A backfire or back burn is a fire which is set deliberately in the path of an oncoming fire. As the backfire burns, it consumes fuel, thereby depriving the primary fire of tinder when it reaches the site of the backfire. When the technique is executed correctly, it stops a wildfire in its tracks, or confines it, making it much easier to control. Many firefighters are trained in the art of calculating and placing a backfire when they are taught techniques for fighting wildfires.

The technique is one among an assortment of so-called “fire breaks,” all of which are intended to confine a large wildland fire. Various styles of firebreaks are used, ranging from backfires to simple trenches which are intended to arrest the primary fire. When the decision to set a backfire is placed, it is an acknowledgment that the primary fire is getting out of control, and that it needs to be arrested before it becomes significantly larger.

Setting backfires requires some consideration and calculation. The fire must be far away enough from the primary fire that it creates a dead zone of consumed tinder, rather than merely adding to the larger fire. It must also be optimally positioned, which requires thinking about the movement of the fire through the course of several hours. When set correctly, the winds of the primary fire will suck the backfire inwards, rather than allowing it to spread outwards, but firefighters also need to monitor the line of the backfire to ensure that it does not jump.

Special tools are available to firefighters for the purpose of creating backfires, such as drip torches for quickly and accurately making a line of fire. It is also important for firefighters to wear protective gear when working with a backfire, including heavy fire-resistant pants and jackets and face protection, as a backfire can get very hot. Coordinating efforts when setting a backfire is also important, to ensure that everyone is working with the same information.

Amateurs should not attempt to set back fires, because they can be dangerous. A backfire can spread in the wrong direction, creating a bigger problem, and the fire can also cause severe injuries. Any fire which requires a backfire is generally large enough to need fire professionals, and people should always call for help when they spot wildfires. Even after a fire is out out, firefighters should check the area, to confirm that the fire is not burning under leaves or in thick undergrowth, waiting to spread again.