Metallographic analysis and fire dynamics simulation for electrical fire scene reconstruction

This study demonstrated the use of metallographic analysis and NIST's Fire Dynamics Simulator (FDS) program to identify the cause of an actual electrical fire. A severely carbonized steel plate and a cable with a bead were found inside a damaged switchboard from the debris of a factory fire. By metallographic analysis, the copper spatter on the steel plate was found to imply a short circuit has occurred and that this was the probable ignition source of the fire was supported by the presence of a small amount of copper oxide and by the cavities with the tree-like grain microstructures in the bead. The heat estimated to have been released per unit area of the switchboard in question (approximately 236.29 MJ/m(2)) served as key input data for applying the FDS simulation of the blaze. The simulation indicated that thermal insulation polyethylene (PE) played an important role in the rapid fire spread.     

Comparison of new Ampac bags and FireDebrisPAK® bags as packaging for fire debris analysis

Abstract: The FireDebrisPAK^® bags that were produced by Kapak were considered to be one of the best containers for fire debris. Kapak bags were discontinued; however, from July 2010, Ampac is offering a new packaging material. The aim of the presented research was to compare the properties (durability, background interferences, and permeability) of Kapak bags and packaging material offered by Ampac. The analysis was conducted by passive adsorption from the headspace with subsequent thermal desorption and analysis by GC‐MS. The results proved that the properties of the compared materials are similar. Their greatest advantage is that they are impermeable for components of flammable liquids, so there is no danger of losing analytes or cross‐contamination. Their one significant drawback is that they should not be exposed to temperatures above 80°C. At this temperature, they become soft, their inner layer is compromised (becomes sticky), and they emit some volatile organic compounds. Among them, there are compounds that constitute the components of some of flammable liquids.     

论森林火灾现场勘查

森林火灾的现场勘查具有发案时间的季节性、起火部位的特定性、痕迹物证的外延性等特点。森林火灾现场勘查的要点是熟知所辖林区的基本情况;迅速、及时、仔细地勘查现场;确定起火点;弄清案件的性质;作好现场勘查记录。     

Evaluation of Bluestar® Forensic Magnum and Other Traditional Blood Detection Methods on Bloodstained Wood Subjected to a Variety of Burn Conditions,

Accurate blood detection is a primary concern for forensic scientists, especially in highly compromised situations. In this study, blood was added to wood blocks and subjected to a variety of fire treatments: the absence or presence of accelerant, burn time (1, 3, or 5 min), and extinguishment method (smothering or dousing with water). Burned blocks were given a qualitative burn score, followed by removal of half of the char from each block and subsequent testing of each half for blood using luminol (13% positive; n = 96), Bluestar^® Forensic Magnum (5.2% positive; n = 96), and combined phenolphthalein tetramethylbenzidine test (0% positive; n = 192). Luminol and Bluestar® Forensic Magnum performed similarly, both outperforming PTMB. Additionally, positive results were more likely from samples that were smothered, had a low burn score, and had more concentrated blood solutions (neat or 1:2). Overall, it is extremely unlikely that blood would be detected on combustible substrates exposed to direct fire.     

Total Ion Spectra versus Segmented Total Ion Spectra as Preprocessing Tools for Gas Chromatography – Mass Spectrometry Data

Alignment of fire debris data from GC‐MS for chemometric analysis is challenged by highly variable, uncontrolled sample and matrix composition. The total ion spectrum (TIS) obviates the need for alignment but loses all separation information. We introduce the segmented total ion spectrum (STIS), which retains the advantages of TIS while retaining some retention information. We compare the performance of STIS with TIS for the classification of casework fire debris samples. TIS and STIS achieve good model prediction accuracies of 96% and 98%, respectively. Baseline removal improved model prediction accuracies for both TIS and STIS to 97% and 99%, respectively. The importance of maintaining some chromatographic information to aid in deciphering the underlying chemistry of the results and reasons for false positive/negative results was also examined.     

浅议提高消防行政执法的公正性

消防行政执法需要公正。影响消防行政执法公正性的几个因素 ,提高消防行政执法公正性的措施。     

152例火场尸体的法医学检验分析

目的 探讨火场尸体的法医学检验特点及其鉴定。方法 对86起火场中152例尸体的相关检验资料进行回顾性研究。结果 152例火场尸体,生前烧死109例,纵火焚尸38例,无明显高温作用的尸体5例。主要死因有“烧死综合征”100例,火场有毒气体中毒8例,机械性损伤32例(含高坠死4例),机械性窒息5例,电击、服毒各1例;不能确定死因5例。自杀5例,他杀40例,意外107例。在生前烧死尸体,87例呼吸道内有炭末沉着,71例皮肤局部烧伤边缘组织有红肿,46例检见水泡,17例有“闭眼反应”征象,大部分尸体血中HbCO浓度超过20％;纵火焚尸少见或不见上述改变。结论 检验火场尸体,根据烧死尸体征象和血中HbCO浓度检测,并结合火场勘验资料综合分析,其死因鉴定和死亡方式推断结论方能准确。     

Evaluation of Cross‐contamination of Nylon Bags with Heavy‐loaded Gasoline Fire Debris and with Automotive Paint Thinner

Nylon bags are used for packaging fire debris in several countries, particularly in Europe. The possibility of cross‐contamination during transport from the fire scene to the laboratory, in normal casework conditions in the U.K., was studied for two brands of nylon bags, using simulated heavy‐loaded fire debris. Three experiments were carried out with each brand, using as sample a piece of cotton fabric soaked with gasoline. One experiment was carried out using automotive paint thinner (oxygenated solvent). Each sample was sealed in a nylon bag and stored in contact with eight empty bags. The empty bags were analysed at regular intervals for a period of time up to 8 weeks, using SPME and GC/MS. Cross‐contamination was found for components of gasoline (toluene and C₂‐alkylbenzenes) in the two brands of nylon bags used, after 4 days and 2 weeks. Cross‐contamination using automotive topcoat thinner was detected after 2 days.     

Evaluation of Internal Standards for the Analysis of Ignitable Liquids in Fire Debris

Abstract:  An evaluation of eight compounds for use as an internal standard in fire debris analysis was conducted. Tests were conducted on tetrachloroethylene, chlorobenzene, n-octylbenzene, 3-phenyltolune, and deuterated compounds toluene-d8, styrene-d8, naphthalene-d8, and diphenyl-d10 to measure the extraction efficiency of each compound in the presence of an interfering volatile compound (carbon disulfide). Other tests were conducted to evaluate whether or not the presence of an ignitable liquid or pyrolysis/combustion products from fire debris would interfere with the identification of these compounds when used as an internal standard. The results showed that while any of the eight compounds could be used as an internal standard in fire debris analysis, the more volatile compounds (toluene-d8, tetrachloroethylene, chlorobenzene, and styrene-d8) showed better extraction efficiencies at room temperature than when heated to 60°C. Each of the less volatile compounds (naphthalene-d8, diphenyl-d10, n-octylbenzene, and 3-phenyltolune) performed well during extraction at 60°C, while naphthalene-d8 showed better extraction efficiency in the presence of competing volatiles when extracted at room temperature.