Flares: Frequently Asked Questions (FAQs)

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.

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.

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.

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.

What kinds of emissions are vented from flares?

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).

Under what circumstances does flaring occur?

During an emergency caused by an equipment breakdown, power outage or other upset beyond a refinery's control, flares are used to safely burn compressed gases that could otherwise pose potential risks to workers, the community or the environment.

Flares are also used to ensure safety during the startup and shutdown of refinery equipment when gases generated by those processes cannot be safely recycled into the refinery.

Flaring is allowed as necessary during emergencies, but flaring for any other reasons is controlled by South Coast AQMD Rule 1118 - Control of Emissions from Refinery Flares (PDF, 96.4kb).

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 the South Bay region of Los Angeles County.

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.

How can I access technical data that show when and 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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