Incendiary

A type of fire that is intentionally set with the intent to cause damage or harm. Incendiary fires are often associated with arson and require investigation to identify the cause and perpetrator.Under NFPA 921, "incendiary" is one of four fire cause classifications, alongside accidental, natural, and undetermined. A fire is classified as incendiary when the investigation produces evidence that the fire was deliberately set. This is a factual determination based on physical evidence, not a legal one. An investigator can classify a fire as incendiary without identifying who set it or why.Common indicators of an incendiary fire include multiple separate points of origin, the presence of ignitable liquid residues in areas where they would not normally be found, disabled or tampered smoke detectors and suppression systems, removal of personal valuables before the fire, and burn patterns that are inconsistent with the expected fuel load of the structure. Trailers, which are materials arranged to spread fire from one area to another, are another strong indicator.The investigation of a suspected incendiary fire follows the same systematic methodology as any fire investigation. The scene is documented, the area of origin is identified through burn pattern analysis and witness information, and physical evidence is collected for laboratory testing. Samples from areas suspected of containing ignitable liquids are collected in sealed containers and sent to a forensic laboratory for gas chromatography-mass spectrometry (GC-MS) analysis.It is important to distinguish between incendiary and arson. Incendiary is a fire investigation classification describing how the fire started. Arson is a legal term describing a criminal act. A fire can be classified as incendiary without anyone being charged with arson, and arson charges require meeting a legal burden of proof that goes beyond the physical evidence at the scene.Investigators should also be careful not to rely on outdated or debunked indicators. Older training materials sometimes listed crazed glass, pour patterns, and certain char depths as definitive signs of an incendiary fire. NFPA 921 and peer-reviewed research have shown that many of these indicators can also be produced by normal fire behavior and post-flashover conditions. Every conclusion must be supported by the evidence and consistent with the scientific method.For a deeper look at incendiary fires, including case examples and detection methods, see our full guide: What Is an Incendiary Fire? A Comprehensive Guide (https://www.blazestack.com/blog/what-is-an-incendiary-fire-a-comprehensive-guide).