NSPS OOOO / OOOOa / OOOOb / OOOOc (Quad O) Requirements: A Compliance Checklist

NSPS Quad O is the set of EPA air rules that most directly shapes day-to-day compliance for Texas oil and gas operators. The rules, Subparts OOOO, OOOOa, and now OOOOb and OOOOc, control VOC and methane emissions from wells, tanks, pneumatics, compressors, and equipment leaks. Getting the applicable subpart wrong, or missing an LDAR deadline, is one of the more expensive mistakes an operator can make, since fines run into the tens of thousands of dollars per day per violation. This checklist covers which subpart applies to you, what each requires, and what the 2024 methane rules add.

What are NSPS OOOO and OOOOa (Quad O)?

NSPS OOOO and OOOOa are the EPA's performance standards for new, modified, or reconstructed oil and gas facilities, issued under the Clean Air Act. They are often grouped together, but their scope differs: OOOO ("Quad O") set the original VOC controls, and OOOOa ("Quad Oa") added methane and, most importantly for operators, a mandatory Leak Detection and Repair program.

Which Quad O subpart applies to my facility?

The applicable subpart is set by when your source was built, modified, or reconstructed. Getting this determination right is the first step, because it dictates every control and deadline that follows. Note that a "modification," such as fracturing or refracturing a well, can pull an older source into a newer subpart.

You can check your applicable subpart and monitoring schedule in minutes with our free Quad O / LDAR compliance calculator.

What does Quad O require? A compliance checklist

Once you have confirmed applicability, the rules impose specific, documentable controls on the equipment at each site. The steps below distill the core operational requirements for a Texas facility.

Step 1: Inventory your regulated sources

Identify every source the rule reaches at each site: wellheads, storage vessels, pneumatic controllers and pumps, compressors, and fugitive-emission components. An incomplete inventory is the most common root cause of an applicability error.

Step 2: Apply the source-specific controls

Storage vessels

• A storage vessel with a potential to emit of 6 tons per year or more of VOCs requires emission controls. Run this calculation for each vessel.
• Controls must reduce VOC emissions by 95 percent or more, typically by routing vapors to an enclosed combustor or a vapor recovery unit (VRU).
• In Texas, align your control methods and records with RRC Statewide Rule 36 so state and federal documentation do not conflict.

Pneumatic controllers

• At onshore natural gas processing plants, controllers must be zero-bleed. In other segments, they must be low-bleed, at 6 standard cubic feet per hour or less.
• Inventory every controller, document each unit's bleed rate, and set a replacement schedule for non-compliant devices.

Fugitive emissions (LDAR)

The LDAR program is the heart of OOOOa compliance. Well sites and compressor stations must run a formal, documented monitoring program.

Compressors

• Reciprocating: replace rod packing every 26,000 hours or 36 months, or route rod-packing emissions to a control device at 95 percent efficiency.
• Centrifugal: equip wet seal systems with a vapor recovery system capturing emissions at 95 percent efficiency.

Step 3: Keep the records that prove it

To a regulator, an undocumented control does not exist. Maintain LDAR survey logs (date, operator, equipment, leaks found with OGI evidence, and repair timelines), submit annual reports to the EPA through the CDX/CEDRI system, and keep a running modification log so you can prove or disprove applicability for newer subparts.

What do NSPS OOOOb and OOOOc add? The newer methane rules

In 2024, the EPA finalized two new subparts that extend the Quad O framework: NSPS OOOOb and Emission Guidelines OOOOc. Together they represent the most significant tightening of oil and gas air standards since OOOOa, and the first question every Texas operator should answer is which one applies to them.

• NSPS OOOOb applies to sources that are new, modified, or reconstructed after December 6, 2022. Like OOOOa before it, it is a direct federal standard for affected new sources.
• Emission Guidelines OOOOc covers existing sources. Rather than applying directly, OOOOc is implemented through state plans. Texas develops a plan, through the TCEQ and RRC, that sets the compliance timeline for existing sources, so your obligations under OOOOc depend on the approved state plan rather than a single federal date.

The practical changes that matter most to operators include:

• Zero-emission pneumatics: a move away from natural-gas-driven pneumatic controllers and pumps toward zero-emission equipment, phased in over time.
• Stronger fugitive monitoring: more rigorous LDAR monitoring at well sites and compressor stations, with new flexibility to use advanced detection methods such as aerial and satellite screening alongside OGI and Method 21.
• Associated gas limits: restrictions on the routine flaring and venting of associated gas from oil wells, pushing operators toward capture.
• The Super Emitter Program: qualified third parties can notify the EPA of large emission events, on the order of 100 kilograms per hour of methane, which the operator must then investigate and address.
• Expanded storage vessel and compressor standards, along with eventual requirements around well closure.

Implementation of these rules, and the OOOOc state-plan timelines in particular, is still phasing in and has been subject to ongoing review, so applicable dates should be confirmed against the current rule and the Texas state plan before you act.

How Tektite helps with Quad O compliance

Managing OOOO, OOOOa, and the newer OOOOb/OOOOc requirements alongside RRC rules and OSHA safety is where gaps creep in, especially when different vendors handle different pieces. Tektite builds and runs LDAR programs for Texas operators end to end: applicability determination, monitoring, repair tracking, and the annual EPA reporting, coordinated with your SPCC and air-permitting obligations so the records line up. If you are unsure which subpart your sites fall under or whether your program is current, a short review will tell you where you stand.