EPA's Air Rules for the Oil & Natural Gas Industry
SUMMARY OF REQUREMENTS FOR EQUIPMENT
AT NATURAL GAS COMPRESSOR STATIONS
Natural gas compressor stations move gas along a pipeline. In addition to compressors,
compressors stations often include equipment to remove and store water vapor, condensate
and other remaining impurities. Equipment and processes at natural gas compressor stations
may be covered by requirements under the New Source Performance Standards (NSPS) for
volatile organic compounds, and the National Emissions Standard for Hazardous Air Pollutants
(NESHAP) for Natural Gas Transmission and Storage. EPA has made a number of changes in the
final rules based on public comments.
NSPS Requirements for Compressors and Pneumatic Controllers Do Not Apply
•	EPA is not finalizing standards for compressors or pneumatic controllers in the transmission
segment of this industry. Based on public comment, the agency concluded it needed
additional information in order to set cost-effective standards for compressors and
controllers in this segment, where VOC content of the gas generally is low.
REQUIREMENTS FOR OTHER EQUIPMENT
NSPS Requirements for Storage Vessels at Compressor Stations
•	Storage tanks at compressor stations are commonly used to store condensate, and water.
New storage tanks with VOC emissions of 6 tons a year or more must reduce VOC emissions
by at least 95 percent. EPA expects this will generally be accomplished by routing emissions
to a combustion device.
o To ensure enough combustion devices are available to meet this requirement, the
final rule provides a one-year phase-in for this requirement.
Air Toxics Requirements for Glycol Dehydrators
•	Glycol dehydrators, used to remove water vapor from gas, are subject to one of two air
toxics standards, depending on their location. Glycol dehydrators located at compressor
stations are subject to the NESHAP for Natural Gas Transmission and Storage.
•	Today's rule retains the existing standards for large glycol dehydrators and sets new
standards for small glycol dehydrators. A glycol dehydrator is used to remove excess water
vapor from natural gas.
o Large dehydrators: The final rule also retains the existing the 1-ton-per year
benzene compliance option for large glycol dehydrators, meaning operators may
reduce benzene emissions from large dehydrators to less than 1 ton per year as an
alternative to reducing total air toxics emissions by 95 percent.
¦ Small dehydrators: A dehydrator is considered small if it has an annual average
natural gas flow rate of less than 283,000 standard cubic meters per day or

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annual average benzene emissions of less than 1 ton.
¦	Both existing and new small glycol dehydrators must meet a unit-specific limit
for emissions of BTEX (benzene, toluene, ethylbenzene and xylene) that is based
on the unit's natural gas throughput and gas composition. The limit is
determined by applying a formula set out in the final rule.
¦	New small glycol dehydrators must comply with the air toxics requirements
immediately upon startup or within 60 days after the final rule is published in the
Federal Register, whichever is later. Existing small glycol dehydrators must
comply within three years after the effective date of the rule. A small glycol
dehydrator is considered existing if construction or reconstruction began before
Aug. 23, 2011.
o Today's air toxics standards apply only to sources that are considered "major
sources" of air toxics. A major source emits 10 or more tons of a single air toxic or 25
tons or more of a combination of toxics in a year.
MORE INFORMATION
• For summary information on requirements for other types of facilities, or to read the final
rules, visit www.epa.gov/airquality/oilandgas

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