Effect of kerosene combustion atmosphere on the mild steel oxide layer

In arson cases, accelerants were usually used by criminals to achieve the purpose of rapid arson. Therefore, fire investigators aim to determine whether accelerants was used in the fire scene. Metallic material has to react with corrosive gas around it at high temperature and the oxidation products may store the information of reactants. Accelerants present in fire scenes impart some oxidative characteristics on metallic materials. The aim of this work is to figure out the possibility to identify the presence of accelerant in a fire according to the oxidation patterns of metallic material. This paper researched the oxidation behavior of mild steel at high temperature in a simulated flame environment. The surface morphological and cross-sectional microstructural features of the samples were characterized by X-ray diffractions, X-ray photoelectron spectroscopy and scanning electron microscopy with energy-dispersive spectroscopy analysis after oxidation. The carbon in the combustion atmosphere had a carburizing effect on the metal oxide layer. It was mostly C–C, C–O and C=O of organic matter could be used as in fire investigation. Various oxidizing atmosphere composite systems promote the formation of metal oxide layers. And bidirectional oxidation mode in the oxide layer further accelerates the oxidation rate. The (wustite) FeO phase was not found in the oxide layer because of the strong oxidation of the combustion atmosphere. These results offer complementary information in fire characteristics, which combining the characterization of surface scale with traditional chemical analysis of recovering ignitable liquid residues from fire debris are expected to offer crucial information for determining the presence of combustion accelerants at a fire scene.

Fire Investigation and Ignitable Liquid Residue Analysis

A fire investigation is a difficult and challenging task. An investigator's basic task at a fire scene is two-fold: first, to ascertain the origin of the fire and, second, to closely investigate the site of origin and try to determine what triggered a fire to start at or near that spot. Usually, an investigation would begin by attempting to obtain a general view of the site and the fire damage; this may be achieved at ground level or from an elevated location. Following this, one may examine the materials available, the fuel load, and the condition of the debris at different locations. Surprisingly, the science of fire investigation is not stagnant, and each year, more information to assist investigators in determining the location and cause of a fire by diligent observation of the scene and laboratory study of fire debris is released. This chapter is split into two sections. The first section discusses the general procedures to be used during a fire investigation, and the second section discusses laboratory analysis of ignitable liquid residue analysis.

Study on the Effect of Jet Direction of Compound Air Curtain on Smoke Control

High temperature smoke caused by fire is a major cause of casualties. In order to ensure the safety of personnel, it is very important to control the spread of smoke and enable personnel to quickly withdraw from the fire scene. While traditional hard isolation, such as fire doors, may hinder the safe evacuation of people, the use of an air curtain as a flexible isolation has received more and more attention from researchers. In this paper, the influence of jet direction of compound air curtain on the smoke control effect was studied, and six working conditions were designed. The temperature and smoke isolation of the compound air curtain were numerically simulated by using ANSYS FLUENT software. The parameters such as temperature, velocity pressure and velocity streamline were analyzed, and the smoke control effects of six different jet directions were discussed. The simulation results were verified by Pyrosim fire simulation software simulation software. The results show that the direction of jet flow has a significant influence on the smoke control effect, and the fire smoke control effect under working conditions 4 and 5 is better. The working condition 5 (both air curtain A and air curtain B have outward jet direction) has the best smoke prevention effect, which is suitable for a situation that is close to the fire source. Working condition 4 (outward direction of air curtain A and inward direction of air curtain B) has the second-best effect of smoke prevention, which is suitable for situations far from the fire source.

Experimental and Modeling Uncertainty Considerations for Determining the First Item Ignited in a Compartment Using a Bayesian Method

Fire scene reconstruction and determining the fire evolution (i.e. item-to-item ignition events) using the post-fire compartment is an extremely difficult task because of the time-integrated nature of the observed damages. Bayesian methods are ideal for making inferences amongst hypotheses given observations and are able to naturally incorporate uncertainties. A Bayesian methodology for determining probabilities to items that may have initiated the fire in a compartment from damage signatures is developed. Exercise of this methodology requires uncertainty quantification of these damage signatures. A simple compartment configuration was used to quantify the uncertainty in damage predictions by Fire Dynamics Simulator (FDS), and a compartment evolution program, JT-risk as compared to experimentally derived damage signatures. Surrogate sensors spaced within the compartment use heat flux data collected over the course of the simulations to inform damage models. Experimental repeatability showed up to 4% uncertainty in damage signatures between replicates . Uncertainties for FDS and JT-risk ranged from 12% up to 32% when compared to experimental damages. Separately, the evolution physics of a simple three fuel package problem with surrogate damage sensors were characterized in a compartment using experimental data, FDS, and JT-risk predictions. An simple ignition model was used for each of the fuel packages. The Bayesian methodology was exercised using the damage signatures collected, cycling through each of the three fuel packages, and combined with the previously quantified uncertainties. Only reconstruction using experimental data was able to confidently predict the true hypothesis from the three scenarios.

Position Optimization with Spectrum Sensing Decision for Unmanned Aerial Vehicles

In the emergency scenario of Unmanned Aerial Vehicle (UAV) relay, link interruption caused by shortage of communication resources often occurs. Using spectrum sensing, UAV can expand communication bandwidth and ensure communication quality. However, spectrum sensing of UAV will increase energy consumption and reduce UAV dwell time. Aiming at the contradiction of energy consumption and communication quality, this paper proposes a relay sensing decision algorithm. Firstly, the spectrum sensing model and algorithm are established. Then, the outage probability is taken as the threshold value adjusting three-dimensional coordinates in the UAV relay sensing decision algorithm. Finally, we construct a UAV relay sensing decision algorithm, which adds the limit of unless outage probability threshold to the firefly algorithm to adjust the position of UAV. By adjusting the three-dimensional coordinates of UAV, the unless outage probability is guaranteed for UAV relay link. Through the simulation of building emergency fire scene, it is verified that the UAV relay sensing decision algorithm can automatically find the optimal UAV sensing position and ensure communication quality.

A Study on Building the Geospatial Data of the Firefighting Area by Applying the 3D Scanning Technology

The acceleration of the economic growth encourages the construction of high-rise and deep-underground buildings, which increase the possibility of the severe loss of life and property in the country in the event of an unexpected large-scale disaster, such as extreme weather. Therefore, recognizing the prior information of the fire scene in event of a fire disaster becomes an important issue for the prompt response; however, the current fire response system has a difficulty in the initial response because proactive collection of the indoor geospatial information on the building is limited in the event of a disaster. As a result, to present the plan for constructing the 3D geospatial data required for the initial response in a fire disaster scene, this study presented the construction case through 3D site scanning and data post-processing using a sample building. This study was conducted to ensure national safety in complex and large indoor spaces with substantial geospatial information of construction in the firefighting area by proposing both the linkage with the intelligent fire forecasting platform and the plan on introducing untact firefighting training as the plan of using the 3D geospatial data.

Numerical studies on an accidental flashfire at a water fun park by FLACS software

A severe accidental fire with ?explosion? resulting from spraying coloured corn flour powder occurred at a water fun park in Taiwan. The possible fire scenarios were studied in this paper using Flame Acceleration Simulator(FLACS). Environmental conditions including wind action and solid boundary conditions were deduced based on government fire investigation and video records, and were used as the input parameters in simulation. Simulation results indicate that upon ignition of the sprayed powder, the maximum overpressure in the open space was only 0.03 bar gauge, with a dust flash fire generated without having an explosion. These environmental conditions or parameters and the simulation results together would give a fire scene that agrees with the accident observed, indicating that appropriate environmental parameters had been identified. Therefore, CFD simulation with carefully selected parameters can be used to reproduce explosion scenarios and to identify key factors in supporting accident investigations.

FIRE INVESTIGATION ACTIVITY MODEL BASED ON A SCENARIO APPROACH

Purpose. Fire investigation is one of the main functions of EMERCOM of Russia. The analysis of activity results of Federal Fire Service forensic institutions based on the current model shows that the point of fire origin is not identified with sufficient accuracy in 63 % of cases, and the fire cause is not unambiguously identified in 74 % of cases. This situation makes it impossible to create an incident information model, to establish cause-and-effect relationships between the phenomena and conditions at a fire scene and also to give the correct legal qualification of the incident. The purpose of the study is to improve the efficiency and effectiveness of fire investigation activities. Methods. The study is based on the theory of system analysis, the theory of functions and the theory of risks. The authors use methods of mathematical modeling and information synthesis, instrumental methods for their support, methods of informatics, expert analysis and combinatorics. Findings. A scenario approach to organize fire investigation activities is proposed. It allows effectively identifying the circumstances of fire occurrence, fire development and negative fire consequences. The problems of the proposed approach are the need to develop a reasonable list of scenarios to be investigated under conditions of information uncertainty and the labour-consuming nature of scenario research, which requires the availability of software and powerful computers. Research application field. The use of the proposed approach will improve the accuracy of determining a fire scenario with severe thermal damage to building structures and interior items caused by fire heat as well as with uneven distribution of fire load in the compartment with the ignition source, taking into account the specific gas exchange in the compartment during a fire and other parameters. Conclusions. The proposed activity model based on the scenario approach, which includes the physical evidence investigation at a fire scene and the results of mathematical modeling of the dynamics of hazardous fire factors, enables to determine the point of fire origin and the cause of the fire and also to establish cause-and-effect relationships between the fire and negative fire consequences with sufficient accuracy.

Hazardous Gas Analysis during Fire Investigation

Various types of hazardous substances are generated at fire scenes. Firefighters usually use the self-contained breathing apparatus (SCBA) during firefighting; however, SCBA is very inconvenient to use in other works (e.g., fire investigation and fire scene commands). Therefore, firefighters can be exposed to numerous chemicals. In this study, concentrations of hazardous gases were measured by utilizing gas analyzers with seven sensors during fire investigations. Six fire investigators measured the concentrations of hazardous gases directly as they worked. This included capturing the maximum concentrations of SO2 at seven places, HCHO at 29 places, NO2 at one place, HCN at 13 places, and CO at two places where the concentration exceeded the short-term exposure limit (STEL). When reconstruction experiments were performed, the maximum allowable concentrations for most hazardous chemicals fell below the STEL approximately 90 min after the fire occurrence. Therefore, we determined that fire investigators should wear proper respiratory protective equipment when working.