EPA Finalizes Revisions to OOOOb/c: What the Latest Changes Mean for Oil and Gas Operators
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On April 4, 2026, the U.S. EPA finalized revisions to portions of the 2024 oil and natural gas regulations under the Clean Air Act, commonly referred to as OOOOb/c. These updates follow industry petitions, additional data submitted after the 2024 rule, and a formal reconsideration process initiated in 2025.
While the structure of the original rule remains in place, several key provisions have been adjusted to address implementation challenges, particularly around flaring and net heating value (NHV) monitoring.
Here is what changed and what it means for your compliance program.
What Changed in OOOOb/c
1. Temporary Flaring Extended to 72 Hours
The allowable duration for temporary flaring of associated gas has been extended from 24 hours to up to 72 hours for troubleshooting and repairs.
The rule also introduces a new "exigent circumstances" provision that grants additional time beyond 72 hours in cases where site access is limited due to:
Severe weather
Personnel shortages
Supply chain constraints
Operators must document and report these events.
2. Adjusted NHV Monitoring Requirements
Operators are no longer required to perform routine Net Heating Value (NHV) sampling for flares or enclosed combustion devices (ECDs) unless conditions exist that could lower heating value, such as the presence of inert gases.
3. Associated Gas Exemption Removed
Additionally, the general exemption from NHV monitoring for associated gas at well sites has been removed. Going forward, associated gas sources will be subject to the same monitoring framework as other affected facilities.
4. Updated Parameters for Alternative Performance Tests
The revised rule also finalizes several updates to the alternative performance test option for both new and existing sources. Specific changes include:
NHV grab sampling can now be conducted upstream of the inlet to the control device.
The performance test window is set to 14 operating days, with weekend and holiday breaks allowed, provided sampling is spaced no more than 3-operating days apart from the previous sampling day.
Block hourly averaging is required for continuous samples.
A one-hour minimum sampling time applies to twice-daily samples, with an exception for sites where low or intermittent flow makes that duration infeasible.
5. Sampling Demonstration Clarification
The finalized rule also adds clarifying language confirming that the sampling demonstration can serve as an alternative to continuous monitoring for all air-assisted and steam-assisted flares and ECDs.
What Has Not Changed
It is important to note that the broader structure of OOOOb/c remains intact:
Performance standards for new, modified, and reconstructed sources still apply
States are still responsible for implementing emissions guidelines for existing sources
Documentation, reporting, and defensibility remain central to compliance
Current Compliance Deadlines
The EPA issued an Interim Final Rule on December 3, 2025, extending several OOOOb compliance deadlines. Those deadlines remain in effect.
What Oil & Gas Operators Should Do Next
Re-evaluate NHV compliance strategies: Determine where sampling is still required and where it may no longer apply
Review flare and ECD operations: Identify scenarios where inert gases or variable gas streams could still trigger monitoring
Update internal procedures and documentation: Especially for flaring events exceeding 72 hours and exigent circumstances
Monitor upcoming rulemaking: The EPA has indicated that additional revisions to the 2024 rule are still under development
Navigating OOOOb Requirements with Alliance
These revisions do not remove compliance obligations, but they do change how those obligations are met once they take effect.
As the June 1, 2026, NHV compliance date approaches, many facilities are operating in a narrow window where the existing requirements remain in effect, even as the EPA has finalized changes that will soon alter monitoring and testing expectations.
Alliance Technical Group helps operators navigate this transition—clarifying what is required today, what will change once the amendments become effective, and how to implement a compliant, defensible approach that minimizes rework and enforcement risk while positioning facilities for the updated rule.