What are spot fires primarily caused by?

Spot fires are primarily caused by airborne embers from distant fires. These embers can be carried by wind currents over significant distances and can ignite new fires in areas that may not be immediately near the main fire front. This phenomenon is particularly dangerous as it can create new ignition points in dry or flammable materials, leading to the rapid spread of fire. The ability of embers to travel ahead of a wildfire makes them a critical factor in fire behavior, especially in conditions that favor spotting, such as strong winds and low humidity.

While aerial sparks and ground-level ignitions can cause fires, they typically occur closer to the main fire source, and faulty electrical equipment is mostly associated with initiating fires rather than spreading existing fires. Therefore, understanding the mechanisms of spot fire generation is crucial for effective wildfire mitigation strategies.