Forest Fire_Content Page_Wildfire Types

Types Of Wildfire

Most homes do not burn from high intensity fires. Most of the homes lost to wildfire in our area burn either as a result of surface fires in the wake of the main fire front or from the accumulation of windblown embers in advance of the fire. The recommendations for the Structure Ignition Zone (SIZ) are designed to reduce the risk of ignition as a result of the different types of wildfire listed below.

Surface Fire

Surface fires burn materials laying on or immediately above the ground, including pine needles, leaves, grass, downed logs, stumps, tree limbs and low shrubs. Some surface fires, especially grass or marsh fires, can move very fast and cause injury or even death when they are underestimated. Surface fires can also throw embers. Surface fires can become crown fires in places where there are “ladder fuels” (i.e. branches that extend to the ground and allow a fire to climb up a tree to its crown).

Crown Fire

Crown fires move through the canopy of a forest, burning from one treetop to the next. They can have extremely high flame lengths, which often start spot fires ahead of the fire. Crown fires are the most destructive of all wildfires, able to kill mature trees and shrubs and can spread quickly. To reduce the possibility of a crown fire, thin trees (and remove some if necessary) to keep them well spaced. This is particularly true for evergreens, which should have at least 30 feet between crowns.

Ember Blizzard

Embers are small, hot, smoldering fragments of solid fuel that can travel long distances with the wind and ignite other fuel sources, such as dry grass, leaves, wooden structures and other flammable objects.  The traditional concept of embers is that they are little bits of burning material that get lofted up into the air. In severe fires, embers can fall down on properties like rain.

Properties should be landscaped and maintained in such a way as to reduce the likelihood of wildfire ignition as a result of an ember landing in a place on the property that is conducive to ignition. Sometimes embers smolder in flammable materials for many hours before leading to the ignition of fire on areas such as a roof or deck. Visible flames as a result of embers may not appear until hours after the wildfire flame front has passed.