FIRE PATTERN INDICATORS CONTINUED RESEARCH WILL REFINE PROCESSES
BY SHAWN ZIMMERMAKER
The National Wildfire Coordinating Group (NWCG) in the United States is an interagency governmental organization that develops wildfire training and qualifications standards.
The NWCG has established working teams and a subcommittee to develop and maintain what has become the internationally recognized NWCG methodology for wildfire investigations. Foundational to this methodology is an understanding of fire pattern indicators, or FPIs.
When historical events can’t be physically witnessed or reproduced, evidence is gathered to reconstruct the past. Like an archeologist examining artifacts to learn about historical events, a wildfire investigator pieces together FPIs to interpret directional travel of fires, and the origin and cause of wildfires.
Whether an archaeologist or investigator, context is crucial. Without context, artifacts or FPIs are just standalone items of evidence. Context provides background information that influences how a scene is interpreted. Wildfire context includes but is not limited to weather, topography, fuels, and suppression actions. When evaluating a wildfire scene, a comprehensive standard approach is required to understand the relationship between FPIs and its overall context.
FPIs are fire effects created during the passage of a wildfire; they are the physical evidence of fire progression and provide information about the fire’s behavior, weather, spread, and intensity. FPIs develop within the localized fire behavior context and applicable fire behavior principles and dynamics. When properly analyzed each FPI reflects the direction of fire progression at its location; each FPI is a valuable tool to locate the origin and cause of a wildfire.
HISTORY
Prior to the 1960s, wildfire investigations were based on a rudimentary understanding of fire dynamics and spoken word within governmental bodies. Investigations were conducted as a cause and origin process to identify causes that could be targeted with fire prevention programs.
As mid-century approached, wildfire investigations began to transition to origin and cause process based on the emergence of a systematic approach and recognition of FPIs.
As the U.S. Forest research facilities became established and expanded, the need for scientific research into forestry and wildfire was recognized, leading to improvements in forest management and conservation and broadening the understanding of fire development and spread.
These research stations also played a significant role in developing science associated with various causes, (exhaust carbon, catalytic converters, bullets, etc).
Over the years, wildfire investigators have relied on the research documented by these facilities for origin and cause determinations. However, some of the material could benefit from an updated evaluation using modern research techniques, and researching previously unexamined wildfire causes and ignition sources.
By the mid-20th century, literature emerged focusing on identifying the origin of wildfires and reflected a shift from a cause-and-origin emphasis to an origin cause methodology; this was propelled by an expanding comprehension of FPIs and their role in locating ignition areas.
HISTORY
1960: According to Richard Ford, retired fire investigator with the California Division of Forestry (CDF), now known as CAL FIRE, up until the early 1960s, wildfire investigation remained largely speculative, lacking scientific methods or analysis and FPIs. Ford believed the focus was often on identifying the cause and origin using cursory evidence and referred to these initial methods as educated guesses. In the summer of 1960, while examining a wildfire, Ford was asked about the direction of grass stems laying on the burned ground; this sparked Ford’s curiosity and drove him to develop a method to determine an accurate ignition area. By 1961, Ford began to understand the grass’s directional clues and established a systematic approach to locating the ignition area of wildfires.
1962: Ford presented an evidence-based wildfire investigation methodology to a group of CDF law enforcement officers at the CDF Ione Fire Academy. Met with skepticism, Ford was challenged to prove the efficacy of his methods by determining the origin of an actual fire. He was successful, and earned recognition for his methodology, which was adopted by colleagues. At the same time, Bill Longacre, a United States Forest Service (USFS) wildfire investigator, was conducting independent research tracking wildfires to their source. By the mid-1960s, Longacre began to share his work with peers. The current NWCG methodology incorporates many of the FPIs traced back to the contributions of Ford and Longacre.
1969: Kirk’s Fire Investigation textbook introduced a seven-page chapter titled Fire Patterns of Outdoor Fire, which presented principles of wildfire behavior and focused on the V patterns of fires spreading uphill without the influence of wind. The method for deducing the direction of fire spread was based on locating the most damaged side of vegetation, which was assumed to be facing the oncoming fire. This edition did not include an analysis of the FPIs introduced by Ford and Longacre.
1971: Ford authored a paper titled Fire Scene Investigation of Grassland and Forest Fires published in Fire and Arson Investigator magazine. The article presented several FPIs, including grass stem fall, char angles, white ash, depth of char, tree trunk and crown charring, foliage freeze, cupping, sooting, and staining.
1978: NWCG published its first major wildfire investigations work titled Wildfire Origin and Cause Determination [NWCG Handbook 1]. The 41-page handbook attempted to systematically document the then recognized FPIs, including eight that were consistent with those presented by Ford in1971. Refinement of what would become the NWCG methodology continued as new knowledge became available through practical field work and research. One example was change to the practice of entering the burn through a backing area, where some FPIs were often more discernable. This occurred after USFS investigator and instructor Lowell Mansfield noticed that students were overrunning ignition areas as they worked from a backing area toward an advancing area, often leading to the degradation of the scene and evidence. Mansfield proposed a new practice of entering the fire scene through an area of advancing fire progression, where FPIs are more demonstrative. He introduced this technique to Ford, who despite initial skepticism, came to agree with Mansfield and included this change in his 1995 book Investigation of Wildfires.
1980: The USFS, National Park Service and the Bureau of Land Management asked the Federal Law Enforcement Training Center (FLETC) to design, develop, and implement the National Wildfire Investigation Training Program (NWITP). By the following year, subject-matter experts had developed a comprehensive peer reviewed training program and conducted its first presentation. The NWITP gained recognition and adoption in the United States and abroad, featuring 12 FPI types in line with the FPIs in the NWCG Handbook 1 and Ford’s 1971 article.
1982: Bob Bourhill from the Oregon Department of Forestry made a significant contribution to wildfire investigation with a research report based on fieldwork, empirical testing, and actual wildfire scenarios. Bourhill’s A Guide to Natural Cover Wildfire, Fire Direction Indicators focused on eight FPIs aligned with those in the NWCG Handbook 1.
1983: An update to Kirk’s Fire Investigation included a new 15-page chapter titled Grass and Wildland Fires and Their Investigation. It presented seven FPIs that mirrored what Bourhill had previously documented and were also integrated into the 1981 NWITP curriculum.
1987: Ford wrote and published Investigation of Wildfires, building on his studies from the 1960s. Ford’s book, which was updated in 1995, helped establish the use of FPIs, a practice adopted by and included in the NWCG methodology, Handbook 1 and the NWITP.
1992: A working team of NWCG subject-matter experts produced a course titled Wildfire Origin and Cause Determination, also referred to as P-151, based on the NWITP and Handbook 1; the course presented 13 FPIs.
The first edition of NFPA 921, Guide for Fire and Explosion Investigations was published, featuring a peer-reviewed section on fire patterns. While primarily addressing structure fires, the standard did not include a specific chapter on wildfire investigation but did introduce the concepts of heat shadowing and protected areas. These concepts, collectively known as the protection process, form the basis of numerous FPIs recognized by the NWCG methodology.
1992-1999: The NWCG P-151 course emphasis on FPIs achieved global reach. In Spain, a training guide titled Investigation of the Causality of Forest Fires, was published in 1999. This manual graphically encapsulated the fundamental concepts of wildland fire behavior and investigative techniques as taught in the P-151 course.
2000: A group of international wildfire investigators recognized a need to revise the existing Handbook 1 and related training course. In response, NWCG chartered a wildland fire investigation working team with instructions to develop a series of wildfire investigation courses. Th included a revision of P-151 that would be replaced by NWCG FI-210 wildland fire origin and cause determination curriculum. The working team, made up of subject-matter experts from the United States, Canada, and Australia, later became the wildfire investigation subcommittee (WFISC).
2001: The peer-reviewed 2001 edition of NFPA 921 included, for the first time, a chapter focused on wildfire investigations. The chapter included sections discussing 12 FPIs consistent with Ford’s 1995 book, and NWCG publications such as NWITP, P-151, and the NWCG Handbook 1.
2005: WFISC released course material titled Wildland Fire Observations and Origin Scene Protection for First Responders FI-110. By May 2005, WFISC released the updated version of Handbook 1, and the FI-210 (40 hours, with an emphasis on field exercises) curriculum that replaced the P-151 course. Both included a detailed discussion of 14 FPIs with Handbook 1 being the source document for the FI-210 curriculum.
2007: WFISC created additional courses expanding the training available to wildfire investigators; these included Wildfire Case Development and a railroad fire course. By 2013, a powerline fire course had also been completed.
2008: Spain released an updated edition of its 1999 wildfire investigation guide, spanning 405 pages. This comprehensive document encompassed topics such as fire pattern analysis and methods for determining the ignition area of wildfires.
The 2008 revision of NFPA 921 included an 11page peer-reviewed introduction to 12 FPIs and basic wildfire behavior principles.
2011: In response to a request from the NFPA technical committee on fire investigation, subject matter experts from the WFISC participated in the revision of the wildfire investigation chapter. This revision marked the beginnings of an alignment between the NWCG and NFPA that continues and included the 2024 revision.
2016: The WFISC published the Guide to Wildland Fire Origin and Cause Determination, which superseded the 2005 edition. This 337-page guide became the cornerstone of the FI-210 curriculum and identified 11 categories of FPIs based on wildfire behavior principles and dynamics. These 11 FPIs have been peer reviewed and tested through decades of field application and validated by live fire exercises, as required by the FI-210 training program.
2022: Assigning a task group of subject matter experts, WFISC began the process of updating the PMS 412 and FI-210.
Matthew Danckwerts, a fire investigator in South Africa, presented a thesis titled Physical patterns and post-hoc measures of wildfire behavior in grassland: Relevance of forensic indicators in wildfire investigations. Danckwerts found ash color, curling, and spalling to be unreliable indicators but grass consumption, stem fall, leeside charring, protection, sooting, and staining to be reliable especially when interpreted in clusters in proximity to each another. He also recognized the need for broad knowledge and understanding of fire behavioral processes when evaluating FPIs.
2023: Albert Simeoni, head of the fire protection engineering department at Worcester Polytechnic Institute, and fellow researchers published an article titled A preliminary study of wildland fire pattern indicator reliability following an experimental fire, in which they concluded, in part, that FPIs are useful tools to determine the direction of fire spread but must be interpreted in the frame of a global analysis. The researchers also found an understanding of fire behavior and dynamics is mandatory to understand FPIs and their underlying uncertainties.
2024: Keith Parker and Vytenis Barbrauskas published an article titled Validation of NWCG wildfire directional indicators in test burns in coastal California in which they concluded, in part, skilled investigators, trained in using FPIs as described by NWCG and taught in FI-210, can use these teachings along with extensive knowledge and experience to regularly produce reliable determinations of an often quite small specific origin area.
2024: WFISC updates were completed, and the revised PMS 412 was made available in March while FI-210 course was pending publication. WFISC recognized the need to accelerate its revision process to every three years. Whereas each update cannot completely capture all possible needs, WFISC recognized the field needs timely updates and improvements to the investigative process. WFISC submitted multiple study proposals, all of which are pending approval for funding.
INTERNATIONAL ADOPTION AND USE
The NWCG methodology and FPIs have been embraced internationally. In 1994, FPIs were introduced in New South Wales and Victoria and by 2000 were formally adopted by most Australian states. Australian-led engagement with South Korean officials in 2005, along with informational sessions with Chinese and Indonesian land managers occurred in 2006. Similarly, an Australian initiated engagement with the Netherlands pioneered the European adoption in 2011, followed by subsequent training in Cyprus, Denmark, Finland, Sweden, Wales, and the United Kingdom. Expansion continued with the inclusion of students from Belgium, Estonia, and France in 2015. The FI-210 methodology was introduced in South Korea in 2015 followed by New Zealand. The use of FPIs, stemming years of successful fire scene examinations in the United States, has been adopted in Australia, Canada, Europe, Belize, Brazil, Bolivia, Chile, Colombia, Ecuador, El Salvador, Greece, Guatemala, Honduras, Jamaica, Lebanon, Mexico, Portugal, and Spain.
REVIEW AND REFINEMENT
Wildfires demand rigorous investigations to determine their origin and cause. The use of FPIs combined with fire context, has been the cornerstone of reliable wildfire investigations for decades and has proven to be a successful tool globally. Fire behavior experts, forensic scientists, and investigators have located origins, collected ignition sources and analyzed FPIs using this accepted methodology. There are many high-profile cases in which this methodology has been successfully applied.
In 2018 investigators used FPIs to identify an ignition area of the Camp fire in California two days prior to viewing images that supported their findings.
A 2019 serial arson investigation in Minnesota used FPIs to identify ignition areas. After an arrest, the arsonist took the investigators to the field to identify exactly where he had ignited fires, which aligned with determined ignition areas.
In 2017 investigators on the Shast-Trinity National Forest identified an ignition area utilizing FPIs. Unknown to investigators, a local agent had interviewed a witness who had taken a photo of the fire when it ignited. The agent did not share that photo with the investigators until after they completed their investigation because he wanted to see if they would get it right. The investigators’ FPI-identified ignition area matched that of the photograph.
In 2017 in Los Angeles County an independent investigator reevaluated a fire after the primary investigator did not locate an origin and determined the cause of the fire to be undetermined. The primary investigator did not use the methodology of FI-210 or PMS 412. The independent investigator did use the FI-210 methodology and identified FPIs still present 14 months after the fire, tracking the fire back to an ignition area. In 2022, a video surfaced taken by a passing motorist that confirmed ignition area was accurately located by the independent investigator.
Despite the success and usefulness of FPIs, the discipline of wildfire investigation must continue to expand to identify and address any potential gaps in the understanding of FPIs and what influences them, improve / refine methodologies and techniques, expand the educational base for future investigators, and create new areas of inquiry or challenge previous assumptions.
FUTURE RESEARCH
The knowledge of FPI formation and dependability largely stems from empirical observations and the consensus among subject-matter experts. However, there is a need for ongoing research to deepen the fundamental understanding of fire dynamics that influence the formation of FPIs and their reliability in specific circumstances.
FPIs require continued research to examine how they manifest in the differing areas of fire progression. In standard fire behavior terminology these areas are known as head fire, flanking fire and backing fire. Within the wildfire investigation field these areas are also recognized as advancing (head), lateral (flank), and backing (backing/heel).
This research is critical regarding variables encountered in fuel, weather, and topography, specifically the influence of fuel load / type, fire duration, fire intensity, fire severity, wind, and the impact of slope.
Incorporating the expertise and experience of seasoned wildfire investigators is crucial to future studies, as their investigation experience will help to validate variables that must be considered in research. Research should also further explore the specific fire behavior that results in each unique FPI and identify factors that may alter their typical formation, along with their reliability under specific influences. Evaluation is also needed to explore expanding additional FPIs beyond the 11 currently recognized.
Continued research – aimed at the scientific community, fire management professionals, and investigators – would yield enhanced validated data that could corroborate the reliability of FPIs which, in turn, could establish more effective fire management and pre-fire mitigation strategies and increase the value of training materials and doctrines employed by wildfire investigators worldwide.
The international use of FPIs when assessed with the methodology as recommended in FI 210, has provided the international wildfire investigation community with a reliable and accepted process to investigate the origin and cause of wildfires for many years.
Ongoing research will play a critical role in improving these practices. The evolving understanding of wildfire behavior and the emergence of wildfire technology along with ongoing research and collaboration will allow for the enhancement of investigations.
Future research will ensure wildfire investigators are informed, adaptable, and confident in their crucial roles of accurately identifying the origin and cause of wildfires they investigate, for the benefit of the communities they serve.
Special thanks to the WFISC for input and support, in particular Jeff Henrick, Richard Woods, Brenda Rice, Ken Ness, Alan Carlson, Gary White, Jim Shanely, Theo Bailey, and Paul Steensland.
