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Photo by Ryan Kirby
A prescribed fire crew finishes lighting a head fire along a road. The head fire runs with the wind and meets the backing and flanking fires in the middle of the burn unit, essentially burning itself out.
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Anatomy of a burn
By James Earl Kennamer,
Ph.D., NWTF Chief Conservation Officer
There are basically three types of fire used to perform a prescribed burn to benefit wildlife habitat:
Backing Fire
A backing fire is started along the downwind side of a property to widen the downwind firebreak and prevent the fire from jumping the firebreak. It’s a low flame fire that moves into the wind, and its access to fuel is limited. It still can be an intense, yet small fire, effective at killing and controlling hardwood brush and small trees. However, it burns slow. In order to speed up a backing fire, one might employee a flanking fire.
Flanking Fire
A flanking fire is used to “hurry along” a backing fire. Firefighters spread out along the downwind side of the property after the backing fire has advanced into the property and created a sufficient black line. The line of firefighters then advance with torches lit into the wind. If the wind shifts, a flanking fire and even a backing fire can instantly become a head fire, which is why one should closely monitor the weather and its possible effects on a fire.
Head Fire
A head fire is set to run with the wind. It starts upwind of the property and can move very quickly, building speed and intensity as it burns.
A modification of the head fire is the strip head fire, where a firefighter moves in front of the backing fire and sets a head fire parallel to the backing fire. It picks up speed and rolls downwind as a head fire while slowly moving upwind as a second backing fire. Strip head fires are set in lines across the burn unit and have the advantages of a head fire except they will lose intensity as they hit a blackened area and fizzle out.
Most fire managers use all three fires on the same prescribed burn.