By Carol Chavez
This week’s installment of Yeah, We Do That!, focuses on the forensic investigation of wildland fires. According to the National Interagency Fire Center, there were 47,579 wild land fires in the United States in 2013 that resulted in over 4 million acres of burned land. Some regions are consistently hit harder than others.
5 states with the most reported wild fires for 2013
CA – 9,907
NC – 3,514
GA – 2,942
OR – 2,848
AZ – 1,756
5 states with the fewest reported wild fires for 2013
HI – 0
DE – 4
MS – 5
RI – 7
NE – 10
Unfortunately, CA is once again experiencing a rash of wildland fires in 2014. As reported in USA Today, a current wildfire in Canyon County has grown to more than 111 square-miles and is threatening more than 2,000 homes. It reportedly has increased 1.5 times its original size overnight. According to California’s Governor this fire is just one of over a dozen currently burning in the State.
When forensic investigators report to the scene of a wildland fire, they are looking for a myriad of clues. They will look for those clues by conducting an origin and cause field investigation. To complete this task, investigators must be familiar with the National Fire Protection Associations Code 921, which sets the bar for scientific based investigation and analysis of fire and explosion incidents.
They must also understand the principle of fire spread. There are three elements required for fire to ignite – these are heat, fuel and an oxidizing agent. When talking about wildland fires, the weather and topography are part of that tetrahedron.
For a wildfire to occur it means that an ignition source has to make contact with host fuel and then have enough heat to raise it to its ignition temperature. The point where this occurs is called the point of origin. The fire will then progress outward from the point of origin.
As the fire progresses it will demonstrate different and distinct characteristics. These are categorized as vectors and include; advancing fire, backing fire and lateral fire. The markings associated with these vectors are indicators that provide clues as to the fires direction of travel. They can generally be identified through visual observation and used in the context of the fire as whole. From these indicators, the investigator can work back to the point of origin. The investigation of a wild land fire is notably different from that of a structural fire in many ways.
However, there are some recognized fire patterns that do apply to both structural and wildland fires. These include things such as depth and angle of char, spalling, v-patterns and other indicators. Also similar in all fire investigations is the need to rely on a systematic approach to the investigation that is based on the scientific method. By applying this methodology the investigator proceeds with an organized and analytic process to determine the origin and cause of the fire.
The accurate and timely investigation of wildland fires can help determine if they were caused by nature and/or man, and if they were accidental or deliberate in nature. The investigation of wildland fires is also instrumental in future fire prevention.