Which of the following types of fire behavior indicates high intensity?

High-intensity fire behavior is characterized by rapid spread, significant heat output, and the potential for large flame lengths. Running fire fits this definition, as it refers to a type of fire that is moving quickly through fuel, often driven by wind and topographic features.

In contrast, smoldering fire is typically low in intensity, representing a slow, low-temperature combustion that produces little heat or flame. Creeping fire tends to be a slow-moving fire, which also indicates lower intensity, as it barely moves and produces minimal flame height. Backing fire involves the fire spreading against the wind or down a slope, generally resulting in lower intensity due to its slower rate of spread and reduced heat output compared to running fire.