Chapter 6: How to Say What You Know

A Fire Behavior Language

How Are Predictions Expressed?

To fight fires safely, firefighters must learn to profit from observations of fire behavior and to make “on-the-fire-line” fire behavior predictions. In addition, they must be able to communicate to others the basis or reason for the prediction. Firefighters must learn that change is inevitable, and they must learn to anticipate change if they are to survive in the very hostile environment of wildfires.

In order to anticipate fire behavior changes, we must see clearly the basis for the prediction; and be capable to convey to fire planners and firefighters the prediction and the basis for it. If we are unable to anticipate changes in fire behavior, we limit our own control capabilities by only reacting after the fire behavior change with a greatly reduced margin of safety.

Following are some examples of phrases that should be used to communicate critical information. This language is designed to standardize messages between firefighters and fire overhead personnel

Where is the Fuel on the Flammability Curve?

Is a phrase asking you to identify where the fuel in question is on the flammability curve. Ask if the exposure is, “going up the curve,” “going down the curve,” or at the “peak of the curve.” Observe the time of day, the aspect and the shadow lengths. It does not take long to determine whether the exposure in question is “going up,” “at the peak,” or “coming down” the flammability curve.

It is important to know where the fuel is on the flammability curve to predict how the fire’s intensity and potential could change. If an exposure has not yet reached the pinnacle of its temperature peak there is real potential for the fire behavior to worsen. A fire burning in fuels that are past the crest of the flammability curve will be expected to ease or subside. A fire at the peak of the flammability curve will be at its worst potential.

It is imperative that before attacking any wildfire, one should be aware—and tell others—what the future behavior of the fire will be. It is vital to the selection of successful tactics to know whether the situation is improving or deteriorating. To do less is less than professional.

Hot Fuel / Cold Fuel

In a situation when fire behavior predictions are based upon the fuel’s flammability differences, use the words that help others understand the cause for a fire behavior prediction and tactical change. For example:

If a  lookout reported that there is a spot fire across the line. Now, if the lookout includes the words “in hot fuel” the message conveys a much different meaning than if the lookout reported the spot fire to be in “cold fuel.” Hot fuel denotes danger.

The crew supervisor hearing that the fire has spotted into hot fuel will react to the threat quickly, and without further justification he should predict the potential of more spot fires occurring.

Is the Fuel Flammability Getting Worse or Easing?

Ask that question before attacking the fire. If the flammability is increasing, then it is reasonable to predict the potential fire behavior will become worse.

Fire behavior predictions should include the reason for the predicted change so that others might observe the changing fire intensities and relate to the cause for the changes. The direction of flammability for an incident is an important fact to know and communicate to others during suppression action. It is a factor in planning safe actions and tactics that are appropriate for the duration and location of the fire assignment.

The Forces are IN/OUT of Alignment

This phrase expresses the alignment of wind, slope and fuel flammability. When aligned, the fire intensity is at its maximum. When out of alignment, the intensity is at minimum. This accounts for some variations when atmospheric conditions are not changing.

To convey the alignment of forces, use the phrases “in full alignment,” “out of alignment,” or “half in alignment” to warn of potential changes of fire behavior caused by the degree of alignment of the primary forces, wind, slope and fuel flammability peak.

Over the Threshold of Control

A phrase that expresses a condition of the fire’s behavior that is beyond the capability of the suppression force to control. Use this phrase to explain to others the reason for suggesting a change in tactics that would be more appropriate for an over-threshold fire behavior situation.

In observing the conditions around you and honing your prediction skills, you can recognize where, when and under what conditions the fire behavior is beyond threshold. Learn to recognize the combination of forces that create these events and learn to predict when and where the threshold of control will occur. Again, it is helpful to others to point out the cause, location and period where the wildfire will repeat the over-threshold behavior. To quickly learn to recognize the fire behavior potential, observe the forces, alignments or other factors at work during over-threshold conditions. Learn to classify the exposure fuels by identifying the differences between the areas that are burning differently. Once you learn to read topographical fire behavior potential, you can make fire line predictions with ease. Another example:

The crew lookout calls the crew supervisor and relates that there is now a spot fire over the line. The next message elaborates that the spot fire is in hot fuel, at the peak of the curve, and at the base of a west aspect or hot slope. The crew supervisor knows from recent observations of fire behavior during the day that this situation will result in fire too hot to handle.

It is will be “over threshold fire behavior.” The supervisor should take defensive action and look for the next opportunity when and where the fire will again be within the threshold of control. This is not the time to blindly attack the spot fire. Save strength and resources for battles you can win.

This Assigned Operation Needs a Time Tag

A phrase to express the need to identify the period of time that the tactics planned are valid. Let’s say that the fire behavior conditions indicated the probability that during the shift your area will have over-threshold fire behavior. It is prudent that alternative tactics be selected for that condition and time period. Tactics useful earlier may be unsafe for such time periods as “at the peak of the flammability curve.”

It is helpful for firefighters to hear a comment such as this: “This tactic is valid only until 1200 when the south aspect approaches its peak flammability.”

For instance, the crew lookout has reported spot fires occurring more frequently for the past two hours. The exposure where the crew is working still has open line and fuel flammability has not yet peaked. To help others quickly understand such a situation, it helps to use a simple phrase like:

“This tactic has run out of time.” Indicating that control is marginal, the situation is worsening and that new tactics are required for these degenerating conditions. To continue to apply out-of-time tactics is futile and unsafe. As a supervisor, you should prevent being “run out” of an area by being fire behavior savvy and mentally ahead of the situation. Change your attitude about staying on line until you are run out; this attitude is dangerous.

A phrase to express the need to re-evaluate the designated tactics in light of new or changing conditions. Immediately upon arrival at the scene, firefighters should quickly review the situation to ensure that the tactic or operation is valid for the time frame identified.

You’ll learn more about tactics selection in Chapter 7, but whatever the tactic, you must be able to communicate whether or not the assigned tactics seem appropriate for the upcoming or observed conditions.


Being able to engage a fire and to know and communicate the potential increase or decrease in fire intensity as time passes is vital to the successful adjustment of tactics.

The ability to communicate the cause of fire behavior change is a skill that should be developed.

Based your action upon knowledge of the potential fire behavior of the fire ground.

Copyright © 1991, 2016 by Doug Campbell.

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