Wildland Firefighting Practice Exam

What condition can lead to erratic fire behavior in a canyon?

1. Quiet winds

2. High humidity

3. Rapid temperature rise

4. Fresh air being sucked toward the fire

The correct answer is: Fresh air being sucked toward the fire

Erratic fire behavior in a canyon is often influenced by topographical features and atmospheric conditions. The correct choice highlights that fresh air being sucked toward the fire can significantly affect how the fire behaves. Canyons can create wind patterns that are unique due to their shape and varying elevations. As the fire heats the surrounding air, this air becomes less dense and rises. Consequently, cooler, denser air from the surrounding areas is drawn into the canyon towards the fire, contributing to an instable and unpredictable fire environment. This influx of fresh air can increase the intensity of the fire and lead to sudden changes in direction and behavior, often causing erratic flames and hotspots that can jump unexpectedly. In contrast, quieter winds or high humidity typically contribute to more stable fire conditions and may suppress fire spread. A rapid temperature rise might also seem significant; however, it is the change in airflow dynamics caused by the drawing of fresh air that is more directly responsible for causing erratic fire behavior in canyon environments.