How Authorities Define Fire ‘Containment’ and ‘Control’

As wildfires spread across Los Angeles, authorities are struggling to contain the blazes, which the public can track via CAL FIRE, a web service provided by the state’s Department of Forestry and Fire Protection.

As of late Thursday, the Sunset fire in Hollywood Hills, which broke out on Wednesday, has been fully contained, while five other fires—including the first and largest Palisades fire as well as the Eaton, Hurst, Kenneth, and Lidia fires—remain active and uncontrolled (threatening to destroy life, property, and natural resources).

But what does it mean for a fire to be 0% contained—as is the case currently for the Eaton and Kenneth fires—or 6% contained like the Palisades fire, 10% contained like the Hurst fire, or 60% contained like the Lidia fire?

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The National Wildfire Coordinating Group (NWGC) defines wildfire containment as “the status of a wildfire suppression action signifying that a control line has been completed around the fire, and any associated spot fires, which can reasonably be expected to stop the fire’s spread.”

These control lines, according to a CAL FIRE factsheet on the 2021 Caldor fire, can be natural like rivers or man-made like dug-out firebreaks. “Containment is a measure of the amount of line around a wildfire.” For example, if officials state that a fire is 30% contained, that means barriers have been placed around 30% of its perimeter. “It’s as much a measure of linear footage as it is confidence,” the factsheet says.

But 100% containment does not mean the fire is controlled or extinguished. The CAL FIRE factsheet says a 100% contained fire continues to burn in the interior of the control line—“Under predicted circumstances, a fire can be expected to burn to the line, but not beyond”—and that several factors need to be considered, including necessary fire suppression repair work, before closures can safely be lifted.

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Northwest Public Broadcasting explained in 2014 that even fires that are deemed 100% contained could still spread, as strong winds may help the blaze breach control lines. A fire is considered “contained,” according to the non-profit organization Western Fire Chiefs Association (WFCA), if fire officials are confident—albeit not guaranteed—that the flames won’t breach these barriers.

After containing a fire, the next step is to bring it under control, which means that it “has been extinguished along the interior of the control line, with any remaining hot spots cooled down,” according to the WFCA. The NWGC defines “controlled” as “the completion of control line around a fire, any spot fires therefrom, and any interior islands to be saved; burned out any unburned area adjacent to the fire side of the control lines; and cool down all hotspots that are immediate threats to the control line, until the lines can reasonably be expected to hold under the foreseeable conditions.”