Category Archives: FIre Investigation Science

Misuse of Simple Explosion Tools in Complex Explosion Investigations

Scott Davis, Ph.D., P.E., CFEI
Derek Engel, CFEI
Tom DeBold
Peter Hinze, Ph.D., P.E., CFEI
And
Bryant Hendrickson
GexCon US, U.S.A.

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

ABSTRACT

There are numerous simple models that can be used to assist the investigation into fuel-air explosions. These models include simple equilibrium based unvented explosions, single and multiple vent equations for large vessels and rooms, constant flame speed models with completely unconfined and fixed congestion (e.g, TNO Multi-energy model, BST method), TNT equivalent models that compare explosion consequences for gas phase explosions with TNT, etc. Some of these simplified methods can help predict both the free-field blast pressure, as well as the dynamic effects due to the venting of the expanding cloud (e.g., drag forces resulting from the blast wind).

While these models may be appealing to assist in an investigation, extreme caution needs to be exercised when using these models outside their intended application. For example, asymmetries and non-uniform congestion, or partially confined structures can result in simple tools vastly over or under-predicting explosion loads and the associated dynamic effect. This data is oftentimes critical in an accident investigation. This paper will present a variety of case studies where simple tools were incorrectly applied to complex explosion investigations, resulting in incorrect opinions regarding the incident. In contrast, the paper will compare the simplified results with those obtained using more advanced CFD modeling.

Download the Complete Paper Here

Complex Explosion Development in Mines: Case Study – 2010 Upper Big Branch Mine Explosion

Scott David, Ph.D., P.E., CFEI
Derek Engel, CFEI
Kees van Wingerden, Ph.D.
GexCon, US, USA

ABSTRACT
On April 5th, 2010 a methane explosion occurred within the Upper Big Branch mine south of Charleston, WV. Twenty-nine men lost their lives as a result of a flammable concentration of methane that built up in the enclosed space and ignited, resulting in a methane explosion that transitioned into a coal dust explosion. This study used the FLACS CFD solver to conduct a detailed explosion analysis to evaluate the complex overpressure development throughout the mine as a result of the flammable cloud ignition. As a result of the accident investigation, unique explosion patterns were found in the mine where certain “blast indicators” within the mine shafts were deformed in such a manner that was inconsistent with the likely flow of the expanding blast wave. The FLACS analysis will analyze the explosion dynamics and shed light on the damage observations made after the blast.

Download the complete paper here

Matthew E. Benfer, Daniel T. Gottuk
Hughes Associates Inc., USA

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

ABSTRACT

Although significant casualties and damage are attributed to electrical fires, there is still much uncertainty in clearly identifying forensic indicators of electrical components post-fire to be able to justify whether the component damage was a result of the fire (i.e., a fire victim) or whether it signifies a cause. The objective of this study was to assess the damage and potential forensic signatures of a range of electrical receptacle configurations exposed to two types of fires in order to provide a technical basis for realistic electrical fire scenarios, improving fire scene interpretation, and evaluating the utility of forensic analysis techniques. Specifically, the approach was to, first, characterize the damage (e.g., location of damage, melt, arcing, etc.) to receptacle configurations that have been the source of overheating and compare this to data for receptacles exposed to fire. A second objective was to characterize the similarities and differences between arcing and melting in receptacle components and wiring.

Laboratory testing evaluated the impact of a wide range of variables on the formation of overheating connections in residential duplex receptacles. Two types of receptacle configurations have been evaluated: 1) those focused on terminal connections and 2) those focused on plug connections. Testing included 528 receptacle trials, 408 trials with various terminal connections and 120 trials with various plug connections. Thirteen pre-fabricated wall assemblies of 36 receptacles were placed in 8 compartment fire tests and 5 furnace fire tests. The variables evaluated in the fire exposure testing included: the receptacle material, materials of the receptacle faceplate and box, terminal torque, and energized state of the receptacle. A portion of receptacles in the fire exposure testing had overheated connections that were created in the laboratory testing. These receptacles were used to assess whether evidence of overheating would persist after a fire exposure. All receptacles were documented for damage to the receptacle, faceplate, and outlet box including any arcing, overheating, and/or melting.

The results of laboratory testing indicate that only the loosest connections tend to form significant overheated connections irrespective of other variables such as receptacle materials and installation. Characteristics of damage to receptacles as a result of overheating have been identified and have been found to persist even after fire exposure. In addition, locations of arcing within receptacles as a result of fire exposures were identified and characterized. The location of arcing is primarily dependent on the duration and intensity of the fire exposure, as well as the construction and materials of the receptacle, outlet box, and faceplate.

Download the complete paper here

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.

Download the complete paper here

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.

Download the complete paper here

There has been a lot of debate in fire investigation industry recently regarding Arc Mapping.  NAFI’s mission is to increase the knowledge and improve the skills of persons engaged in the investigation and analysis of fires, explosions and arsons, or the litigation that ensues from such investigations. The opinions expressed in this paper do not necessarily reflect the opinion and beliefs of NAFI. Over the next three weeks, we will be sharing different views on Arc Mapping with our members and the industry – it is up to you to draw your own conclusions.

Week 1 – Arc Mapping: New Science or New Myth?
Week 2 – Arc Mapping as a Tool for Fire Investigations
Week 3 – Arc Mapping: A Review of Findings

Abstract
The ATF Laboratory recently issued Special Bulletin No. 2 which offered a series of objections to the arc mapping review presented by this author earlier this year. This paper reviews the original research findings and explains the context of these findings. It then addresses in detail the comments made by ATF, and further addresses the concerns about arc mapping as currently used in the field. It reaffirms that the original findings are correct. It also shows that a new “ellipse” method proposed by the ATF for origin determination from arcing locations is not technically sound.

Download the complete paper here

Analysis of Post-Fire Characteristics of Portable Oil Filled Room Heaters to Determine Pre-Fire Orientation

K. Scott Barnhill, PE
Investigative Forensic Specialists, PLLC

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

ABSTRACT
A portable oil filled room heater is a steel vessel typically with 5 to 8 fins containing approximately 3 to 4 liters of mineral oil. The mineral oil acts as the heat transfer fluid that is heated by an immersed electric heating element. The outward appearance of an oil filled heater is that of an old steam radiator.

An oil filled heater (OFH) exposed to full room involvement conditions will commonly display fire effects to include: rupture of the vessel’s spot welds, localized wavy deformations to the fins in the unwetted regions of the vessel, and differential deformation of the vessel’s fins. This study addresses the post-fire characteristics of oil filled heaters exposed to full room involvement conditions in two burn cells. A primary focus of the study is to determine if the pre-fire orientation of the oil filled heater can be determined by analysis of the post-fire appearance. A description of the dynamics that occur between the wetted and unwetted surfaces when the vessel is exposed to full room involvement conditions is discussed.

Analysis of an OFHs’ post-fire characteristics, to include vessel dimensions and wavy deformations, compared to the burn cell experiment results, allows an investigator to accurately interpret the normal reaction of an OFH to full room involvement as well as to determine its pre-fire orientation (upright or otherwise).

Download the complete paper here

There has been a lot of debate in fire investigation industry recently regarding Arc Mapping.  NAFI’s mission is to increase the knowledge and improve the skills of persons engaged in the investigation and analysis of fires, explosions and arsons, or the litigation that ensues from such investigations. The opinions expressed in this paper do not necessarily reflect the opinion and beliefs of NAFI. Over the next three weeks, we will be sharing different views on Arc Mapping with our members and the industry – it is up to you to draw your own conclusions.

Week 1 – Arc Mapping: New Science or New Myth?
Week 2 – Arc Mapping as a Tool for Fire Investigations

ATF Fire Research Laboratory Technical Bulletin
Arc Mapping as a Tool for Fire Investigations

ABSTRACT
The purpose of this Technical Bulletin is to address statements that are contained in Arc Mapping: New Science or New Myth?, which was presented at the Fire and Materials Conference in February 2017. The paper’s interpretations and analysis of the published literature, the limitations it places on the process of arc mapping, and the conclusion that arc mapping is applicable to less than 1% of fire scene investigations are misleading. This bulletin addresses some of these issues.

Download the entire technical bulletin here.

There has been a lot of debate in fire investigation industry recently regarding Arc Mapping.  NAFI’s mission is to increase the knowledge and improve the skills of persons engaged in the investigation and analysis of fires, explosions and arsons, or the litigation that ensues from such investigations. The opinions expressed in this paper do not necessarily reflect the opinion and beliefs of NAFI. Over the next three weeks, we will be sharing different views on Arc Mapping with our members and the industry – it is up to you to draw your own conclusions.

Week 1 – Arc Mapping: New Science or New Myth?
Week 2 – Arc Mapping as a Tool for Fire Investigations
Week 3 – Arc Mapping: A Review of Findings

Vytenis Babrauskas
Fire Science and Technology Inc., San Diego, CA
Dept. of Mechanical and Aerospace Engineering, University of California San Diego, La Jolla, CA

ABSTRACT
Arc mapping was first introduced in the 2001 edition of NFPA 921 and was subsequently expanded so that in the recent editions it constitutes one of the four main methods for determining the origin of a fire. Careful consideration of engineering principles and large-scale experimental studies on the subject indicates that the relevance and prominence of arc mapping as a leading indicator of fire origin is greatly overstated. The technique is valid and applicable only in some very limited scenarios. Yet it has seen very extensive use in recent years by investigators preparing fire reports. In many cases, such attempted use of arc mapping is based on incorrect and invalid hypotheses, which are often implicitly assumed to be true instead of being explicitly stated. The following are myths: (i) An abundance of arc beads at a given locale means that fire originated in that area, while a paucity of arc beads indicates that it did not. (ii) When multiple arcs are present on a circuit, the direction of arcing will necessarily proceed upstream towards the power source. (iii) If an appliance is the victim of a fire, internal arcing will be primarily near the exterior of the unit, while arcing deep inside indicates a fire origin at that place. NFPA is urged to revise NFPA 921 to eliminate arc mapping as one of the four main methods for establishing fire origin, and to subsume it under the more general category of “fire patterns.” In addition, it is important that NFPA 921 reduce the implied general utility of the method and provide more explicit information on its interpretation and its limitations and on the circumstances under which it may be a valid method for assisting in the determination of the fire origin.

Download the complete paper here

The St. John’s School fire was a deadly fire that occurred on the morning of October 28, 1915, at the St. John’s School on Chestnut Street in the downtown area of Peabody, Massachusetts. Twenty-one girls between the ages of 7 and 17 were burned or crushed to death while attempting to escape the fire.

More than 600 children were in the building when the fire began in the basement of the school building. There were no fire escapes on the outside of the building, but instead those inside were forced to use wide stairways at either end of the interior which led down to the front exit. Mother Superior Aldegon, who led the Sisters who taught in the Catholic school, sounded a fire alarm and began the routine fire drill procedure.

This procedure should have led to the children and teachers leaving the building through the stairways to and out of a rear exit. However, as smoke thickened and the fire came closer, they ran for the front door instead, and became jammed in the vestibule. The fire broke through to the vestibule from directly under the front entrance and the vestibule, now crowded with pupils, was enveloped in flames. The fire rapidly swept through the three-story brick and wooden building, fully engulfing it in less than five minutes.

With their exit blocked, many of the children escaped through first-floor windows or jumped from those on the second and third floors. Not all were able to escape, however; the bodies of the 21 victims were found after the fire subsided, huddled together and burned beyond recognition, on the inside of the school entrance. The Sisters of Notre Dame who taught at St. John’s aided the children trying to escape, some by dropping the students into coats and blankets being used as life nets. These actions were credited in saving many lives. Two of the nuns were injured, one suffering serious burns; however, none of the adults were killed.

As a result of this fire, Peabody became the first city to pass a law that said all doors (in public buildings and school) must push out.

Source: Wikipedia