EPA Quad O, explained: what NSPS OOOO means for your sites
"Quad O" is how everyone says NSPS Subpart OOOO — the EPA New Source Performance Standards that govern emissions from oil and gas equipment. It gets referenced constantly and read almost never. This is the orientation version: what it covers and where it touches your equipment. It is not legal advice — your environmental team and the current rule text are the authority.
The alphabet soup
- OOOO / OOOOa. The original standards (and the methane-focused update) for new and modified sources — well completions, controllers, storage vessels, and leak monitoring.
- OOOOb. The newer standards for sources built or modified more recently — tighter control requirements, restrictions on routine flaring, and a move toward zero-emission pneumatics.
- OOOOc. Emissions guidelines for existing sources, implemented through state plans — which is what brings older equipment into scope over time.
Where it actually touches your equipment
- Control devices. Flares and enclosed combustors used as controls generally have to hit a high control efficiency (commonly at least 95%, and enclosed units are often designed for 98%+). That only counts if the device stays lit and burns clean — which is the flare-vs-combustor and burner-management side we work on.
- Storage tanks. Vessels over the VOC threshold need vapor control and closed vent systems — which means covers and thief hatches that actually seal. A hatch stuck open is a finding.
- Leak monitoring (LDAR). Fugitive-emission surveys on a schedule, with repair timelines — the documentation side trips people up as often as the hardware.
- Pneumatics. The long-term direction is away from gas-driven controllers toward zero-emission options.
What it means day to day
You don't pass an emissions rule once — you keep passing it. The equipment has to keep working and you have to be able to prove it. We handle the side of that we're good at: flare and combustor ignition and burner management, thief hatch service, and BMS service that keeps the controls proving flame and logging it. Your compliance team owns the rule; we keep the hardware honest.
Related guides.
Thief hatches: what they do, why they fail, when to replace
Thief hatches sound boring. They are — until one fails and you get a six-figure call from the environmental team.
Flare vs. combustor vs. enclosed combustor: what's the difference?
They all burn off gas you can't sell or capture. The difference is how completely they burn it, how visible it is, and what the rules in your area will accept.