What does it really mean when a wildfire is ‘contained’ or ‘controlled’? Key terms explained

Don Sweeney , Sarah Linn
·2 min read

If a wildfire has been 100 percent contained, does that mean it’s out? What about controlled?

What do those containment percentages in daily fire updates mean, anyway?

The California Department of Forestry and Fire Protection uses a variety of technical firefighting terms in its incident reports on wildfires burning across the state — including the Park Fire near Chico.

As on Tuesday morning, the arson-sparked wildfire had scorched a total of 383,619 acres across Butte, Tehama, Plumas and Shasta counties and was 14% contained, Cal Fire said.

“The perimeter of the Park Fire is 260 miles, which means it has burned more than three times the surface area of Lake Tahoe,” the agency said.

Here’s a basic glossary to terms used to describe wildland fires, according to the National Wildfire Coordinating Group:

A firefighter sets a backfire on the Park Fire on Sunday. The fire in northern California has grown to 373,357 acres, making it the sixth-largest ever wildfire in the state. It is only 12% contained. Photo by John G. Mabanglo/EPA-EFE
A firefighter sets a backfire on the Park Fire on Sunday. The fire in northern California has grown to 373,357 acres, making it the sixth-largest ever wildfire in the state. It is only 12% contained. Photo by John G. Mabanglo/EPA-EFE

What does wildfire containment mean?

Containment, normally expressed as a percentage, indicates how much of the fire has been enclosed by a control line.

A wildfire with 25% containment means control lines have been completed around 25% of the fire’s perimeter.

Control lines are constructed or natural barriers used to stop a wildfire from spreading, also called firebreaks or fuel breaks.

Firefighters sometimes create them with controlled burns to remove fuel before the wildfire reaches it.

What’s the difference between contained and controlled fires?

Controlled fires are not only contained, but have been burned out along the interior of the control line with any hot spots threatening the line cooled down.

The control lines are expected to halt the spread of the fire under reasonable conditions.

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