What Does Wildfire Containment Mean & How is it Measured?

Learn what wildfire containment is, including phases, strategies, and challenges involved in managing wildfires with guidance from the Western Fire Chiefs Association.

Wildfire containment is a critical aspect of firefighting, focusing on strategies fire crews employ to prevent the spread of active fires. Understanding the nuances of wildfire containment is essential, as containment percentages indicate the extent to which a fire is surrounded but can fluctuate due to factors like wind or spot fires.

What is the Definition of Wildfire Containment?

Wildfire containment refers to suppression efforts made by fire crews. An active fire is contained through various firefighting strategies to stop the fire from moving in that area. Containment does not mean safety, it means a control line has been placed around that portion of the fire and fire should not be able to cross.1 However, if a fire is 100 percent contained, that does not mean the fire has stopped burning and no longer poses a threat. Wind and other factors can sometimes cause spotfires to jump these lines.³ This is why containment percentages can sometimes decrease in media releases.

Wildfire Containment vs. Control

As mentioned, containment is usually expressed as a percentage, and it measures how much of a wildfire’s perimeter is surrounded by a control line. For instance, if a wildfire is 25% contained, control lines around 25% of its perimeter have been established. Fire officials only declare an area of a fire as “contained” if they are confident the fire will not surpass the control, although it is not guaranteed. A fire is considered contained when completely encircled by control lines, including any spot fires. While the fire may still be active, it is unlikely to spread further. A controlled fire is contained and has been extinguished along the interior of the control line, with any remaining hot spots cooled down. Under normal conditions, these control lines are expected to prevent the fire from spreading.²

Phases of Wildfire Containment

Crews work to map and find the manageable areas of the fire where they can establish control lines to contain the fire. This is sometimes done through the help of natural firebreaks as well as manmade firebreaks. Firefighters enter the control phase once a fire has been 100 percent contained. This is when firefighters eliminate any fire threat by jumping the containment lines. To do this, crews establish barriers and remove any possible fire fuels and cool hot spots. Once this step has been completed, the threat of the fire diminishes.³

Strategies for Wildfire Containment

Various suppression tactics are used when determining the best route to contain a wildfire. Frequently, wildfires are contained with control lines, also known as firebreaks or fuel breaks. These are constructed or natural barriers designed to prevent the spread of a wildfire. Firefighters sometimes use controlled burns to create these lines by eliminating fuel before the wildfire reaches it.³

Challenges with Wildfire Containment

Suppression costs have more than tripled over the last few decades, rising from $200 million in 1994 to over $466 million in 2023, driven by factors such as pervasive droughts, earlier and faster snowmelt, and extended growing seasons that have turned fire seasons into fire years. Variations in weather and diverse terrains, such as mountainous regions and dense forests, also complicate firefighting efforts and contribute to the rising costs. An abundance of vegetation due to a century of wildfire suppression, population growth, and home construction in wildfire-prone areas, called the wildland-urban interface, has further exacerbated the problem. The spread of invasive annual grasses has caused rangelands to burn more frequently, and insect infestations have increased the amount of dead, standing timber that fuels wildfires.⁴