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Flares: Frequently Asked Questions (FAQs)

Refinery Flares (Rule 1118)

What is a flare?

How do flares work?

Why does flaring occur?

What does Rule 1118 require?

How does Rule 1118 reduce flaring emissions?

When are facilities required to notify South Coast AQMD?

How can I find out about flare events when they occur?

What does flaring look like?

What is the difference between smoke and steam?

What kinds of emissions are emitted from flares and how is it measured?

How can I access technical data that shows how much flaring has occurred?

How many flares fall within South Coast AQMD's jurisdiction?


What is a flare?

A flare is a tall stack equipped with a burner, used to destroy any excess gases produced by refineries, sulfur recovery plants, and hydrogen production plants.  Flare systems are in operation all of the time. Most of the time these systems are in standby mode, ready to combust gases as soon as they enter the flare.

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How do flares work?

Oil refining is a dynamic process. Temperatures, pressures and other processing conditions are carefully controlled to maintain steady-state production operations.  When operating conditions in a refinery, sulfur recovery plant, or hydrogen production plant cause the pressure in the plant to rise, valves automatically open to divert the gases to the flare. There, the burning of excess hydrocarbons yields water and carbon dioxide.

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Why does flaring occur?

Flaring occurs under two circumstances: Planned and Unplanned.

Planned Flaring occurs to ensure safety during scheduled maintenance, the startup/shutdown of a process unit, or other activities where a refinery or related source can reasonably anticipate the need to dispose excess gases that cannot be safely recycled into the facility.

Unplanned Flaring occurs to ensure safety during emergencies caused by equipment breakdown, power outage, or other upset beyond a refinery's control. The flares safely burn excess gases that could otherwise pose potential risks to workers, the community, or the environment.

Flaring is allowed as necessary but is controlled by South Coast AQMD Rule 1118 - Control of Emissions from Refinery Flares (PDF, 96.4kb).

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What does Rule 1118 require? 

Each of the facilities subject to this regulation is required to:

    - Maintain a 24-hour public inquiry telephone hotline;
    - Notify South Coast AQMD of flare events (both planned and unplanned);
    - Reduce emissions to meet specific targets;
    - Develop a flare minimization plan if they fail to meet the emission targets
    - Monitor flare emissions; and
    - Submit quarterly emission reports to South Coast AQMD.

Rule 1118 was first adopted in 1998, amended in 2005, and further amended in 2017.

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How does Rule 1118 reduce flaring emissions?

Rule 1118 requires flare operators to meet the following specific targets for sulfur dioxide (based on a million barrels of crude processing capacity for calendar year 2004 as reported to the United States Department of Energy):

    - January 1, 2006: 1.5 tons
    - January 1, 2008: 1.0 ton
    - January 1, 2010:  0.7 tons
    - January 1, 2012:  0.5 tons

Any facility that exceeds these performance targets is required to submit a flare minimization plan and to pay mitigation fees for the excess emissions.

The flare minimization plan is the refinery's strategy to achieve the performance targets and includes refinery equipment improvements or policy and procedure changes to reduce flaring.

In addition, the rule requires facilities subject to the regulation to operate flares in such a manner that minimizes all flaring, and that no vent gas is combusted except during emergencies, shutdowns, startups, turnarounds, or essential operational need.

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When are facilities required to notify South Coast AQMD?

Refineries and related facilities subject to Rule 1118 requirements are required to notify South Coast AQMD of flare events expected to exceed one or more of the following thresholds:

    - 100 pounds of Volatile Organic Compounds (VOCs)
    - 500 pounds of sulfur dioxides (SO2)
    - 500,000 standard cubic feet of gas (scfm) combusted

In addition, the 2017 rule amendment included an addition notification requirement if the flare's daily cumulative vent gas flow exceeds 100,000 standard cubic feet. 

To be considered a Planned Flare event, the facility must notify South Coast AQMD at least 24 hours prior to the start of the flare event and provide a second notification within one hour of the start of the flare event. Any other situation would be considered unplanned flaring, at which point the above notification thresholds apply.

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How can I find out about flare events when they occur?

Facilities with flares maintain 24-hour telephone numbers available to the public to answer questions about flares and flare events.

In addition, these facilities are also required to notify South Coast AQMD of all planned or unplanned flare events that exceed or may exceed either 100 pounds of volatile organic compounds (VOC) or 500 pounds of sulfur dioxide released, or which may exceed 500,000 standard cubic feet of vent gas. In 2017, Rule 1118 was amended to include an addition notification requirement if the flare's daily cumulative vent gas flow exceeds 100,000 standard cubic feet.

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What does flaring look like?

A pilot flame must be lit whenever a flare is in operation so that purge gases (used to keep air out of the flare) and vent gases can be readily combusted. The pilot flame is located at the tip of the flare. When vent gases are combusted in a flare, a  larger flame is generally visible at the flare tip.  Sometimes steam, which is used to help burn the vent gases completely, is also seen at the flare tip.  However, during a flare event when steam cannot be added to the system quickly enough, or if the smokeless capacity of the flare is exceeded, smoke may also be visible at the edge of the flame.

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What is the difference between smoke and steam?

Smoke is combustion-generated particulate matter which becomes entrained in air; the smaller the particle, the longer it is likely to remain suspended in air.  Suspended particulates obscure visibility by refracting (bending) and scattering light. Measuring the density of these particles against a reference standard provides an indication of relative opacity. Whenever smoke is generated during a flaring event, it appears immediately downstream of the flame.

Steam is condensed water vapor that is added to the flare to increase turbulence, thereby improving combustion of vent gases and reducing the potential for smoking.

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How many flares fall within South Coast AQMD's jurisdiction?

Every petroleum refinery operating within the South Coast AQMD's jurisdiction has one or more flares to control emissions from process units, storage vessels, loading operations (such as trucks) and some waste water processes.  At present, 29 such flares are in operation at the seven petroleum refining facilities (at eight locations), two hydrogen plants, and one sulfur recovery plant located within Los Angeles County.

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What kinds of emissions are emitted from flares and how are they measured?

Flare emissions can include oxides of sulfur (SOx), oxides of nitrogen (NOx), particulate matter (PM10), carbon monoxide (CO), and reactive organic gases (ROG) including Volatile Organic Compounds (VOC).

Flare emissions are monitored using Continuous Emissions Monitoring Systems (CEMS) which utilize specialized analyzers to track, calculate, and store relevant data to determine emissions. Therefore, in 2007, South Coast AQMD staff worked with Western State Petroleum Association (WSPA) and its members to conduct a pilot program to use total sulfur analyzers and higher heating value analyzers for flare emissions. These analyzers are now in use. Please refer to the Flare Technology Demonstration page for further information. 

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How can I access technical data that shows how much flaring has occurred?

Rule 1118 requires operators of flares subject to its requirements to monitor vent gas during flaring events and submit the recorded information to South Coast AQMD on a quarterly basis.

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