Wildfire suppression is a complex, multi-layered effort relying on a coordinated response from ground crews, aircraft, and strategic planners. The methods used depend heavily on the fire’s behavior, terrain, weather conditions, and available resources. Firefighting strategies involve techniques designed to halt the fire’s advance across remote and rugged landscapes. The ultimate goal is to contain the perimeter of the fire, allowing the remaining unburned fuel inside the control lines to be consumed safely.
Understanding the Suppression Goal
Every technique used to fight a wildfire is designed to disrupt the chemical process of combustion, known as the fire triangle. This triangle represents the three components required to sustain a fire: heat, fuel, and oxygen. Removing any one of these elements will cause the fire to stop.
Firefighting efforts are categorized by which element they target. Water drops primarily remove heat by cooling the burning material below its ignition temperature. Removing fuel, often referred to as starving the fire, is accomplished by creating physical breaks in vegetation. Limiting oxygen is the least common tactic in wildland environments but can be achieved by applying dirt or specialized foams.
Ground-Based Direct Attack
The most immediate and labor-intensive method is the ground-based direct attack, where crews work right at the fire’s edge to extinguish the active flame front. This tactic is reserved for low-intensity fires, typically those with flame lengths less than four feet, allowing personnel to safely work close to the heat. Hand crews use specialized tools like the Pulaski (an axe and hoe combination) and fire shovels to physically remove vegetation and expose the mineral soil beneath. This process creates a definitive break known as a hand line, which removes the fuel source immediately ahead of the fire.
In contrast, an indirect attack is necessary when the fire intensity is too high for crews to safely approach the perimeter. The hand line is constructed hundreds of feet, or even miles, away from the active flame front, often using natural barriers like roads or rivers as anchor points. This safer distance allows crews to build a containment line that the fire is directed toward, rather than fighting the fire at its hottest point.
Aerial Support and Retardant Use
Aircraft provide support, not to extinguish the entire fire, but to slow its spread and reduce its intensity so ground crews can operate safely. Helicopters, often equipped with external buckets, are primarily used for water drops, providing a direct cooling effect on the flame front or hot spots. This tactical cooling allows crews a window of opportunity to advance their lines.
Fixed-wing aircraft, known as air tankers, deliver fire retardant—a mixture of water, gelling agents, and ammonium salts colored bright red for visibility. This retardant is dropped strategically ahead of the fire’s path to pre-treat the vegetation, not directly onto the flames. The ammonium salts chemically inhibit combustion by promoting char formation when heated, which releases water vapor and carbon dioxide to cool the fuel. Very Large Air Tankers (VLATs) can drop thousands of gallons in a single pass, creating a long, visible barrier that reduces the available fuel. The strategic deployment of these aerial assets buys ground crews the time needed to safely construct and reinforce containment lines.
Creating Strategic Containment Lines
For large, high-intensity fires, strategic control lines are established using heavy machinery to create wide fuel breaks far from the fire’s edge. Bulldozers, often fitted with specialized fire plows, scrape away all vegetation down to the mineral soil, creating a wide path known as a dozer line or catline. These lines can be tens of feet wide, serving as the main barrier against the fire’s forward momentum.
The effectiveness of these containment lines is often reinforced through a technique called a burnout operation, sometimes referred to as back-firing. This involves intentionally setting a controlled, low-intensity fire inside the constructed dozer line, which moves inward toward the main wildfire and consumes the fuel. When the two fires meet, the main fire is deprived of fuel and stops its advance at the wide, already-burned-out zone. Burnout operations are highly regulated and require specific weather conditions and careful planning, as this high-risk, high-reward tactic is often the only way to safely contain massive wildfires.