National Association of Fire Investigators

Monthly Archives: August 2017

 
 
FIre Investigation Science

Reduced Scale Enclosure Testing with Low Heat Release Initial Fuel Packages

Mark A. Campbell, CFPS, SET
Wheat Ridge Fire Protection District, USA

Presented at International Symposium on Fire Investigation, 2014

ABSTRACT

The scientific method is the process in which the fire investigator, among other steps, develops a hypothesis and tests it. The 2011 NFPA 921, §20.5.1, states that “Fire testing is a tool that can provide data that compliment data collected at the fire scene (see 4.3.3), or can be used to test hypotheses (see 4.3.6). Such fire testing can range in scope from bench scale testing to full-scale recreation of the entire event.” (bold and italics added). A Full Scale Enclosure (FSE) testing of a hypothesis may be quite expensive, time consuming, and just not practical. Building and burning a Reduced Scale Enclosure (RSE) may provide insight into the various fire effects, patterns, and dynamics within the enclosure.

Previous FSE burns at Eastern Kentucky University examined the results of a low heat release rate initial fuel source and how the area of origin, based upon the fire effects and fire patterns, preserved through post flashover. This paper will discuss current research on the same concept but with the RSE (1/4 scale). Through the use of the applicable scaling laws, low heat release rate initial fuels were designed and applied to various locations on and around the furniture. The RSEs were burned two minutes post flashover. In all four test burns the areas of origin were determined based upon the collective fire effects and fire patterns. These results have demonstrated that the RSE, when applying the scaling laws appropriately, are a very useful tool for fire investigator and fire protection engineers.

Download the complete paper here.

FIre Investigation Science, ISFI Proceedings

Distinguishing Between Arcing and Melting Damage

DISTINGUISHING BETWEEN ARCING AND MELTING DAMAGE IN ELECTRICAL RECEPTACLES

Matthew Benfer and Daniel Gottuk
Hughes Associates Inc., USA

Presented at International Symposium on Fire Investigation, 2014

ABSTRACT

The majority of fire-investigation related literature on electrical arcing focuses on copper wiring, both stranded and solid, with some attention paid to steel (i.e., conduit), and relatively little mention of brass. This is despite the relatively equal presence of copper, steel, and brass in receptacles and similar electrical devices. Changes to NFPA 921 in the 2014 edition of the guide expand upon the characteristic traits which can be used to assess whether arcing or melting is present in a conductor. However, most of the characteristic traits of arcing and melting are qualitative and not well defined in NFPA 921, which leads to more subjective evaluations. In addition, a myopic examination of evidence with respect to the presence of one or two characteristic traits can lead to a false indication of arcing. In cases such as this, other evidence of melting (i.e., in close proximity to the area in question) could preclude confirmation of arcing.

The purpose of this work was to determine which characteristic traits are effective in assessing potential arcing damage on receptacle components and wiring. A total of 86 receptacles were evaluated in this study. Thirty-nine receptacles failed as a result of an overheating connection resulting in arcing damage; this included 95 individual conductors. Forty-seven receptacles with fire-induced arcing were also evaluated; this included 87 individual conductors. All of the evaluated receptacles with fire-induced arcing were energized or energized with a load during testing. In contrast, thirty-seven non-energized receptacles with fire induced melting were evaluated with 57 individual conductors.

The characteristic arcing traits which were evaluated include: corresponding damage on the opposing conductor; localized point of contact with a sharp line of demarcation between undamaged and damaged areas; round, smooth shape; resolidification waves; tooling marks visible outside the area of damage; internal porosity; spatter deposits; and small beads and divots over a limited area. The characteristic traits of melting which were evaluated include: visible effects of gravity; gradual necking of the conductor; and pitting, thinning, and presence of holes in the conductor. These traits were taken from the literature (e.g., NFPA 921) and from observations made during the forensic examinations of receptacles and wiring conducted as part of this work. For each characteristic, there were three possible outcomes: Yes, No, and Possible. Yes indicated that the characteristic was judged to be present on the particular conductor; no indicated that the characteristic was judged not to be present on the conductor. Possible indicated that confirmation could not be made either for or against the presence of the characteristic. All of the evaluations were conducted by the same person.

Corresponding damage on the opposing conductor, localized damage with a sharp line of demarcation, and tooling marks outside of the area of damage were observed on significant portions of arc damaged conductors and small numbers of conductors with melting damage; these characteristics were found to be strong indicators of arcing.

Using multiple characteristic traits and contextual information for determination of arcing vs. fire-melting provides greater confidence in the evaluation of damage. In addition, visual examinations were found to be reliable indicators of both arcing and fire-melting for most conductors. However, there are some cases which would benefit from more advanced examination techniques including SEM/EDS examinations, X-ray, CT scanning (X-ray computed tomography), cross-sectioning and polishing, or other metallurgical methods.

Download the complete paper here.

FIre Investigation Science, ISFI Proceedings

Anatomy of a Wrongful Arson Conviction

ANATOMY OF A WRONGFUL ARSON CONVICTION: SENTINEL EVENT ANALYSIS IN FIRE INVESTIGATION

Paul Bieber, CFEI, B.S., M.L.S. The Arson Research Project

Presented at International Symposium on Fire Investigation, 2014

ABSTRACT

Anatomy of a Wrongful Arson Conviction will discuss the first comprehensive review of U.S. arson exonerations and the first application of sentinel-event and root-cause analysis to the field of fire investigation. Its purpose is to expose and explain the common factors that contribute to wrongful arson convictions.

Sentinel-event analysis has been embraced by several industries as an objective method of identifying and explaining the root causes of errors that have led to harmful outcomes. By reviewing dozens of arson cases, the Arson Research Project has documented the common errors at the heart of many fire investigations where accidental, natural or undetermined fires have been misidentified as arson.

This paper will also highlight the presence and impact of various forms of cognitive bias in each case study and emphasize the importance of objectivity and independence in the reliable application of the scientific method.

The 27 cases being reviewed include 19 exonerations, 7 cases where charges were dropped or a jury returned a not- guilty verdict, and one case that resulted in an execution. Together they represent over 200 years of combined incarceration and several life sentences. Even in the cases where the defendant was acquitted or the charges were dropped, the financial cost and emotional toll to the wrongfully accused were enormous. It is only through a clear examination and better understanding of these common errors that we may hope to avoid similar errors. This case- study review will attempt to shed some light on the problem in an ongoing effort to improve the practice of fire investigation and avoid future wrongful arson convictions.

Download the complete paper here.