Fire crews work to put out hot spots in a Fallbrook community that was hit by the Lilac Fire. / Photo by Adriana Heldiz

As soon as a wildfire starts, fire officials start to talk about how much of the fire is “contained.”

On Friday morning, as the Lilac Fire raged in San Diego County, for example, officials and members of the media repeated the ominous statistic that the fire was “zero percent contained.”

Most people assume the number is supposed to mean how much of a fire is out. It doesn’t. So what does it mean?

There’s an official definition, but fire officials don’t always seem to use it, so it may be more art than science when they say something like, “The fire is 15 percent contained.”

Officially, according to Cal Fire, “A fire is contained when it is surrounded on all sides by some kind of boundary but is still burning and has the potential to jump a boundary line.”

Usually, the boundary is something the firefighters have imposed by digging, bulldozing or running a firehouse around the perimeter of a fire. Sometimes the boundary can be natural, like a lake, or artificial, like a road.

But sometimes fire officials takes liberties with the definition, perhaps because most members of the public conflate containment with whether a fire is out.

A fire could be contained and still burning.

Cpt. Kendal Bortisser, a Cal Fire spokesman, said he’s seen fires that are 85 percent or 95 percent contained flare up again and spread.

Likewise, a fire could be zero percent contained even though firefighters have stopped its spread.

That’s what happened on Friday at the Lilac Fire. Firefighters from across the state had impressively stopped the spread of the fire by early morning, but it wasn’t until Friday evening that fire officials said they had any of the fire contained.

It appears that fire officials were using the containment number to lowball their own progress to the public, though in an earnest attempt to control expectations. There were still dangerous hotspots. Even firefighters on the ground who felt they had things contained feared that high winds would rekindle the fire and undo their progress.

At a Saturday night community meeting, the Lilac Fire incident commander, Cal Fire Deputy Chief Bret Gouvea, told evacuees that the fire was 100 percent surrounded, even though it was still officially just 50 percent “contained.”

“It’s always a question: Why is the containment so low?” he said. “We have control lines all the way around this fire, which means the forward progression of the fire has stopped, any spread of the fire has stopped.”

That seems like it might meet the official definition of 100 percent containment.

But he had another definition, one more likely to mean something to the public. Containment is when firefighters “feel very comfortable” that they can walk away from a fire without it escaping.

That definition appears closer to what the public expects the word to mean.

Ry Rivard was formerly a reporter for Voice of San Diego. He wrote about water and power.

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