Exploring Different Firing Techniques: Backing Fires and Head Fires
There are several different ways in which fire can be applied to the ground fuels of an area. Each type behaves differently and achieves a specific objective. One type of fire utilized during a prescribed burn event is a backing fire. The backing fire technique is commonly used and has easier ignition than other fire types. Backing fires typically take longer than other fire application techniques so it is able to consume more of the litter and duff understory that can accumulate on the forest floor.
Backing fires move against the wind and move much slower than a fire moving with the wind, which can be seen in head fire application. Backing fires are essential in creating safety zones, which are needed when applying head fires to the other end of the burn unit. Safety zones are areas in which all of the fuels have been consumed, which eliminate the threat of future ignition during the burn event.
For more information on backing fires, please see the Southern Fire Exchange fact sheet.
Exploring Strip-Heading Fires
Strip-heading fires are set upwind of a firebreak and are secured by a either a firebreak or black created from a backing fire. Head-fires are set in strips usually a few chains from one another. Fire crews monitor the fire behavior of the strip and determine the distance between strips to reach desired flame lengths. Topography, weather, and fuel distribution can all affect the behavior of a strip-heading fire, and application techniques are adjusted to achieve desired fire behavior (Waldrop & Goodrick, 2012).
To explore other firing techniques and to learn more about strip-heading fires please see pages 35-41 in the Introduction to Prescribed Fire in Southern Ecosystems.
Waldrop, T. A., & Goodrick, S. L. (2012). Introduction to prescribed fire in Southern ecosystems (pp. 36-37).
Exploring the Flanking Fire Firing Technique
A flank fire is set on the side of a burn unit parallel to the wind. Flank fires neither go against the wind nor with the wind, but are running parallel to the wind direction. Flanking fires are typically used when the objective is to connect a backing fire to the head fire. Flanking fires burn at an intermediate temperature when compared to the cooler backing fire and hot head fire.
To learn more about flanking fires and other firing techniques please see pages 35-41 in the Introduction to Prescribed Fire in Southern Ecosystems.
Point Source, a Fire Application Technique
Fire can be applied on the landscape in many different ways. One firing technique is called a point-source fire, which is used to achieve less intense fire behavior than strip-heading fires. During a burn, weather conditions change and fire crews must adapt firing techniques to minimize extreme fire behavior. Utilizing point-source fires in place of strip-heading fires decreases the intensity of fire behavior and still accomplishes desired goals. Point-source fires, when ignited in a grid, will merge together creating smaller flame lengths than those typically experienced during a strip-heading fire. Point source fires can be modified by spacing each spot fire at varying distances from one another in a grid pattern. Both timing and distance between each individual point-source fire will contribute to the fire behavior, and these variables must be adjusted when changes in fuel composition and weather are encountered (Waldrop & Goodrick, 2012).
To learn more about point-source fires and other firing techniques please see pages 35-41 in the Introduction to Prescribed Fire in Southern Ecosystems.
Waldrop, T. A., & Goodrick, S. L. (2012). Introduction to prescribed fire in Southern ecosystems (pp. 38-39).
Ring Fires, Applying Fire in a Circular Pattern
A ring fire is another use of fire where the applicator applies fire in a circular pattern. Once the ring is set it burns inward to consume all fuels within the ring. Ring fires are typically used when smoke is needed to move upward more quickly than other types. These fires are used when there are smoke sensitive areas nearby such as schools, nursing home, airports, and homes.
For more information about smoke sensitive areas and the health impacts caused from smoke, please see the Southern Fire Exchange fact sheet.