NAFI Blog

Toh Qiu Ping, B.Sc(Mathematical Sciences)
CFEI Singapore Civil Defence Force, Singapore

Tan Kim Haw, M.Sc(HSE), B.Sc(Chem)(Hons)
CFEI Singapore Civil Defence Force, Singapore

Lim Beng Hui, M.Sc(FI)(Dist), B.Eng(Civil)(Hons)
CFEI, CFII Singapore Civil Defence Force, Singapore

Lim Lam Kwang, B.Eng(Mechanical)(Hons)
Singapore Civil Defence Force, Singapore

Anna Teo Li Li, Diploma (Applied Food Science & Nutrition)
Singapore Civil Defence Force, Singapore

Presented at the International Symposium on Fire Investigation Science and Technology, 2018

ABSTRACT

On 27 June 2015, 15 people were killed and more than 500 people were injured in a blaze at the Colour Play Asia event at the Formosa Fun Coast Water Park, just outside Taiwan’s capital, Taipei. The fire was caused by an explosion of a dense cloud of coloured powder – a mixture of corn starch and food colouring – which was sprayed into the air at high velocity over crowds of party goers.

Arising from the incident, there were safety concerns on the use of such coloured powder in other similar events worldwide, including Singapore’s own version of the Colour Run. This paper summarises the fire investigation findings from the tragedy in Taipei, and shares insights on the fire safety assessment conducted by Singapore authorities prior to its own event. Details of a laboratory analysis of the powders used and a hazard evaluation of the event will be presented. The safety measures imposed to minimise the risks involved, for Singapore’s Colour Run and other similar events, will also be discussed.

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Hon. Donald M. Flack(retired)
J.D. Armstrong Teasdale LLP, USA

Presented at the International Symposium on Fire Investigation Science and Technology, 2018

ABSTRACT

Fire and Explosion investigators are often called upon to testify in legal proceedings. For this testimony to be useful, it must explain the relevant scientific principles sufficiently for the audience to understand them, as well as how those principles apply to the facts at issue in the particular case. For the testimony to be useful, or relied upon by the judge or jury, it also must be presented in a way that keeps the audience interested. It can be difficult as an expert witness to control your own testimony because you are limited to responding to the questions being asked. But an expert can greatly improve the effectiveness of testimony with thoughtful planning.

This paper discusses a thoughtful approach to preparing to testify more effectively in four steps. First, consider the audience–whether it is a judge or jury; and if a judge, what type of judge. Second, consider the point of the testimony–what is the conclusion you want the judge or jury to reach? Third, determine which specific scientific principles are necessary to draw the audience to that conclusion–it is important to not skip any steps in the analysis but also to not add unnecessary elements to the discussion. Fourth–consider thoughtfully how to best educate the audience on those principles–for example, use appropriate technical terminology but define the terms and then reduce them to a lay person’s language. Finally, watch the audience and react to them– not only will their expressions and body language provide clues to their level of understanding, but they will notice your attention to them and become even more interested.

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Hubert Biteau, Ph.D., P.E., CFEI
Exponent, Failure Analysis Associates; Atlanta, GA

Nicholas Nava, P.E., CFEI, CVFI
Exponent, Failure Analysis Associates; Bowie, MD

Presented at the International Symposium on Fire Investigation Science and Technology, 2018

ABSTRACT

A tool which is of particular interest in fire and explosion investigations is the modeling of flammable gas concentrations. The use of computational fluid dynamics (CFD) modeling, particularly NIST’s Fire Dynamics Simulator (FDS) is well known in the fire protection engineering community. Considerable research has been performed by engineers and scientists from NIST and within the fire protection engineering community to validate this model.

The use of FDS in modeling gas dispersion for natural gas and propane gas leaks has been the focus of past work by others. Recent interest has surrounded the use of flammable and combustible liquids during cleaning and construction type activities. Flammable gas is produced due to evaporation of the liquid phase. The dispersion of this flammable gas throughout compartments above the Lower Explosive Limit (LEL) can result in a fire or explosion when in contact with a competent ignition source.

The scope of this paper is to demonstrate FDS’s ability to accurately model flammable gas concentration and dispersion. Experimental testing was conducted to determine the evaporation rate of frequently used flammable and combustible liquids. Combustible gas monitors were used to spatially measure the flammable gas concentrations in proximity of a flammable and combustible liquid spill in a controlled diked area. The experiment was then modeled using FDS. Experimental data and modeling results were compared.

This work is of particular interest for those individuals involved in fire investigations who consider using FDS to model flammable gas concentrations. First, results of this experimental work will be presented. Secondly, a comparison of the experimental and model results will demonstrate FDS’s ability to accurately depict flammable gas evaporation and dispersion. Finally, recommendations will be made for the critical input parameters needed to allow for the use of the model for fire origin and cause determinations.

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Yannick Alexis
Daniel Gottuk
Jensen Hughes
Baltimore MD USA
Christopher B. Wood
FireLink LLC
Tewksbury MA USA

Presented at the International Symposium on Fire Investigation Science and Technology, 2018

ABSTRACT

This paper explores thermally induced activation of Molded Case Circuit Breakers (MCCBs) that are commonly found in residential, small office and commercial occupancies. A total of 81 MCCBs were put into an oven with no current (i.e. no-load), along with thermocouples that were connected to a data acquisition system to track trip status and air temperatures proximate to the breakers. Different types of MCCBs were tested and results tabulated based on the brand, number of poles, and amperage ratings of the breakers. All the MCCBs were activated thermally during the testing, and the trip temperatures of the different types of MCCBs are displayed graphically. The breakers tended to trip between 350°F (177°C) and 470°F (243°C) and between 16 to 22 minutes from when the oven reached 160°F (the MCCB’s maximum operating temperature) and then followed a linear temperature increase of 10°F/min (5.6°C/min). The changes in the breakers’ physical conditions were also noted. This experiment provides further evidence that thermal activation of circuit breakers exposed to fire conditions may be a consideration for the investigator of a fire. Recommendations for future work are also included.

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Total Station Surveying Technology for Forensic Mapping of Fire and Explosion Incident Scenes

Brian C. Dunagan, CSP, CFEI, CFII
IFO Group, Inc. – Incident Free Operations, Inc., USA
Christopher F. Schemel, Ph.D.
IFO Group, Inc. – Delta Q Consultants, Inc., USA

ABSTRACT
Total stations (electronic surveying equipment) are frequently used in traffic accident investigations to collect data for reconstruction specialists. For more than 20 years these devices have dramatically reduced the time and labor required to document and map vehicle accident scenes. The data collected by a total station can be easily imported into modeling and sophisticated mapping software. This technology can be deployed in other forensic applications and can be readily used to assist investigators in systematically and accurately mapping fire and explosion incident scenes. This paper summarizes the role a total station plays in forensic mapping. First, an overview of forensic mapping using total stations and associated equipment such as prisms and data collectors is presented. Second, the constraints and the legal considerations of the technology are discussed. Third, a case study using forensic mapping of an explosion scene is presented. Finally, it will be demonstrated that the use of these techniques can assist the savvy investigator in building a compelling case narrative that builds on and complements other evidence collected while satisfying the ever increasing standards for reliable and accurate documentation of scenes.

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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.

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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.

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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.

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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.

Download the complete paper here