What 'fire containment' actually means
The major fires burning in Los Angeles are currently 0% contained
One of the terms that authorities use over and over when discussing wildfires is containment. That’s because containment is a critical measure of how much progress they're making at stopping the fire from spreading.
Intuitively, we in the public can understand that a high containment number is a sign that things are going well. A fire that’s 0% contained is out of control, 25% contained means things are heading in the right direction, 80% contained means the battle is almost won. But when authorities say a fire is X% contained, what do they actually mean?
Containment does not mean that a fire has been extinguished. According to the Western Fire Chiefs Association, it refers to the percentage of a fire’s perimeter that firefighters are confident has been blocked from spreading any further in a certain direction. Because fires need to constantly be fed with new fuel to keep burning, stopping them from moving into new territory is a crucial first step to ultimately putting them out.
Containment happens when barriers, known as firebreaks, get in the way of a fire’s forward momentum. Sometimes those barriers are natural, like rivers or terrain without burnable fuel. Firefighters also create their own barriers by digging wide trenches or doing controlled burns in specific areas.
The WFCA emphasizes that “Containment does not mean safety.” Even a fire that is mostly contained still has sections of its perimeter that are advancing unchecked. Fires blocked by firebreaks are also still burning and sometimes can also break containment when winds carry embers into new areas.
Once a fire is 100% contained, meaning its entire perimeter is blocked from expanding, firefighters consider it to be in the “control phase,” where it can be extinguished for good.
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