Firefighters have achieved considerable progress in their work to contain the wildfires that have been raging throughout Southern California over the past week.
Although the fight against the Thomas fire in Ventura County continues to be a titanic effort — the 173,000-acre blaze was only 15 percent contained as of Sunday midday — firefighters have reported significantly better containment percentages for other fires.
Firefighters assigned to Los Angeles County blazes have achieved 90 percent containment of both the Creek and Rye fires, which have respectively burned in the Sylmar and Santa Clarita areas since Tuesday. And in Riverside County, where the Liberty fire flared up Thursday in Murrieta, fire crews accomplished 100 percent against that blaze as of Saturday night.
So, what does “containment” mean? The Los Angeles Fire Department’s @LAFDtalk Twitter account provided an answer Sunday morning when replying to another Twitter user’s question as to why the Skirball fire in the Bel-Air area was not fully contained despite an apparent absence of flames.
Essentially, containment is another word for “surrounded.” Whereas firefighters attacking a structure fire with the likes of hoses and axes will declare a blaze to be “knocked down” after they gain control of the flames, firefighters employing heavy machinery and hand tools to clear vegetation — and thus to deny fuel from a wildfire — use the word containment to describe how much progress they have made hacking and digging a perimeter around a blaze.
“We actually have to put a line all the way around the fire,” Angeles National Forest spokesman Nathan Judy said. Building that line can be accomplished by bulldozers or ground crews with hand tools.
Firefighters can also increase containment percentage by setting up hose lines near a wildfire, Los Angeles Fire Department spokeswoman Margaret Stewart said.
The containment percentage, however, does not necessarily correlate to safety level around the fire zone, she said. That’s because it’s possible for winds to carry burning embers to the other side of a fire break.
Firefighters continue “mopping up” activities after achieving a significant containment percentage. That job requires firefighters to venture some 100 to 300 feet into burned areas to attack any remaining hot spots, Judy said.
Tackling remaining hot spots makes it possible for firefighters to declare a wild fire is “controlled,” according to the National Wildfire Coordinating Group.
Here’s the NWCG’s definitions for the terms “contained,” “controlled” and “out.”
Contained: When firefighters say a fire is “contained” a control line has been completed around the fire which can reasonably be expected to stop the fire’s spread.
Controlled: For a fire to be called “controlled,” firefighters need to have removed any unburnt fuel and cooled down all hot spots adjacent to control lines to the point that they can reasonably be expected to hold.
Out: A fire is considered “out” when no hot spots are detected within containment lines for at least 48 hours.
