On-Scene Characterization of Flammable Liquid Vapors

ON-SCENE CHARACTERIZATION OF FLAMMABLE LIQUID VAPORS USING GC/MS AND SPME SAMPLING

J.D. DeHaan, Ph.D Fire-Ex Forensics Inc. USA
David A. Matthew, M.A. International Association of Fire Chiefs, USA
and
Gareth S. Dobson. Ph.D. Smiths Detection Inc. USA

Presented at International Symposium on Fire Investigation, 2014

ABSTRACT
There has not been a significant advancement in on-scene forensic fire debris analysis in over a decade. The ability to identify an accelerant at the fire scene would provide the fire investigator useful data, increasing efficiency and effectiveness. This research project was intended to establish if the identification of ignitable liquids can be achieved at the fire scene. Three testing sites in Utah, Texas and California provided data that the hand portable Gas Chromatography Mass Spectrometry (GC/MS) with Solid Phase Microextraction (SPME) fiber sampling technique is able to confirm the identity of ignitable liquid vapors at the fire scene consistent with fire debris analysis techniques. Post flashover testing was conducted at three sites in California and one in Utah providing replicable data confirming ignitable liquid vapor identification at low part per billion (ppb) and part per million (ppm) concentrations in real-world fires. The evidentiary samples taken at the testing sites in California were sent to a certified lab to confirm the results from the field data. The GUARDION ® GC/MS produced by Smiths Detection was used for field testing. A limiting factor in the field application of GC/MS was determined when the data produced had to be analyzed by a GC/MS specialist to confirm the identification of the ignitable liquid, similar to current laboratory techniques. It is recommended that a fire debris analysis method be developed to increase the field application of GC/MS.

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A Study of Calcination of Gypsum Wallboard

Christopher L. Mealy
Daniel T. Gottuk
Hughes Associates, Inc.

Presented at International Symposium on Fire Investigation, 2012

ABSTRACT

The prevalence of gypsum wallboard in fire scenes makes it a potentially valuable source of information to fire investigators when assessing a fire scene. The exposure of gypsum wallboard to heat from a fire can result in calcination, which in turn can theoretically be correlated to the total heat exposure to that area. Therefore, if properly characterized, a calcination depth profile of a given enclosure could provide fire investigators with a detailed history of the total heat exposure to the walls and ceiling of the space. This history, when combined with other findings, could provide valuable insight as to where the area of origin was located or how the fire developed. The approach taken in this work incorporated small- and full-scale testing to accomplish several goals: 1) develop an objective method for measuring the calcination depth of gypsum wallboard, 2) assess the utility of the calcination depth surveys in full-scale fires, and 3) characterize the impact of suppression water on calcination depth measurements. In this work a probing pressure of 0.86 kg/mm2  (1175 psi) was identified as providing accurate calcination depth measurements. The benefit of calcination depth surveys in full-scale enclosure fire scenarios was realized primarily for cases where visual patterns were not obvious. The application of water to calcined GWB was found to alter the measured depth of calcination by an average 18 percent, when collected 24 hours after heating/water application and less than five percent after 30 days. This data suggests that if measurements are to be collected in areas that have been wetted by suppression activities for any extended period of time, it would be advisable to delay measurements until the water has been removed.

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Scientific Method-Use, Application, and Gap Analysis for Origin Determination

 

Gregory E. Gorbett, MScFPE, CFEI, IAAI-CFI, CFII, CFPS
Eastern Kentucky University, USA
and
Wayne Chapdelaine, CFEI, IAAI-CFI, CFII
Metro-Rural Fire Forensics

Presented at International Symposium on Fire Investigation, 2014

ABSTRACT
The fire investigation industry is considered to be lagging behind the rest of the forensic science fields in its assessment of the performance of methodological approaches and conclusions drawn by practitioners within the field. Despite the best efforts of certifying bodies and industry members, there are still many unknowns within the profession. This paper will present practical uses of the scientific method as it relates to Origin Determination. Several recommended practices have been identified and formatted to reflect the scientific method as utilized in NFPA 921. In addition, where practical, a gap analysis has been conducted on these processes with recommendations provided.

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Fires Originating in Branch-Circuit NM Cables Due to Installation Damage

Vytenis (Vyto) Babrauskas, Ph.D.
Fire Science and Technology Inc., Issaquah WA

Presented at International Symposium on Fire Investigation, 2014

ABSTRACT
A significant fraction of US structure fires originate in electrical wiring, and there is also reason to believe that these numbers may be systematically undercounted. The role of voltage surges and damaged insulation in creating the potential for fire is discussed. That damaged electrical insulation may lead to fire has been known for a century, yet details of the mechanisms by which this occurs have not been extensively studied. UL recently published a study on damage due to poor workmanship in stapling of cables, specifically cases where the insulation is damaged but the conductors are not split. This study establishes that damage which may not appear visually striking may result in dielectric failure; such failures can be a direct cause of fire. Case histories are presented illustrating how mechanical damage associated with stapling of NM cables can result in serious fires. Two preventive measures are described: (a) installation by use of staplers and not hammers, and (b) testing the dielectric withstand voltage of branch circuits after installation and prior to energizing. Both of these measures, if implemented, should reduce the prevalence of electrical fires. However, given the immense amount of fixed wiring installed in buildings, fires due to damaged insulation do not imply that current wiring methods are a low-reliability technology. Only when serious installation defects are present does fire become a foreseeable event.

Keywords : dielectric strength of cables; electrical fires; forensic failure analysis; electrical installation defects; NM cables; voltage surges.

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Industrial Incident Investigation Techniques

Thomas V. Rodante, P.E., CFEI, CFII
Baker Engineering and Risk Consultants Inc., USA

Presented at International Symposium on Fire Investigation, 2012

ABSTRACT
NFPA 921 provides an excellent framework for individuals charged with the responsibility of investigating fire and explosion incidents. NFPA 921 establishes systematic investigative and analytical scientific techniques around the core principle of scientific methodology. Guidance is provided in NFPA 921 to show and explain the process of evidence collection, analysis, hypotheses formulation, forensic hypotheses testing, hypothesis correction and re-testing, and final cause determination. This presentation provides case study examples, not offered within NFPA 921, of forensic scientific methodology as applied to industrial petrochemical processing incidents.

Specific potential industrial evidence types are discussed and examples provided. The use of a timeline spreadsheet beyond that explained in NFPA 921 is shown with examples of how to correlate process data to witness statements. A case study scenario supposition and hypothesis spreadsheet is provided to show an example method for organizing observations, list related hypotheses, determine forensic test criteria, and document results. The provided example includes scientific forensic use of flame and vapor dispersion modeling, and metallurgical analysis. Finally, an example fault tree is shown as an alternative analytical method for cases in which the existence of physical evidence may be limited.

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ISFI 2016 wrap-up

Last week was ISFI 2016 at the beautiful McCormick Ranch in Scottsdale, Arizona.

We had over 40 presentations on a variety of fire investigation science and technology topics! Thank you to all of our speakers and all of those who submitted high quality papers of their research and experience, we are so grateful for your desire to share and give back to our community. Over 125 delegates joined us from eight countries.

isfi2016_speaker_greg
Gregory Corbett speaking at ISFI 2016

We also want to thank several individuals who contributed time and effort to ISFI 2016 – Gregory Corbett, Ron Hopkins, Vyto Babrauskas, Scott Davis, Wayne Chapdelaine, Kevin Lewis, and Jim Shanley. Without them, ISFI 2016 would have gone on, but it wouldn’t have been nearly as much fun.

 


Deposition Testimony: Don’t Fall Prey to Lawyer Tricks

Karrie J. Clinkinbeard, J.D., CFEI
Armstrong Teasdale LLP
and
Gerald A. King, J.D., CFEI
Armstrong Teasdale LLP

Presented at International Symposium on Fire Investigation, 2014

ABSTRACT
After an expert completes the origin and cause investigation, has carefully reviewed all available data and thoroughly researched the methodology and conclusions, the upcoming deposition should be easy, right? Not if you are unaware of tricks lawyers use to shape the testimony in the manner the adverse lawyer desires. Even the most qualified experts who have followed all elements of the scientific method in formulating their opinions are at risk if they are not sufficiently prepared to handle the opposing lawyer’s tricks. An adverse lawyer’s goal during a deposition is to have the expert say something they did not mean to or say it in a way that harms that party’s case. Lawyers craftily lay a myriad of traps when questioning an expert, especially with experts who are strong advocates for their clients. This article highlights some of the most effective lawyer tricks and provides advice on how to successfully navigate them. The presentation will contain video clips of actual depositions where these lawyer tricks are used, providing real world examples of what to do (and not do) and how to recognize when the adverse lawyer is setting you up.

Download the complete paper here


Emergency Response to Incidents Involving Electric Vehicle Battery Hazards: Full-Scale Testing Results

R. Thomas Long Jr. and Andrew F. Blum
Exponent, Inc., USA

Presented at International Symposium on Fire Investigation, 2014

ABSTRACT
Fires involving cars, trucks, and other highway vehicles are a common concern for emergency responders. Between 2009 and 2011, there was an average of approximately 187,500 highway vehicle fires per year.  Fire Service personnel are accustomed to responding to conventional vehicle (i.e., internal combustion engine [ICE]) fires, and generally receive training on the hazards associated with those vehicles and their subsystems. However, in light of the recent proliferation of electric drive vehicles (EDVs), a key question for emergency responders is, “what is different with EDVs and what tactical adjustments are required when responding to EDV fires?”

The overall goal of this research program was to develop the technical basis for best practices for emergency response procedures for EDV battery incidents, with consideration for suppression methods and agents, personal protective equipment (PPE), and clean-up/overhaul operations. A key component of this project goal was to conduct full-scale fire testing of large format Lithium-ion (Li-ion) batteries as used in EDVs.

This article summarizes the full-scale fire tests performed, reviews the current emergency response tactics, and discusses what, if any, tactical changes relating to emergency response procedures for EDV battery incidents are required.

Download the complete paper here


Today in history: Fire on Saudi jet kills 301

On this day in (August 19) 1980, a fire aboard a plane bound for Saudi Arabia forces an emergency landing.

The Saudi Airlines flight began in Karachi, Pakistan, headed for Jidda, Saudi Arabia, with a stopover in Riyadh. The first leg of the flight was uneventful, and the Lockheed L-1011 took off from Riyadh with no problems. Shortly after takeoff from Riyadh, the pilot reported a fire onboard the plane and told air-traffic controllers that he needed immediate clearance to head back to the airport.

The fire started while passengers onboard were cooking with a portable butane stove. Apparently, this was not unusual, as Middle Eastern airlines are often willing to accommodate their Muslim passengers’ needs to follow the strict dietary laws of their religion. The pilot was able to land the plane back at Riyadh safely and headed to the end of the runway where a rescue crew was waiting.

When the plane reached the end of the runway, however, it burst into flames. The crew sprayed fire-fighting foam at the fire, but it was no match for the intense blaze. None of the 301 people onboard escaped the fire. It is still unclear why there were no survivors. Bodies were found piled up near the escape hatches. One theory is that panic on the plane caused a stampede that prevented the hatches from being opened. Another possibility is that the crew failed to depressurize the cabin, which would have prevented the hatches from opening. It is also possible that everyone on the flight was overcome by fumes before they could save themselves.

Source: History.com


Explosion Severity: Propane versus Natural Gas

Alfonso Ibarreta, Ph.D., PE, CFEI,
Timothy Myers, Ph.D., PE, CFEI, CFI,
James Bucher, Ph.D., CFEI and
Kevin Marr, Ph.D., CFEI
Exponent, USA

Presented at International Symposium on Fire Investigation, 2012

ABSTRACT

Natural gas, composed mainly of methane, is in some ways similar to propane gas. Both fuels have similar energy densities per unit mass, and similar laminar premixed flame burning velocities. However, propane explosions have been shown to produce higher overpressures in unconfined explosion tests when compared to methane. In vapor cloud explosion modeling, methane is considered to be a “low” reactivity fuel, while propane is listed as a “medium” reactivity fuel. In closed vessel explosion testing, the maximum rate of pressure rise for propane is almost twice than that for methane (based on KG  values reported in NFPA 68 (2007) Standard for Explosion Protection by Deflagration Venting , table E.1).

This study provides a direct comparison of the explosion severity between commercial propane and natural gas. Empirical correlations available for vented vessel explosions and unconfined Vapor Cloud Explosions (VCEs) are used to predict the difference in overpressure expected for a commercial propane explosion versus natural gas explosion. Although the maximum laminar burning velocity associated with propane is only about 15% higher than that associated with methane, commercial propane explosions are expected to result in overpressures that are about 40% higher than that of a natural gas explosion under identical conditions with a perfectly-mixed nearstoichiometric fuel-air mixture, based on empirical correlations.

In addition to the laminar burning velocity, other fundamental differences in the fuels may also play an important role in the explosion severity. Propane has a slightly higher expansion ratio than methane when undergoing combustion. The mass diffusivity of propane and methane are also quite different, making the premixed propane flame more prone to wrinkling under turbulent conditions. Future testing in the 20-L explosion chamber is suggested.

Download the complete paper here