Perhaps no word is more misunderstood and misused in discussions of wildfires – even by firefighters themselves – than the word “containment.”

Simply put, the containment percentage is the amount of the fire area that is surrounded by a line that officials believe the flames will not jump.

“To say a fire is 100 percent contained is to say we have a spherical line such as rocks, roads, streets or fire line where there is no combustible material,” said Eric Sherwin, a spokesman for the San Bernardino County Fire Department.

Fire officials calculate the containment percentage by a variety of means. Aircraft crews with cameras and lasers will take measurements, as will firefighters walking the lines with a global positioning system, Sherwin said.

But the word containment requires context.

Theoretically, if firefighters build a big enough line, the fire could still rage out of control, threatening lives and property, yet be mostly contained. The public and even firefighters sometimes get containment and control mixed up, Sherwin said.

Conversely, a fire could be creeping along and no longer posing a threat yet still have a low containment percentage if factors such as terrain make it difficult to build the containment line, Sherwin said.

But generally, as firefighters gain more control of the fire – stopping its spread – the containment percentage will rise, sometimes very quickly in one day.

“Controlled means the fire is 100% contained with no chance of escaping the fire line,” Sherwin said.

Containment will come first, followed by control days, weeks or even months later. Not until rain pours down on a fire will it be declared out, Sherwin said.

“It’s an arduous process that takes time. When you’re talking about men and women carrying shovels to dig those lines, it takes quite a while,” Sherwin said.

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