How do firefighters determine the cause of a wildfire?
July 27, 2017
Behind every wildfire is a mystery: How did it start? Was it human-caused? And, if so, who's responsible?
The recent Peak 2 Fire in Summit County, which forced hundreds of residential evacuations and a $2 million bill for emergency services, was found to be the result of two hikers.
But how is that determined?
"Typically the investigation starts the moment we're aware of a fire," said Todd Holzwarth, chief of East Grand Fire Protection District. "Is there any reason we should be having a fire at this point? Is it the Monday after the weekend? Have we had a bunch of lightning the day before? Is it moist or dry out? Is it windy?"
In the event of a wildfire, fire departments immediately get to work to determine the origins of the blaze and the cause. The first step in the process is determining whether the fire was natural or if humans caused it.
Firefighters begin putting together the pieces of how a fire may have started before they are even on scene. By analyzing myriad variables in the area of the fire, officials are able to guess as to whether the fire is human caused or natural.
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A dry, windy day after a thunderstorm could tip off firefighters that the ignition may have been caused by lightning the night before. A fire at a campsite after the weekend likely spells human error.
Holzwarth said that location also plays a major role in the initial investigation, and that fires by the side of the road or near campsites are much more likely to be man-made, while lightning typically causes blazes deep in the woods.
"The easier it is to get to a fire, the more we'll be leaning toward a human having something to do with it," Holzwarth said. "If you can drive almost to the fire, or it's on a trail or camping area, a big light bulb goes off."
A majority of the investigation takes place after the fire has been extinguished.
First responders are responsible for protecting the origin area of the fire until investigators can arrive to begin analyzing the scene.
Investigation into fires on federal lands, however, is the responsibility of a special team of U.S. Forest Service law enforcement officers.
Lauren Pirchner, a wildland fire investigator and Forest Service law enforcement officer for the Sulphur Ranger District in Grand County, has the difficult job of determining the cause and origin of fires on such lands.
Pirchner said that the investigation begins by identifying burn patterns, and looking at angles of char on trees within the fire's progression that can lead back to the fire's origin. Man-made fires often leave a fire ring at the site, she said, where the fire would have escaped, while lightning often leaves a candy cane stripe around the tree where it struck.
Once an origin is determined, investigators begin tracking down those responsible.
"Investigators work closely with potential witnesses and first responders to identify potential suspects," Pirchner said. "The origin is scoured for evidence."
Investigators establish a grid around the origin area and use tools such as magnets, magnifying glasses and hand tools to sift through the dirt for potential evidence. They're primarily looking for common fire starters: matches, cigarettes, fireworks and shell casings.
Holzwarth added that investigators might also analyze tire tracks, which they can tie to specific vehicles.
In certain cases, investigators will collect samples of soil from the origin site to determine if any accelerants such as gasoline were used. If so, the fire may be arson.
While the evidence-collection process is thorough, the actual fighting of the fire often complicates it.
"It gets contaminated," Holzwarth said. "We may have put foam on the evidence while fighting the fire, or there may have been a slurry drop on it."
This means that eyewitness testimony is the most important facet in searching for whomever started the fire. Investigators will interview witnesses, looking for anyone who may have seen a car, license plate or person near a campfire in the area.
Lack or destruction of evidence may mean that eyewitness testimony is the only way to track down the responsible party.
"This depends on the type of evidence left at the scene," Pirchner said. "Was there an entire camp left and were the people gone for the day in town somewhere? Did someone drop a receipt or leave something in an abandoned campfire that did not burn all the way?"
If investigators are able to identify the responsible party, penalties can range from minor civil charges to major criminal charges depending on intent, the size of the fire and the amount of resources used to contain it.
Intent is key as accidental fires, started by failing to fully extinguish a campfire or tossing a cigarette out a window, are typically seen as a misdemeanor with a typical penalty of a few hundred dollars in fines, but can go up to $5,000 and six months in jail.
Anyone caught setting fires purposefully could be sentenced to anywhere from five to 40 years in prison depending on the risk the fire posed to others, including firefighters. If the fire directly or proximately caused the death of any person, the responsible party could face life in prison or even the death penalty, according to the nation's criminal code.
Pirchner stressed that it is the responsibility of everyone who visits national parks or campgrounds to help prevent man-made fires. Visitors should make themselves aware of any fire restrictions in the area, bring excess water to put out their campfire until it is cold to the touch and always report any abandoned campfires they come across.