Comparative analysis of extinguishing agents for structural firefighting

Though fire losses have fallen dramatically over the past forty years, fire remains a cause of injury and death in the United States that is of public health significance. The US fire service has advanced in some respects in comparison with pre-modern firefighting, but continues to rely on water with near exclusivity for structural fire extinguishment. While water’s favorable thermal characteristics and ready availability offer good reasons supporting its use, alternative agents such as firefighting foam have been demonstrated to achieve faster and more complete fire suppression with equivalent agent application. A developing body of evidence also points to mechanisms by which alternative agents might inhibit hazardous gas products of combustion such as hydrogen cyanide. A substantial portion of fire injuries result from toxic exposures rather than heat, and reduction of such exposures could have far-reaching impact on fire survival rates. Two common alternative agents, aqueous film-forming foam (AFFF) and compressed air foam systems (CAFS), have achieved a degree of awareness, and attendant performance evaluation, from the fire community. A myriad of other agents, some operating on principles materially different from those of more widely accepted agents, have received little attention, and their potential effectiveness for structural firefighting is largely untested. This literature review attempts to summarize the extant research on various available and proposed extinguishing agents to provide a framework for future assessment of operational, environmental, and life safety considerations of extinguishing agent selection

Fifty Years of Fire Protection Training at Oklahoma State University

Few people besides those in the fire service or in related fields are aware that Oklahoma State University is the home of one of the oldest and most prestigious schools of fire protection in the United States. In the 1930's Oklahoma Agricultural and Mechanical College (as it was then known) began to offer firemanship training through extension program for both paid and unpaid firefighters while its Department of Firemanship Training offered a two-year program leading to an associate degree. Equally important was the publication of fire service training manuals, the now legendary "Oklahoma Redbook" series, begun at the same time. Through leadership in these three areas, the fire protection training program at Oklahoma State University has earned the nickname, "the West Point of the Fire Service." Historically, Oklahoma State University has been a pioneer in the education of firefighters. It was the first college to offer academic credit for fire protection courses and still is one of the few publishers of training materials in the United States. Graduates of the program have established similar schools at other universities and provide leadership in related fields. With the changing times and increasing demands, the program widened its scope to provide fire protection and safety engineering experts first to insurance firms and industry and most recently to the energy field. That so much has been achieved at Oklahoma State University may be laid to several factors: a growing demand for training in fire protection, a favorable academic environment, and a unique cooperation between the city of Stillwater and the university. But the most important factor as this thesis will demonstrate, was the leadership of the program's founders. When that leadership was removed abruptly in the 1960's the program faltered and nearly died. But with some rearrangement a.nd redirection, the program endured and overcame its difficulties so that now, fifty years after its beginning, the fire protection training program at Oklahoma State University deserves and enjoys an international reputation.Histor

Bibliography on aircraft fire hazards and safety. Volume 1: Hazards. Part 1: Key numbers 1 to 817

Ignition temperatures of n-hexane, n-octane, n-decane, JP-6 jet fuel, and aircraft engine oil MIL-7-7808 (0-60-18) were determined in air using heated Pyrex cylinders and Nichrome wires, rods, or tubes. Ignition temperature varied little with fuel-air ratio, but increased as the size of the heat source was decreased. Expressions are given which define the variation of the hot surface ignition temperatures of these combustibles with the radius and the surface area of the heat source. The expressions are applicable to stagnant or low velocity flow conditions (less than 0.2 in./sec.). In addition, the hot gas ignition temperatures of the combustible vapor-air mixtures were determined with jets of hot air. These ignition temperatures also varied little with fuel-air ratio and increased as the diameter of the heat sources was decreased

DEVELOPMENT OF A COUPLED FDS MODELING AND VIDEO ANALYSIS APPROACH TO ESTIMATE THE BURNING CHARACTERISTICS OF A THIN-WALLED HUMANITARIAN SHELTER

Large fires in humanitarian settlements lead to enormous losses in material, time, and resources that organizations allocate toward supporting refugee camps and displaced persons. In the absence of full-scale shelter fire experiments in humanitarian settlements, a combination of video analysis and fire modeling can be used to estimate burning characteristics of the shelter fire. A MATLAB-based image binarization method is developed to measure the flame height and structure loss over the course of fire development in footage from a shelter burn test conducted in Cox’s Bazar, Bangladesh. The conditions of the shelter fire are recreated in Fire Dynamics Simulator (FDS). Diagnostics in the FDS models provide estimates for the flame height, heat release rate, heat flux, and radiant integrated intensity in and around the shelter. The FDS models exhibit a 10-25 second delay in matching key events in the fire development timeline of the original shelter fire. Otherwise, measurements from the FDS simulations show good agreement to measurements from image processing. Based on results from image processing and FDS models, the steady burning HRR is approximately 900 kW for a shelter fire with a flame height range of approximately 4.1-4.5 m

Mitigation of gas and vapour cloud explosions using fine water sprays

For the past fifty years or so, there has been a great deal of interest in the use of water based explosion suppression systems, designed to mitigate or reduce the impact of thermal explosions and their consequential overpressures, which may be as high as 2MPa in outdoor environments. This level of interest has been heightened in more recent years due to a number of high loss explosion events including, Flixborough, UK (1974), Piper Alpha, North Sea (1998) and Buncefield, UK (2005).All of the previous research has focused on the suppression and mitigation proficiency of existing or new water deluge systems, which deploy sprays containing droplets 200≤D32≤1000μm. Where a high speed flame propagates through a region of spray containing such droplets, the flow ahead of the flame will hydrodynamically break up the droplets into fine mist, which in turn will act as a heat sink in the flame, with a resulting degree of suppression. These studies concluded that in most cases, existing deluge systems contributed to a global reduction in flame speed and thus caused a decrease in the resultant damaging overpressures.This present study however, is focused on the mitigation of slow moving deflagrations with resulting speeds of ≤30m/s. A flame travelling at such low relative speeds will not possess the inertia to inflict secondary atomisation by hydrodynamic break up. Consequently, the droplets within the spray must be small enough to extract heat in the short finite moments that the flame and droplets interact (approximately 0.03ms for a representative 1mm thick flame front). Previous theoretical studies have suggested that droplets, D32, in the order of 10μm - 20μm will be required to successfully mitigate combustion without relying on further droplet break up. To date, there have been no other published experimental studies in this area.An innovative high pressure atomiser known as a Spill Return Atomiser (SRA) was selected, which contained a unique swirl chamber and was originally developed for decontamination and disinfection. The efficient atomisation of the SRA produced fine sprays containing droplets, D32, 15μm - 20μm. A series of „cold trials‟ were conducted to further develop the single SRA, which manifested in the creation of several exclusive single and multiple spray options in counter, parallel and cross flow, with the direction of the propagating flame. These new configurations were supplied with deionised water at a liquid pressure of 13MPa and were qualitatively analysed using High Definition (HD) imagery and quantitatively characterised using non-intrusive laser techniques. During the development stages of this study the SRA spray cone angle was increased from 34.7˚ to 49.2˚and the exit orifice flow rate was raised from 0.295 L/min to 1.36 L/min. The increase in flow rate provided a number of spray options ranging from 17≤D32≤29μm, with liquid volume flux of 0.011 cm3/s/cm2 - 0.047cm3/s/cm2 and mean droplet velocity of 0m/s - 21.4m/s, with the resulting characteristics giving way to complete explosion mitigation qualities.The second phase of this study was to conceive, design and build a suitable apparatus capable of producing slow representative flame speeds within the range of 5 m/s - 30m/s. In excess of 250 mitigation „hot trials‟ were performed using the unique conformations produced during the „cold trials‟, whereby a configuration consisting of 4 x SRA‟s in cross flow (X/F) configuration, successfully and repeatedly, completely mitigated homogeneous methane-air mixtures throughout the whole flammable range E.R. 0.5≤(ϕ)1.0≤ 1.69 (5 - 15%), with flame speeds ranging from 5 - 30m/s. The combined spray configuration consisted of four SRA‟s which were 105mm apart and each opposed by 120˚, thus providing a total spray region of 315mm (spray centre to centre). As the sprays did not overlap or converge, the liquid volume flux remained as 0.047cm3/s/cm2.With droplets, D32, ≤30μm generally requiring impact velocities of approximately ≥142.83m/s to break up further, the flame speeds experienced in these trials of ≤30m/s would not have caused hydrodynamic break up of the droplets in the sprays. Therefore, due to the flame speeds and drop sizes utilised in this study, the droplets entering the flame front would have been in their original form.Although some comparisons were made using the experimental data with Computational Fluid Dynamics (CFD), it proved to be an extremely complicated phenomenon. This was due to the presence and interaction of the complexities of the combustion process and other variables such as water droplet dynamics and heat transfer modes. As such, a set of recommendations have therefore been proposed in pursuing this work in future project