Monthly Archives: December 2017

Observations on Two Fires in Which the Spill of Flammable Liquids Led to Deflagration and/or Flash Fire in a Stratified Heavy Vapor/Air Mixture

Giovanni Cocchi, P.E., Ph.D.
ARSON Fire, Safety and Environmental Investigations S.r.l., Italy

Presented at the International Symposium on Fire Investigation Science and Technology, 2014

ABSTRACT

The most common kind of diffuse phase explosions investigated by fire investigators involve methane or LPG, either accidentally or willingly allowed to accumulate in the confined volume of the room(s) of a building. Many volatile ignitable liquids can form a flammable vapor/air mixture when spilled on the floor and let evaporate for enough time. Upon ignition, flash fire or deflagration will take place, possibly followed by the development of a compartment fire. This work reviews the relevant literature about evaporation of volatile ignitable liquids, heavy gas dispersion and propagation of flame front in stratified heavy vapor/air mixtures. Subsequently, two cases in which the author was asked to provide its technical opinions will be discussed. The first one is a massive semi-confined deflagration in a large storage room that eventually vented through the weakest brick wall of the building. The building was not equipped with natural gas lines and no LPG can was retrieved at the scene. Subsequent fire debris analysis demonstrated the use of volatile accelerants. The second one is a flash fire that was caught on CCTV camera. Around four minutes before, a person was taped while pouring a liquid…After the flash fire, the puddles of liquid of what was intended to be a trailer were observed to burn as pool fires, until smoke obscured the camera. The flame front of the flash fire shows all the relevant features that other authors have previously shown to be peculiars of flash fires in a stratified heavy vapor/air mixture. Fire investigator should consider that when an explosion or a flash fire take place before fire development and natural gas or LPG sources can be legitimately ruled out, use of highly volatile accelerants should be regarded as a legitimate hypothesis and tested according to the scientific method of NFPA 921-2014 .

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Measuring the Impact of Cognitive Bias in Fire Investigation

Paul Bieber, CFEI, B.S., M.L.S.
Director of the Arson Research Project, USA

Presented at the International Symposium on Fire Investigation Science and Technology, 2012

ABSTRACT

Cognitive bias has been found to shape decision making in a wide variety of fields. Criminal investigation and the forensic sciences are no exception.  Fire investigation, part criminal investigation, part forensic examination, is uniquely positioned to be influenced by the affects of cognitive bias.

The 2009 report from the National Academy of Science, Strengthening Forensic Science in the United States; A Path Forward (NAS Report) , recognizes conceptual bias as a factor in all forensic disciplines.  The National Fire Protection Association Guide for Fire and Explosion Investigation (NFPA 921)  acknowledges these biases as a concern in fire investigation.3

This report will explore the most common forms of cognitive bias found in the field of fire investigation, review past research and give recommendations on how these biases might be minimized. It will also present the results of new research which sought to measure the influence of expectation and role bias in fire investigation. A companion report, “Case Study Review of Contextual Bias in Fire Investigation” is available at www.Thearsonproject.org.

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The Differences Between the North American Building Constructions and the Southern European Building Constructions Affects the Type of Fire Pattern That Are Most Commonly Found in a Fire Scene

Giovanni Cocchi, P.E., Ph. D.
ARSON Fire, Safety, and Environmental Investigations S.r.l., Italy

Presented at the International Symposium on Fire Investigation Science and Technology, 2014

ABSTRACT

Fire pattern analysis is a fundamental step in any fire investigation, since it provide the basis for the heat and flame vector analysis onto which the reconstruction of fire spread and the identification of the area of origin of the fire are based. Fire patterns formation depends on the fire effects being produced by the fire. This works discuss some of the differences between building construction in North America and Southern Europe, on the basis of the example of Italy, and try to tackle the problem if such differences may affects the type of fire patterns that are found in a fire scene.

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