene oxide — sterilization facilities must comply with 40 C.F.R. Part 63, Subpart O; sources with ethylene oxide usage of 400 lb/yr or less are exempt.
Benzene control requirements are narrowly scoped to petroleum refineries; upstream and midstream oil and gas operations are not subject to new benzene limits under this rulemaking, as existing Regulation No. 7 VOC and greenhouse gas reduction requirements are expected to reduce benzene from those sources. Operators should verify which source categories at their facility fall within the adopted scope.
Importantly, PTAC applicability may not align neatly with existing major or minor source distinctions under Regulation No. 3. Facilities operating as synthetic minors or under general permits could still be affected depending on how applicability thresholds and control provisions are finalized.
Because PTAC controls are expected to be pollutant‑specific, facilities may need to evaluate emissions in a way that differs from traditional criteria pollutant analyses. This shift has the potential to influence permitting pathways, compliance strategies, and long‑term operational planning. Facilities with complex emissions profiles, or those located near PTAC Cancer Risk Areas or disproportionately impacted (DI) communities, should pay particular attention as applicability criteria are finalized.
Key Dates and Practical Next Steps
The AQCC PTAC rulemaking hearing is being held April 15–17, 2026. Draft rule language, statements of basis, and staff analyses have been posted to the AQCC’s April rulemaking hearing folder on the CDPHE website.
Facilities should consider taking the following steps now and following the April 2026 rulemaking:
- Review emissions inventories, TAC reports, and APEN submittals for PTAC constituents,
- Confirm calculation methodologies for formaldehyde and hydrogen sulfide,
- Identify emission units likely to be evaluated under PTAC controls,
- Monitor AQCC hearing materials and participation guidance as they are released.
- Review proximity to DI communities where applicable.
Facilities that engage early will be better positioned to understand applicability, evaluate potential compliance pathways, and manage permitting risk as Colorado’s PTAC program moves toward implementation.
Conclusion
As Colorado finalizes PTAC controls through this April 2026 rulemaking, facilities should closely monitor final rule language and related guidance to understand how the adopted requirements may affect permitting and compliance strategies. Trinity will provide an update once the final PTAC rule is adopted, highlighting key requirements, compliance timing, and practical next steps for regulated facilities.
Industrial operators across the regulated source categories should closely evaluate whether their facilities fall within the adopted scope and begin assessing compliance pathways now. While upstream and midstream oil and gas operations are largely exempt from the new benzene requirements, petroleum refineries, facilities with gas-fired engines and turbines, chrome platers, asphalt manufacturers, and other regulated source types should prioritize reviewing applicable requirements as the final rule is adopted. For questions about how the PTAC rulemaking may affect your facility, or for assistance with emissions evaluations and permitting strategy, please contact Trinity’s Denver office at 720.638.7647 for support.
