How do you measure wildfire containment?

As firefighters continued battling the deadly wildfires in Los Angeles County on Friday, officials shared updates on the status of each fire – including how many acres have been burned and the percentage contained. 

Fueled by powerful Santa Ana winds and extreme drought conditions, most of the towering fires that began on Tuesday were still uncontained days later. 

Here’s what to know about wildfire containment:

What does wildfire containment mean?

A firefighter is seen battling the Palisades Fire. (Credit: CAL Fire / Flickr) 

An active fire is contained through various firefighting strategies to stop the flames from moving in that area, the Western Fire Chiefs Association explains. 

Specifically, it means a control line has been placed around that portion of the wildfire, and hopefully, the flames should not be able to cross. A control line can be manmade or natural barriers, such as a cleared road, a river, a ridge, or even a bulldozed firebreak. 

Wildfire containment is typically shared as a percentage, meaning how much of a fire’s perimeter is surrounded by a control line. For example, if a wildfire is 50% contained, that means control lines around 55% of its perimeter have been established. 

"However, if a fire is 100 percent contained, that does not mean the fire has stopped burning and no longer poses a threat," Western Fire Chiefs Association said. "The Wind and other factors can sometimes cause spotfires to jump these lines."

How do they measure wildfire containment?

The containment percentage of a wildfire is measured both on the ground, using tools such as topographic maps and GPS, as well as overhead, using planes with infrared cameras, according to experts at UC Berkeley. 

U.S. Forest Service aircraft teams and satellite teams from NASA and the National Oceanic and Atmospheric Administration (NOAA) regularly help provide information to fire management teams on the ground.

But better detection doesn’t necessarily mean faster containment, UC Berekley says. The ability for fire to be contained is determined by many factors, such as landscape, moisture content, and wind speed and direction.