Guides

Fire investigation guides and references

Reference material for working fire investigators. Scene indicators, documentation, and keeping a determination defensible.

What an origin and cause report is

An NFPA 921 origin and cause report is the written record of a fire investigation. It documents the scene as found, the data collected, the analysis performed, and the determinations the investigator reached: area of origin, cause, and classification. NFPA 921, the Guide for Fire and Explosion Investigations, sets the recognized methodology. NFPA 1033 sets the qualifications of the investigator who signs the report. Attorneys, carriers, and opposing experts read the finished document against both.

The systematic method

Every guide on this page assumes the same process. Recognize the need. Define the problem. Collect data. Analyze the data. Develop a hypothesis. Test the hypothesis against all of the evidence, including the evidence that points elsewhere. A determination that survives testing gets stated to a reasonable degree of professional certainty. When the data supports no determination, the correct finding is undetermined, stated plainly.

The method fixes the order of work. Documentation precedes excavation. Excavation precedes hypothesis. Hypothesis precedes the written conclusion. That order is the first thing opposing counsel tests.

How the ten guides fit together

Two guides cover the report itself: the step-by-step writing guide and the insurance and subrogation guide. Three cover methods that support the analysis: arc mapping, ignitable liquid residue sampling, and the systematic vehicle examination. Three cover ignition scenarios investigators are working now: lithium-ion battery packs, e-bikes and scooters, and CSST arc perforation in lightning events. Two cover the conditions around the work: fatal fires and spoliation of evidence.

Each guide stands alone as a field reference. Start with the writing guide. Pull the rest as the case type comes up.

Car56 drafts the NFPA 921 report from your scene documentation. Every determination in it is yours.

The guides

Lithium-ion battery firesThermal runaway leaves distinct evidence: vent marks, ejected cells, and localized damage at the pack. Covers scene indicators, cell recovery, and the documentation that keeps a battery finding defensible. E-bike and scooter firesMicromobility packs fail during charging, after impact damage, and with mismatched aftermarket chargers. Covers pack and charger examination, cordage, and the egress questions these fires raise. Arc mappingArc sites plotted on a scaled diagram can help bound the area where fire reached energized wiring. Covers arc severing versus fire melting, circuit tracing to the panel, and the limits of the sequencing inference. Ignitable liquid residueWhere to sample, which containers preserve volatiles, and the value of comparison samples. Covers collection technique and what a laboratory result supports in the written report. Vehicle firesA systematic examination works the vehicle in a set order and documents the fuel, electrical, and exhaust systems on their own evidence. Covers exam sequence, photography, and common ignition scenarios. Fatal firesOrigin and cause work continues while the medical examiner and law enforcement run a parallel death investigation. Covers scene coordination, victim documentation, and keeping the two records consistent. CSST and lightningLightning energy on building systems can arc across short gaps and perforate the tubing wall, opening a pressurized fuel line. Covers product identification, bonding verification, perforation preservation, and strike corroboration. Spoliation of evidenceExamination alters evidence, and altered evidence draws sanctions motions. Covers preservation duties, notice to interested parties, and documenting conditions before anything moves. How to write the reportThe step-by-step guide: scene documentation, the scientific method, fire pattern description, determinations stated to a reasonable degree of certainty, and keeping observation separate from opinion. C&O for insurance claimsCarriers, SIU, and subrogation counsel read the report for coverage decisions and cost recovery. Covers what a claims audience needs from the same NFPA 921 report.