Colorado AQCC Adopts First-Ever PTAC Emission Control Regulations: What Facilities Need to Know

On April 17, 2026, the Colorado Air Quality Control Commission (AQCC) adopted final emission control regulations for five Priority Toxic Air Contaminants (PTACs): benzene, formaldehyde, hexavalent chromium compounds, ethylene oxide, and hydrogen sulfide. This rulemaking marks the latest step in a 15-month rulemaking process initiated by House Bill 22‑1244 and represents Colorado’s first enforceable, pollutant-specific emission controls for air toxics, a significant departure from the state’s traditional criteria pollutant framework. The effective date of the revised Regulation 30 and revised Regulation 24 is June 14, 2026.

Approximately 300 facilities statewide are expected to be subject to the new regulations (based on AQCC estimates). Both new and existing sources are covered, with more stringent requirements applied to new or modified sources. The rules also prioritize emissions reductions near disproportionately impacted communities (DICs) and areas identified as PTAC Cancer Risk Areas. Affected facilities should begin assessing applicability and compliance pathways now, as initial compliance deadlines begin as early as June 2026 (hydrogen sulfide and hexavalent chromium sources).

What Was Adopted: Pollutant-by-Pollutant Summary

The adopted regulations under Regulation Nos. 24, 26, and 30 establish distinct compliance requirements for each PTAC.

• Benzene — Petroleum Refineries Only. Benzene controls apply exclusively to petroleum refineries with no facility-wide emissions threshold. Upstream and midstream oil and gas operations are exempt, as existing Regulation No. 7 VOC requirements are expected to reduce benzene from those sources. Benzene control requirements for Petroleum Refineries are contained the revised Regulation Number 24, Part B, Section VI.C (effective June 14, 2026):
  • The primary compliance mechanism is a lower leak detection and repair (LDAR) threshold: pump detection limits are lowered from 10,000 to 2,000 ppmv, and all other covered components are lowered from 10,000 to 500 ppmv.
  • The new LDAR threshold for pumps takes effect June 14, 2026, while a phased compliance timeline applies to non-pump components at existing sources: 10,000 ppmv beginning on 6/14/2026; 1,000 ppmv on 6/30/2027; and 500 ppmv on 6/30/2028.
  • The AQCC directed the APCD to report on benzene reductions by August 2028 and assess whether additional controls are warranted.

• Formaldehyde — 4,000 lb/yr Threshold with Location-Based Applicability. Regulated sources include stationary sources operating spark ignition reciprocating internal combustion engines (SI RICE) or stationary combustion turbines that emit greater than 4,000 lb/yr of formaldehyde facility-wide. The regulations only apply to existing and modified sources if the stationary source is located in or within one mile of a 2020 PTAC Cancer Risk Area or an occupied area within the boundary of a DIC. New sources do not have additional location criteria to determine applicability.
  • Existing sources (commence construction before September 1, 2026) must use the highest actual formaldehyde emissions of the 2023-2025 TAC reports or most recent APEN, with an option to average the three years of reported emissions to determine applicability.
    • Stationary sources that commence construction before September 1, 2026 but do not operate until after this date must determine actual emissions based on the first 12 months after commencing operation.
  • New and modified sources (commence construction on or after September 1, 2026) must use forecasted actual emissions to determine applicability.
  • Sources should pay close attention to recordkeeping and reporting requirements relating to applicability for new, modified, and existing sources.
  • Existing SI RICE must comply with applicable limitations and requirements in 40 CFR Part 63, Subpart ZZZZ and 40 CRF Part 60, Subpart JJJJ. Regulation 30 contains emission limitations for new SI RICE rated > 100 hp. Regulation 3 also contains requirements for annual inspections and adjustments that generally align with NSPS and NESHAP requirements.
  • Existing turbines at major HAP sources must comply with applicable formaldehyde emission limits and operating limits contained in 40 CFR Part 63, Subpart YYYY. Regulation 30 contains emission limitations for new turbines not subject to 40 CFR Subpart YYYY. Additionally, the rule contains operation and maintenance requirements, annual inspection and tuning requirements, and compliance monitoring and performance testing requirements.
  • The deadline to achieve compliance is January 1, 2027 for existing sources that commence construction and operation before September 1, 2026. Sources that commence operation after September 1, 2026 must be in compliance upon the start of operation.
  • The PTAC Cancer Risk Area mapping tool is expected to be released in July 2026.

• Hydrogen Sulfide — 10,000 lb/yr Threshold. Regulated sources include asphalt processing and asphalt roofing product facilities and facilities operating anaerobic digesters that emit greater than 10,000 lb/yr of hydrogen sulfide (H2S) facility-wide.
  • Existing sources (sources that commence construction on or after June 14, 2026) must determine applicability by June 30, 2026, using the highest actual H2S emissions of the 2023–2025 TAC reports or most recent APEN, with an option to average the three years of TAC report emissions.
  • New and modified sources must use forecasted actual emissions; if actual post-startup emissions exceed the forecast, the source is required to notify the Division and has 180 additional days after notification to come into compliance.
  • Sources subject to these controls must install emission control devices capable of achieving at least 97% destruction efficiency. Anaerobic digesters must continuously inject non-corrosive, hydrogen sulfide reducing additive directly into the liquid slurry of the manure receiving pit to limit H₂S concentrations to 500 ppm prior to the abatement device. Additionally, anaerobic digesters must adhere to the best management practices to minimize H2S emissions as detailed in in Regulation 30, Part B, Section III.E.5.b.
  • If actual emissions meet or exceed the threshold in a subsequent year, notification is due to the Division by March 1 of the following year.

• Hexavalent Chromium. Hexavalent chromium control regulations apply to chrome plating and anodizing facilities with no facility-wide emissions threshold. Equipment or activities that are not required to be reported on TAC reports are not subject to the requirements in Regulation 30, Part B, Section III.B.
  • New and expanded decorative chrome plating operations are prohibited from using hexavalent chromium after June 14, 2026.
  • Existing decorative and all functional plating and anodizing operations must implement work practices, install building enclosures to reduce fugitive emissions, use approved suppressants, and comply with enhanced testing, reporting, and recordkeeping requirements.

• Ethylene Oxide. Sterilization facilities are subject to the ethylene oxide control regulations with no facility-wide emissions threshold. The regulations increase the stringency of existing emission limits for abatement equipment and establish new limits for fugitive releases, aligning closely with federal requirements under 40 C.F.R. Part 63, Subpart O.
  • Small sources using less than 400 lb/yr of Ethylene Oxide are exempt and may use periodic testing in lieu of continuous emissions monitoring systems (CEMS). Other sterlization facilities must meet enhanced CEMS-based monitoring requirements beginning on July 1, 2026.

Compliance Timeline and Practical Next Steps

Facilities that emit at least one of the five PTACs in the applicable industry types with TAC emissions above applicable thresholds must begin preparing for compliance. Initial deadlines begin as early as June 2026. The full text of the adopted regulations will be published in the Colorado Register and can be tracked through the CDPHE Priority Toxic Air Contaminants program page. Affected facilities should consider taking the following steps now:

• Confirm whether your facility is a regulated source type for one or more PTACs and, if there is an emissions threshold, calculate facility-wide emissions to determine if applicable thresholds are exceeded.
• For formaldehyde sources, assess proximity to DICs and PTAC Cancer Risk Areas to determine location-based applicability for existing equipment.
• Review TAC emissions reports, APEN submittals, and AP-42 calculation methodologies to ensure emissions estimates are current and defensible.
• Begin evaluating available control technologies and compliance strategies, particularly for formaldehyde (engines/turbines), hydrogen sulfide (asphalt/digesters), and hexavalent chromium (chrome plating).

Conclusion

Colorado’s adoption of PTAC emission controls sets a new baseline for how stationary sources must manage toxic air emissions. For the approximately 300 facilities now subject to these rules, the path forward requires an assessment of applicability, emissions data quality, and compliance feasibility. Facilities should begin that assessment now, particularly for engines, turbines, asphalt operations, chrome plating, and other PTAC-regulated source types. Trinity’s Denver office has been closely tracking the PTAC rulemaking process. For context on the earlier steps in this program, see our previous article, Clearing the Air: Colorado’s 2025 Toxic Air Contaminants Rulemakings.

For questions about how the adopted PTAC regulations affect your facility, or for assistance with emissions evaluations, applicability determinations, and compliance strategy, please contact Kendall Maffet in Trinity’s Denver office at 720.638.7647.