Colorado Regulation 30 PTAC Updates: Formaldehyde Considerations for Upstream and Midstream Oil & Gas Operators

Colorado Department of Public Health & Environment (CDPHE) Regulation 30 (5 CCR 1001-35) is the Colorado Air Quality Control Commission’s (AQCC) rule establishing Health-Based Standards (HBSs) and management frameworks for identified Priority Toxic Air Contaminants (PTACs). On April 2, 2026, CDPHE amended Regulation 30 to adopt measures controlling emissions of five priority toxic air contaminants (PTACs): benzene, ethylene oxide, formaldehyde, hexavalent chromium compounds, and hydrogen sulfide. The regulation updates target key facility types that are known to emit these pollutants.

Updates to Regulation 30 will require a source-wide review of all formaldehyde emissions, along with a location analysis to determine whether the source meets the rule’s proximity-based criteria. For upstream and midstream oil and gas operators, the first step is determining whether those formaldehyde requirements apply at the facility level. If a source is subject to the rule, operators may also need to comply with additional recordkeeping, reporting, testing, monitoring, and inspection requirements beginning January 1, 2027.

Colorado Regulation 30 – Priority Toxic Air Contaminants (PTACs)

Formaldehyde was identified by Colorado as one of five priority air toxics under the state’s broader toxic air contaminants program, and the April 2026 rulemaking translated that designation into source-specific control requirements. CDPHE identifies formaldehyde as a volatile organic compound emitted from fuel combustion sources such as engines, and the updated rule targets source categories that contribute more meaningful outdoor air impacts.

For formaldehyde, applicability is tied not only to emissions, but also to where a source is located relative to cancer risk screening thresholds and disproportionately impacted communities. In practice, that means operators need to understand both how much formaldehyde a stationary source emits and where that source is located before determining whether the rule’s additional requirements apply.

Determining Applicability

Colorado operators must determine and have records of their applicability to these rules no later than January 1, 2027. The graphic below summarizes how to determine whether a facility is subject to the formaldehyde requirements in Regulation 30. It can be used as a screening tool to evaluate emissions, location-based applicability, and the documentation needed to support that determination.

CDPHE provides resources for evaluating proximity to Disproportionately Impacted Communities (DICs) and associated cancer risk on its Air Toxics Resources page. Most census blocks meeting the applicable cancer risk threshold are located within the DJ Basin; however, the Piceance Basin also includes areas warranting operator awareness.

Trihydro has developed a Google Earth file as a convenient alternative for accessing this information. The file displays census blocks that meet the cancer threshold specified in Regulation 30, using data provided by CDPHE.

For existing sources, Colorado’s Toxic Air Contaminant (TAC) report or the most recent Air Pollution Emissions Notice (APEN) provides the most direct basis for evaluating actual formaldehyde emissions. Alternatively, operators may estimate actual formaldehyde emissions using the three-year average of the stationary source’s 2023, 2024, and 2025 TAC reports.

For sources commencing construction and operation after September 1, 2026, forecasted actual emissions and location assessments must be included in permit applications in a division-approved format. Location assessments are required to be conducted within 30 days prior to submitting permit applications for new or modified engines. This requirement applies to all applicable sources, including those below permit thresholds.

Recordkeeping and Reporting

If a source is subject to the formaldehyde requirements, compliance does not stop at the initial applicability review. Operators will need to maintain records supporting how applicability was determined, including actual emissions documentation, location evaluations addressing disproportionately impacted communities and cancer risk screening, TAC reports, and records supporting both actual and forecasted emissions threshold determinations. These documents will form the basis for demonstrating whether a source is subject to Regulation 30 and how that determination was made.

The rule also establishes several reporting deadlines that depend on source status, including:

• Emissions update report due January 1, 2027
• Notices of Applicability
  • New Sources – March 1st of the following year
  • Modified Sources – March 1st of the following year
  • Existing Sources that have not yet commenced operation as of September 1, 2026 – due no later than 60 days after the first twelve months of operation if source-wide actual emissions >4,000 lbs/yr

Exemptions

The rule also includes several exemptions that may limit applicability for certain engines and turbines. The following exemptions apply specifically to reciprocating engines and turbines, as outlined below. In addition, the rule provides an exemption for internal combustion engines that power portable drilling rigs.

Reciprocating engine exemptions include:

• Compression ignition combustion (diesel) engines
• Non-road engines as defined by Regulation Number 3
• Emergency power generators exempt from APEN or construction permit requirements
• If the engine is scheduled to be removed or electrified to comply with Regulation 7, Part B, Section VII
• Regulation 3 exemptions

Turbine exemptions include:

• If the combustion turbine is scheduled to be removed or electrified to comply with Regulation 7, Part B, Section VII

Emissions Limitations

For affected reciprocating internal combustion engines, the applicable emissions limitations are tied to both existing federal air requirements and the engine’s classification under the rule. The summary below first identifies the referenced federal standards and then outlines the associated carbon monoxide reduction thresholds by engine type.

• Federal standards referenced for Reciprocating Internal Combustion Engines (RICE) 
  • New Source Performance Standards (NSPS) JJJJ (JJJJ)  
  • National Emissions Standards for Hazardous Air Pollutants (NESHAP) ZZZZ (ZZZZ)  

• Engine-specific carbon monoxide reduction requirements: 
  • 4SRB stationary RICE:  Reduce CO emissions by at least 90% 
  • 2SLB stationary RICE:  Reduce CO emissions by at least 58%   
  • 4SLB stationary RICE:  Reduce CO emissions by at least 93%

Performance Testing and Monitoring

For affected sources, performance testing and monitoring requirements vary by equipment type and are tied to existing federal air programs. The summary below separates reciprocating engines from turbines and identifies the corresponding federal standards, testing timelines, and monitoring expectations for each.

Reciprocating Internal Combustion Engines (RICE) performance testing and monitoring requirements include:

• Federal Standards (If you’re subject to the 0.4 g/hp-hr emissions limitations)
  • New Source Performance Standards (NSPS) JJJJ (JJJJ)
  • National Emissions Standards for Hazardous Air Pollutants (NESHAP) ZZZZ (ZZZZ)
  • Conduct an initial performance test for carbon monoxide (CO) within 180 days after startup
• Within 6 months of the initial test, conduct semi-annual portable analyzer monitoring for CO

Turbine performance testing and monitoring requirements include:

• Federal Standards
  • NSPS KKKK or NSPS KKKKa
  • NESHAP Subpart YYYY (YYYY)
• For turbines less than 150 MMBtu/hr
  • Conduct an initial CO test within 180 days of startup and quarterly portable analyzer testing thereafter.
• For turbines greater than 150 MMBtu/hr
  • Continuous emission monitoring systems (CEMS) are required and must demonstrate compliance using CO 3-hour rolling averages of 1-hour blocks.
• Formaldehyde testing
  • Conduct an initial and subsequent performance test for formaldehyde within 180 days after startup.

Additional turbine monitoring requirements include:

• If a turbine is using an oxidation catalyst to comply with formaldehyde or CO emissions, operators must continuously monitor the inlet temperature and maintain a 4-hour rolling average within manufacturer’s specifications.
• If a turbine is not using an oxidation catalyst or CEMS to comply with formaldehyde emissions, operators must develop and implement an Operating Parameter Monitoring Plan (OPMP).
  • This plan must be implemented within 30 days after the initial compliance test. An OPMP should include details on:
    • Combustion chamber temperature, turbine load, air-to-fuel ratio, fuel characteristics
    • Allowable operating ranges for each and justification for how they were developed
    • Monitoring equipment, measurement methods, and monitoring frequency for each parameter including calibration, quality assurance, and quality control procedures.
    • Recordkeeping and reporting procedures
• Beginning January 1, 2027, or a calendar year after initial startup, whichever is later, operators must complete annual inspections. These inspections may coincide but include additional requirements than relevant NSPS or NESHAP requirements.

Conclusion

For oil and gas operators affected by Colorado’s formaldehyde updates, early evaluation will be important. Developing a clear understanding of source-wide emissions, confirming whether a facility meets the applicable location-based criteria, and organizing records to support applicability determinations will help position facilities to meet the January 1, 2027, compliance deadline, as well as any associated monitoring, reporting, and control requirements.