Protecting the Area of Origin

To know where to look for the evidence, fire investigators learn to “read” burned debris

First-in firefighters often make the difference between a fire investigation that’s never completed and one that is, because they have the luxury of seeing the fire when it’s new, while the head might still be near the origin and before multiple smaller fires combine into one large one. Photo Craig Allyn Rose


By Jim Acker | FireRescue Magazine Volume 5 Issue 6

It’s that time of year again when we start preparing for the wildland fire season, and for many of us that means more wildland/urban interface (WUI) fires.

The 2009 fire season left us with memories of record-breaking fires (such as the Jesusita Fire in Santa Barbara), firefighter and civilian deaths, and extensive property losses. Investigators are still chasing leads and trying to find those responsible for some of last year’s fires.

Although most firefighters concentrate on extinguishing the fire rather than investigating it, once the fire’s out, the investigation takes priority. However, information available at the beginning of the fire can quickly disappear, leaving the investigator with few leads to follow. The point: First-in fire crews often make the difference between a fire investigation that’s never completed and one that is.

As we consider the upcoming WUI/wildland fire season, one item to include in our “mental toolbox” is the duty of the first-in company as it relates to fire investigation. First-in units have the luxury of seeing the fire when it’s still new, while the head might still be near the origin and before multiple smaller fires combine into one large one.

Simply put, first-in units see things that the fire investigator never gets to see. As a result, first-in crews may later be asked to help determine how the fire started. As the WUI expands, many structural firefighters are also tasked with wildland firefighting duties; therefore, a structural firefighter may need to assist with the investigation of a WUI/wildland fire. To put this topic into perspective, in this article, I’ll compare WUI/wildland vs. structural fire investigation, and discuss how to preserve the area of origin in a WUI/wildland fire.

Reading Smoke
Reading smoke is the first step toward discovering what caused a fire or where it started. When approaching a structure fire, the smoke tells us the difference between a lazy fire and a quickly growing fire.

The size and shape of a smoke column during a WUI/wildland fire suggest how long the fire has been burning and how rapidly it started. A fire with a fast start that builds quickly can produce a very definitive top to the smoke column, while a long, smoldering fire often clouds the area with less-definitive drift smoke.

Arriving on Scene
In WUI/wildland fire investigation, noticing a few crucial details early on—such as where the fire is burning, what has already burned and what direction it’s moving—can save you time and effort later. If you create a good mental snapshot of the initial fire, when the time comes to back-track and look for an origin, you’ll most likely be able to narrow your search to a smaller area, making the search much easier.

If you arrive on scene and observe multiple fires, that obviously raises a red flag. Although there are several valid reasons for multiple fire origins, such as downed electrical wires, equipment failures, lightning, etc., multiple origins can also be caused by arson.

When you find multiple origins burning, try to note the location of each one upon your arrival so it’s easier to trace them back once they all burn together. Use any landmark possible (trees, roadways, etc.) to help you remember their initial locations.

Fire Attack
Once the firefighting begins, the differences between structural fire investigation and WUI/wildland fire investigation get a bit blurry. In structural firefighting, hoselines are advanced, and the fire is attacked with more thought to fighting the fire than protecting the origin, which is completely reasonable since the firefighting often takes place in the same room as the origin.

In a WUI/wildland fire situation, however, the fireline is usually a considerable distance from the origin by the time the first water is applied. This gives the investigator a big advantage if crews can fight the fire without tromping through the area of origin.

In both structural and WUI/wildland situations, having a keen eye for the origin and what may have caused the fire is everyone’s responsibility, not just the investigator’s. If the fire was caused by a downed wire that’s now shrouded in smoke, the first-in officer’s quick initial assessment may make note of that detail and could possibly save lives. If the situation allows, the officer should also mark the area of origin with flagging, traffic cones, etc.

Different Environments
In structural firefighting, doors are forced, lines are advanced and crews fight to get to the fire as quickly as possible. Structural firefighters typically enter through the most appropriate door to attack the fire. The area of origin is seldom a concern at this time.

The WUI/wildland firefighter operates within a completely different environment. They can attempt to set the terms of the firefight by drawing firelines where they will be most advantageous to fire crews, which can then be directed along those lines. In terms of the fire investigation, this is a great help because it provides direction to crews that otherwise might unknowingly walk over and destroy critical evidence in the area of origin.

The Challenges of the Job
Fire investigators often have to dig to find the needle of evidence in a haystack of debris. In a structure fire, the desired item can be an appliance, an electrical cord or a candle. Even in the worst cases, those items can survive the firefight and can still be identified by the investigator.

In a WUI/wildland fire, the source can be a tiny piece of hot exhaust carbon, a drop of molten metal from an arced utility line or even a charred matchstick. These items are difficult to find even in an untouched area of origin, so imagine trying to find any one of them after firefighters have dragged hoselines through the area and mixed whatever was left over into the soil.

To know where to look for the evidence, fire investigators learn to “read” burned debris and can follow specific indicators to a small area that surrounds the location where the fire began. Boots, hose and tools can destroy these discrete indicators, making it much harder, if not impossible, to determine even a general area of origin.

What Can You Do?
At all fires, pay attention to what you see and remember it because you may be the only person to see it. Mark the area of origin to protect it, but don’t step inside of it. Steer clear of the area if it’s already marked. If the area is on fire, hit it with a light mist of water, but don’t blast the area with a heavy fire stream. Lastly, let others know the location of the area so that they can also stay clear.

Whether we’re talking structure fires or WUI/wildland fires, we’re in the business of extinguishing fires to save lives and property. And as part of that common objective, we must always keep in mind that learning how today’s fire began can help keep tomorrow’s fires from starting. The first-in officer and crew are many times the keys to making this happen.


Jim Acker is a 29-year veteran of the San Jose (Calif.) Fire Department, where he currently serves as a fire captain. He has more than 10 years of experience as an arson investigator and is certified as a Fire Investigator II in California and a Level III wildland fire investigator by the National Wildfire Coordinating Group. Previously, Acker worked as a firefighter and engineer with the California Department of Forestry and Fire Protection. He teaches and lectures on various fire investigation topics.



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