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What Does It Mean to Light a Backfire?

Published in Firefighting Tactics 4 mins read

To light a backfire means to intentionally set a controlled fire along a pre-established fireline, typically by wildland firefighters, to consume fuel and/or alter the behavior of an approaching wildfire.

The Purpose and Process of a Backfire

A backfire is a strategic and critical tactic in wildfire management, where a new fire is ignited not to cause damage, but to create a defensive barrier against a larger, uncontrolled blaze.

What is a Backfire?

A backfire is a calculated, defensive fire, rather than a random act of ignition. It is a controlled burn set with a specific objective: to mitigate the spread and intensity of a wildfire that is threatening a particular area or control line.

How Wildland Firefighters Use Backfires

Highly trained wildland firefighters meticulously plan and execute backfires using specialized tools.

  • Method: Firefighters, often armed with tools like a drip torch (a device used to ignite fuels by dripping flammable liquid), carefully ignite vegetation.
  • Location: This controlled fire is strategically set along the inner edge of a pre-existing or constructed fireline – a barrier where fuel has been removed, like a cleared strip of ground, a road, or a river.
  • Objectives: The primary goals for lighting a backfire are twofold:
    • Fuel Consumption: To consume the combustible materials (fuel) that lie directly in the path of the advancing wildfire. By burning this fuel in a controlled manner, the wildfire is deprived of its energy source when it eventually reaches the burned-out area, causing it to slow down or extinguish.
    • Convection Column Alteration: To change the direction or force of the wildfire's convection column. The heat and rising air (convection) from the backfire can draw the larger wildfire towards it, causing the two fires to meet and effectively creating a larger, safer, burned-out zone. This manipulation can also reduce the main fire's intensity and make it easier to manage.

Strategic Importance of Backfires

Backfires are crucial tactics employed in scenarios where direct attack on the wildfire is too dangerous or impractical due to factors like fire intensity, terrain, or wind conditions.

  • Creating a Barrier: The most immediate benefit of a backfire is the creation of a "black line" or "buffer zone" of burned ground ahead of the main wildfire. When the uncontrolled fire reaches this area, it encounters no unburnt fuel, which often causes it to diminish, stall, or stop its forward progress.
  • Manipulating Fire Behavior: The strategic placement and timing of a backfire can profoundly influence how a wildfire behaves. The strong convection currents generated by the backfire can effectively "pull" the main fire's flames and smoke into the backfire, drawing the fire away from vulnerable areas and into a controlled burn area.
  • Enhancing Safety: By managing fire from a distance and on controlled terms, backfiring enhances the safety of firefighting crews, reducing their direct exposure to the most dangerous aspects of an active wildfire front.

Key Aspects of Backfiring

Aspect Description
Who Exclusively carried out by highly trained wildland firefighters, often as part of a larger incident management team.
What An intentionally ignited, controlled fire used as a defensive measure against an uncontrolled wildfire.
Where Set along the interior edge of a fireline (a cleared or natural break in fuel) or other pre-established control lines such as roads, rivers, or existing burned areas.
Why To eliminate fuel from the wildfire's anticipated path and/or to alter the force and direction of the wildfire's convection column, thereby halting or slowing its advance and reducing its destructive potential.
Tools Common tools include drip torches, fusees, and sometimes aerial ignition devices like plastic sphere dispensers (PSD) deployed from helicopters for large-scale operations.

Why Professional Expertise is Essential

Lighting a backfire is a highly complex and risky operation that requires extensive expertise. It demands profound knowledge of fire behavior, precise understanding of weather patterns (especially wind), topography, and the specific types of fuels present. A miscalculation can have severe consequences, potentially leading to the backfire itself becoming uncontrollable or having unintended negative impacts. This underscores why only experienced professionals with specialized training are authorized to undertake this critical and dangerous firefighting strategy.