OOOOb is the U.S. Environmental Protection Agency (EPA) performance standard for crude oil and natural gas facilities built, modified or reconstructed after December 6, 2022 [1]. EPA’s December 2025 rule gave operators until November 30, 2026 to submit all OOOOb annual reports originally due before then, including initial and second reports [2]. The rule is also moving again, with a wider EPA reconsideration proposed on October 29, 2026 [3]. A team choosing a tool now is choosing it for leak surveys that already run, under a rule whose future is open.
OOOOb does not set a single survey schedule for oil and gas sites [4]. It sets six, and which one applies depends on the site’s type, its location and the equipment standing on it [4]. They sit in section 60.5397b of Title 40 of the Code of Federal Regulations (40 CFR), the section on leaking fugitive emissions components [4]. A repair clock with two speeds runs alongside the schedules, and each identified leak starts one [4].
OOOOb compliance software is any tool that tracks those schedules, the repair deadlines each detection starts, and the records proving both. Choosing a tool comes down to two questions: does it record equipment at component level, and can it reconstruct a past site state.
This post covers, in order, what OOOOb requires and where it stands today, what to test in a tool, and how component-level modeling serves both. It is written for environmental and operations staff choosing a tool, and it assumes no background in the rule. OOOOb and OOOOc, its companion guidelines for existing sources, face revision under an October 2026 EPA proposal, so this post describes the rule as written.
What OOOOb Requires as Written
As written, OOOOb requires scheduled leak surveys, repairs inside fixed deadlines, and records proving both [4]. Who the standard covers and which sites it reaches is set out in EPA OOOOb Explained: Who It Covers and What It Requires. The fugitive emissions provisions are the ones that generate recurring work.
Survey Frequency Depends on What Equipment Is at the Site
Single wellhead only well sites and small well sites require surveys at least quarterly, using audible, visual, and olfactory (AVO) or any other detection method [4]. An AVO survey checks for leaks by sound, sight and smell [4].
OGI uses a portable infrared camera that makes otherwise invisible gas visible to the operator [5]. Method 21 is an EPA test method in which a portable instrument detects organic vapor leaks at individual components [6]. Multi-wellhead only well sites require quarterly AVO surveys plus semiannual optical gas imaging (OGI) or Method 21 surveys, spaced four to seven months apart [4].
Well sites and centralized production facilities move to a tighter tier based on the equipment they hold [4]. That tier covers controlled storage vessels, control devices, gas-driven process controllers or pumps, or two or more other pieces of major equipment [4].
Those sites require bimonthly AVO and quarterly OGI or Method 21 [4]. Compressor stations go further still, at monthly AVO and quarterly OGI or Method 21 [4]. Sites on the Alaska North Slope run annually instead, spaced nine to thirteen months apart [4].
You cannot know a site’s survey obligation without an accurate, current inventory of the equipment on it. Adding a single control device or natural gas-driven pump can move a site from quarterly AVO to bimonthly AVO plus quarterly OGI or Method 21. The equipment record is therefore the compliance record, not a separate asset register.
| Site category | AVO survey | OGI or Method 21 survey |
|---|---|---|
| Single wellhead only well site | Quarterly | Not required |
| Small well site | Quarterly, plus thief hatch and dump valve checks where present | Not required |
| Multi-wellhead only well site | Quarterly | Semiannual, 4 to 7 months apart |
| Well site or central production facility with major equipment | Bimonthly | Quarterly, at least 60 days apart |
| Compressor station | Monthly | Quarterly, at least 60 days apart |
| Alaska North Slope site, any type | Not required | Annual OGI or Method 21, 9 to 13 months apart |
The tool below pairs the cadence with the repair clock for any site category.
Two Repair Clocks Run at Different Speeds
Detection starts a clock whose length depends on how the leak was found [4]. A first repair attempt is due within 15 calendar days of an AVO detection [4]. The deadline is 30 calendar days when the detection came from OGI or Method 21 [4]. Final repair follows the same split, at 15 and 30 calendar days after that first attempt [4].
A leak’s first repair attempt is due at 15 or 30 days depending on how it was found, and the completion window doubles likewise. [4]
Where a repair is technically infeasible, unsafe during operation, or needs a blowdown, shutdown or shut-in, it may wait for the next scheduled one [4]. It must happen within two years of detection if that comes first [4]. Tracking that means tracking a two-year horizon per component, against a maintenance schedule.
Where the Rule Stands in November 2026
The survey cadences and repair clocks above are unchanged, though EPA has acted on the rule several times since 2024; the main actions are below.
| Date | EPA action | What it does |
|---|---|---|
| March 8, 2024 | Final OOOOb and OOOOc rule, 89 FR 16820 | Sets the survey, repair and record duties described in this post |
| July 31, 2025 | Interim final rule, 90 FR 35966 | Moves several OOOOb deadlines, including the Super Emitter Program, to January 22, 2027 |
| December 3, 2025 | Final rule, 90 FR 55671 | Keeps those extensions, allows 180 more days for net heating value monitoring, and makes no annual report due before November 30, 2026 |
| April 9, 2026 | Technical reconsideration, 91 FR 18056 | Changes temporary flaring and flare heating value monitoring, and restores annual report contents deleted in error; survey cadences unchanged |
| October 29, 2026 | Proposed wider reconsideration, 91 FR 68234 | Would rescind the Super Emitter Program, subcategorize marginal and conventional well sites, and revise fugitive emissions and other provisions |
Comments on the October 2026 proposal close December 16, 2026 [3]. Until EPA finalizes it, the cadences in the table above still govern.
What to Look for in Emissions Compliance Software
Two properties matter more than any feature list.
Is the Underlying Record the Component or the Site?
A tool that records a site without its equipment categories cannot compute the site’s survey frequency. It also cannot tell you which component started a repair clock.
Subpart W, EPA’s oil and gas greenhouse gas reporting rule, reports leak surveys by component type and site, not by individual component [7]. Component-level emissions attribution therefore needs other records or a model, not the report alone.
Our analysis of TEG dehydrator emissions showed how much a single unit-level number can hide. A triethylene glycol (TEG) dehydrator uses glycol to remove water from gas so it meets pipeline quality standards [8].
Your Records Must Reconstruct a Past Site State
OOOOb requires a written fugitive emissions monitoring plan, and that plan must itself specify which records you keep and for how long [4]. It must also state repair schedules and the procedures used to verify that a repair worked [4]. Reporting and recordkeeping then run through the subpart’s reporting and recordkeeping section, section 60.5420b [4].
Retention is the easy half. A defensible record shows what the site looked like when each survey was performed, as well as what it looks like now. Tools that overwrite site state in place make that history hard to reconstruct.
Both properties are testable in a demo, and the test is more useful than a feature list. Ask the vendor to show each one on their own data rather than describe it.
| Ask the vendor to show you | What it actually tests | The obligation behind it |
|---|---|---|
| A site that gained equipment | Whether frequency derives from equipment records | A control device or gas-driven pump triggers bimonthly AVO, quarterly OGI or Method 21 |
| Site equipment on a past survey date | Whether site state is versioned or overwritten | Records log each survey and date equipment removals and additions |
| One leak found by AVO beside one found by OGI | Whether the two repair clocks are modeled separately | First attempt is due at 15 days for AVO and 30 days for OGI or Method 21 |
| A repair that was deferred rather than completed | Whether delay of repair carries its outer limit | A delayed repair must finish by the next scheduled shutdown, shut-in or blowdown, or within two years, whichever is earliest; a back-ordered part allows 30 days from receipt |
| Where the monitoring plan’s retention terms are enforced | Whether the plan is a document or a control | The plan must state which records are kept and for how long |
A tool that cannot show the first two is not tracking OOOOb, whatever else the feature list carries.
The point where a spreadsheet stops working is not a site count. It is where you can no longer rebuild a past site state by hand. A portfolio whose equipment moves crosses that line well before it becomes large.
Component-Level Modeling Answers Both Questions
TetraSoft MAES, our emissions simulator, models the physics inside equipment instead of multiplying an equipment count by a lookup-table factor [9]. TetraSoft’s MAES page says factor methods assume average throughput, no equipment failures, and stable gas composition [9].
MAES is the Mechanistic Air Emissions Simulator [10]. Its methodology was developed at CSU-METEC, Colorado State University’s (CSU) methane facility, which TetraSoft calls the world’s largest methane detection testing facility [9]. TetraSoft provides access to it through a special license with CSU [9].
The model works from an equipment inventory, gas composition, and operating parameters [9]. It represents the things that go wrong as well, including stuck dump valves, pressure relief events, and thief hatches left open [9]. It generates an expected emission range for a simulated site rather than a single value [11]. A site is described by the equipment actually installed on it, at component level [12].
That equipment inventory holds what OOOOb uses to set well-site survey frequencies, though compressor stations are classed by site type. A site definition listing wellheads, storage vessels with control status, control devices, gas-driven controllers and pumps, and other major equipment contains what frequency determination needs. The quantification and the compliance categorization can then draw on one description of the site instead of two.
MAES models and quantifies emissions from these sources, and survey dispatch is not one of its functions. An inventory model still needs pairing with whatever tool dispatches and logs field surveys. Our standing post on OOOOb/c status for existing sources tracks where each rule sits.
Frequently Asked Questions
Does OOOOb compliance require software?
The rule mandates no compliance software, though annual reports must use the template in EPA’s Compliance and Emissions Data Reporting Interface (CEDRI) [1]. What the rule requires is a written monitoring plan, surveys at the applicable frequency, repairs inside the deadlines, records, and reports [4]. A single site is manageable by hand, and the case for tooling grows with portfolio size and equipment variety.
Is OOOOb still in effect while EPA reconsiders it?
The rule is in force as written, and an October 2026 EPA proposal would revise it. EPA finalized narrow flaring and monitoring changes in April 2026, then proposed wider revisions on October 29, 2026, including rescinding the Super Emitter Program [3]. Treat the status as something to re-check before it drives a spending decision.
How is OOOOb different from Subpart W reporting?
They answer different questions and are not substitutes. OOOOb is a performance standard governing what you must monitor, repair, and control at covered facilities [1]. Subpart W is a greenhouse gas reporting program that quantifies annual emissions from petroleum and natural gas systems [7]. EPA has proposed suspending Subpart W reporting from RY2025 until RY2034 and removing the distribution segment outright; the proposal is not final.
Can one equipment inventory serve both OOOOb and Subpart W?
The physical equipment largely overlaps, so one inventory can feed both, and Subpart W reports onshore production leak surveys for each well-pad site. What differs is what each program does with it. Maintaining two separate equipment lists is how the two records drift apart.
Regulatory requirements in this sector move faster than most compliance calendars. Subscribe for compliance updates and regulatory news.
This post is for informational purposes only and does not constitute legal or compliance advice. Consult qualified legal counsel or a compliance professional for guidance specific to your operations and jurisdiction.
References
- 40 CFR Part 60, Subpart OOOOb, Standards of Performance for Crude Oil and Natural Gas Facilities for Which Construction, Modification or Reconstruction Commenced After December 6, 2022. https://www.ecfr.gov/current/title-40/chapter-I/subchapter-C/part-60/subpart-OOOOb
- EPA, Oil and Natural Gas Sector Climate Review: Extension of Deadlines in Standards of Performance for New, Reconstructed, and Modified Sources and Emissions Guidelines for Existing Sources, final rule, 90 FR 55671, December 3, 2025. https://www.govinfo.gov/content/pkg/FR-2025-12-03/html/2025-21788.htm
- EPA, Additional Reconsideration Standards of Performance for New, Reconstructed, and Modified Sources and Emissions Guidelines for Existing Sources: Oil and Natural Gas Sector Climate Review, proposed rule, 91 FR 68234, October 29, 2026. https://www.govinfo.gov/content/pkg/FR-2026-10-29/html/2026-22082.htm
- 40 CFR 60.5397b, What GHG and VOC standards apply to fugitive emissions components affected facilities. https://www.ecfr.gov/current/title-40/chapter-I/subchapter-C/part-60/section-60.5397b
- 40 CFR Part 60, Appendix K, Determination of Volatile Organic Compound and Greenhouse Gas Leaks Using Optical Gas Imaging. https://www.law.cornell.edu/cfr/text/40/appendix-K_to_part_60
- 40 CFR Part 60, Appendix A-7, Method 21, Determination of Volatile Organic Compound Leaks. https://www.law.cornell.edu/cfr/text/40/appendix-A-7_to_part_60
- 40 CFR Part 98, Subpart W, Mandatory Greenhouse Gas Reporting: Petroleum and Natural Gas Systems. https://www.ecfr.gov/current/title-40/chapter-I/subchapter-C/part-98/subpart-W
- EPA, Natural Gas STAR Program, Glycol Dehydrators. https://www.epa.gov/natural-gas-star-program/glycol-dehydrators
- TetraSoft, MAES Platform. https://tetrasoftco.com/maes-platform/maes-landing.html
- Mdigo et al., Mechanistic Modeling of TEG Dehydrator Emissions in Oil and Gas Industry, Fuels 7(2), 21, 2026, DOI:10.3390/fuels7020021, EEMDL (UT Austin, Colorado State University, Colorado School of Mines).
- CSU METEC, Measurement-Informed Inventory. https://metec.colostate.edu/measurement-informed-inventory/
- Santos et al., Using Measurement-Informed Inventory to Assess Emissions in the Denver-Julesburg Basin, ACS ES&T Air 2, 1598-1611, 2025, DOI:10.1021/acsestair.5c00089.
- EPA, Reconsideration of Standards of Performance for New, Reconstructed, and Modified Sources and Emissions Guidelines for Existing Sources: Oil and Natural Gas Sector Climate Review, final rule, 91 FR 18056, April 9, 2026, effective June 8, 2026. https://www.govinfo.gov/content/pkg/FR-2026-04-09/html/2026-06808.htm
- EPA, 2026 Actions to Reduce Burden on the Oil and Natural Gas Industry. https://www.epa.gov/controlling-air-pollution-oil-and-natural-gas-operations/2026-actions-reduce-burden-oil-and-natural
- EPA, Extension of Deadlines in Standards of Performance for New, Reconstructed, and Modified Sources and Emissions Guidelines for Existing Sources: Oil and Natural Gas Sector Climate Review, interim final rule, 90 FR 35966, July 31, 2025. https://www.govinfo.gov/content/pkg/FR-2025-07-31/html/2025-14531.htm
- 40 CFR 60.5420b, What are my notification, reporting, and recordkeeping requirements? https://www.law.cornell.edu/cfr/text/40/60.5420b
- EPA, Reconsideration of the Greenhouse Gas Reporting Program, proposed rule, 90 FR 44591, September 16, 2025. https://www.federalregister.gov/documents/full_text/text/2025/09/16/2025-17923.txt
Interactive tool
OOOOb survey and repair-clock scheduler
The survey cadence is set by what stands on the site; the repair deadline is set by how the leak was found. Pick both and read the schedule the rule assigns, with the paragraph each number comes from.
Survey cadence
Bimonthly AVO + quarterly OGI
- Bimonthly audio, visual and olfactory survey · (g)(1)(iv)(E)
- Quarterly OGI or Method 21 survey, consecutive surveys at least 60 calendar days apart · (g)(1)(iv)(F)
Repair clock
OGI or Method 21 detectionFirst attempt within 30 calendar days of detection ((h)(1)(ii)); repair complete no later than 30 calendar days after the first attempt ((h)(2)).
- Thief hatches and other openings on storage vessels, and all separator dump valves, are visually inspected in conjunction with each survey.
- The quarterly OGI requirement is waived for a quarter whose average month temperature is below 0°F for two of its three months, but never for two consecutive quarters ((g)(4)).
What counts as major production equipment
Any one of these puts a well site or centralized production facility on the bimonthly-AVO, quarterly-OGI tier ((g)(1)(iv)(A)-(D)):
- One or more controlled storage vessels or tank batteries
- One or more control devices
- One or more natural gas-driven process controllers or pumps
- Two or more other pieces of major production and processing equipment
When a repair can wait
- A repair that is technically infeasible, needs a vent blowdown, a compressor station or well shutdown, a well shut-in, or is unsafe during operation completes at the next scheduled shutdown, shut-in or scheduled vent blowdown, or within 2 years of detection, whichever is earliest ((h)(3)(i)).
- An unavailable replacement part must be ordered within 10 calendar days of the first attempt, and the repair completed no later than 30 calendar days after receipt unless it requires a shutdown ((h)(3)(ii)).
- Every repaired component is resurveyed to confirm the repair worked ((h)(4)).
Frequencies and deadlines from 40 CFR 60.5397b, monitoring frequency at (g) and repairs at (h), read against the CFR annual edition (7-1-25). OOOOb is under EPA reconsideration (91 FR 18056, April 9, 2026). This tool describes the rule as written. A starting point, not a compliance determination. Nothing leaves your browser.
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