Fuel Types and Fire Behavior

Fuels can drastically change fire behavior, so firefighters pay close attention to them. Large trees do not catch fire as quickly as grass does, but they burn much longer and hotter than grass. Certain fuels are not very flammable, such as aspen trees or most flowers. Firefighters can plan their fire suppression tactics by taking note of burning fuels. For example, if a fire is burning in grass and sagebrush on flat terrain, firefighters can use wildland fire engines to spray water on the fire. If a fire is burning in tall ponderosa pine in mountainous, steep terrain, firefighters may have to put the fire out using helicopters and by digging fire line with tools.

Fuel Types

Firefighters classify fuels into three different categories: ground fuels, surface fuels, and crown fuels. They categorized them to help with fire suppression tactics and for safety precautions.

Ground Fuels

This vegetation is close to the ground or lying on the ground. Ground fuels include dead grass and leaves; needles, dead branches, twigs, and logs.

Surface Fuels

These plants and trees are closer to the ground, but are not actually lying on the ground. They are usually made up of shrubs, grasses, low-hanging branches and anything not located in the high branches of the trees that may burn. They can also be referred to as “ladder fuels,” because fire can move from ground fuels to surface fuels, then on to crown fuels.

Crown Fuels

Crown fuels are only in the “crowns” or tops, of the trees. They do not touch the ground and are usually the high branches of trees. When a wildfire burns in the tops of the trees, firefighters call it a “crown fire.”