What is crown fire and what indicators suggest its possibility?

• A. A fire spreading only on the ground; indicators include wet conditions
• B. A fire spreading in the canopy; indicators include ladder fuels, high winds, low humidity, dry crowns, and active crown behavior
• C. Fire confined to a single tree; indicators include low flame height
• D. Fire that only occurs at night; indicators include no sun

Answer: (B)

Crown fire is a wildfire that runs through the forest canopy, igniting treetops and spreading largely in the crowns rather than staying on the ground. You’ll look for ladder fuels—materials that connect surface fuels to the canopy, like shrubs and fallen or dead wood—that let fire climb into the trees. Strong winds push flames and move embers quickly, while low humidity dries fuels and makes canopy ignition easier. Dry crowns mean the needles or needles and twigs in the canopy have very low moisture, increasing the likelihood of crown-to-crown spread. Finally, active crown behavior—visible flames in the canopy, rapid vertical and horizontal spread, and torching events—signals that the fire is operating in the crowns. When these signs occur together, crown fire becomes a real possibility.