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McAllister J.L.,Combustion Science & Engineering, Inc. | Carpenter D.J.,Combustion Science & Engineering, Inc. | Roby R.J.,Combustion Science & Engineering, Inc. | Purser D.,Hartford Environmental Research
Fire Technology

Autopsy and injury data from victims of fire may provide the investigator with important, discriminant, scientific evidence to assist in origin and cause determination. Through the combined use of fire testing, fire modeling, and physiological modeling, the fire investigator may be able to test or further validate their origin and cause hypothesis(es), and other aspects of a fire incident based on the facts of the case and data collected during autopsy or hospital evaluation. As demonstrated in the case study, autopsy data was compared against carbon monoxide concentrations and temperature profiles for two competing origin and cause hypotheses. Only one of the fire scenarios produced toxicant doses and thermal conditions consistent with the victim’s injuries. Hence, the evaluation of autopsy data in combination with the facts of the case and dynamics of the fire assisted in origin and cause determination. © 2013, Springer Science+Business Media New York. Source

McAllister J.L.,Combustion Engineering Inc | Roby R.J.,Combustion Engineering Inc | Levine B.,State of Maryland | Purser D.,Hartford Environmental Research
Forensic Science International

Assigning a level of significance to cyanide concentrations found in the blood of fire victims is often hampered by the fact that cyanide is inherently unstable in cadavers and in stored blood samples. A few researchers have proposed that sodium fluoride can be used to minimize the instability of cyanide in blood samples; however, controlled studies have not been performed to support validation of this hypothesis. To test the sodium fluoride hypothesis, both treated and control blood samples from 14 autopsied fire victims were tested over a 25-30 day period. A 2% concentration of sodium fluoride was added to the blood samples at the start of testing and the samples were refrigerated between testing intervals. Cyanide concentrations in the treated and control samples were measured between 9 and 11 days post treatment and between 25 and 30 days post treatment. A statistically significant difference was not present between blood cyanide concentrations in treated and control samples between 9 and 11 days. During this time period, although there were small statistically significant increases in both treated and untreated samples the fluctuations were minor. Since the treated and control samples did not exhibit instability between 9 and 11 days, it is not surprising that the sodium fluoride appeared to have no effect. However, a statistically significant difference between blood cyanide concentrations in treated and control samples was observed between 25 and 30 days. Those samples treated with sodium fluoride showed a reduction in blood cyanide variability with virtually no overall change, over a 25-30 day period when compared to control samples, while unconditioned samples showed a significant, average increase of 35%.Based on the findings of this study, it is recommended that 2% sodium fluoride be added to blood samples obtained from fire victims to reduce cyanide instability due to bacteriological activity. © 2010 Elsevier Ireland Ltd. Source

Boyce K.E.,University of Ulster | Purser D.A.,Hartford Environmental Research | Shields T.J.,University of Ulster
Fire and Materials

The quantification of merging flows and the factors that influence evacuee merging behaviour are important considerations in our understanding of emergency evacuation of particularly high-rise buildings, and essential for better escape route design and evacuation modelling. This paper presents the results of three evacuation studies to investigate merging flows and behaviours on stairs. Stair:floor merging ratios are provided together with specific flows from the floor and stair. The potential influence of the geometrical location of the floor relative to the stair and the occupant population is discussed. The results indicate that, despite differences in the geometrical location of the door in relation to the stair and the relative stair/door width, the merging was approximately 50:50 across the duration of the merge period in each of the buildings studied. Differences in merge patterns were however evident throughout the merge periods in each of the buildings, particularly in the case where the floor occupants approached from a corridor adjacent to the incoming stair, in which case floor occupants took priority during periods of slower movement. There were also suggestions that some occupant characteristics such as gender or role may have a potential influence on merging, with very obvious deference behaviour of a few individuals dictating the merging in a mixed occupancy building. The studies highlight the potential influence of geometrical location of floor relative to the stair, relative door/stair widths and population characteristics on merge patterns and indicate that much more work is required in this area. Copyright © 2011 John Wiley & Sons, Ltd. Source

Gwynne S.M.V.,Hughes Associates, Inc. | Gwynne S.M.V.,University of Greenwich | Purser D.A.,Hartford Environmental Research | Boswell D.L.,Hughes Associates, Inc. | Sekizawa A.,Tokyo University of Science
Journal of Fire Protection Engineering

In this article, the staff pre-warning delay concept is developed: the time between staff becoming aware of an incident by receiving a pre-alarm, or as a result of other cues, and the raising of a general alarm. This represents the potential delay in staff response as they interpret the cues received and engage in various response behaviors before warning the population and raising a general alarm; a delay that may be procedural and/or cognitive. The theoretical basis for this concept is discussed, examples of incidents involving this delay described and data from experiments and incidents examined to help demonstrate and estimate the impact and the effects upon the available safe escape time/required safe escape time calculation. Hypothetical examples of how pre-warning delay can influence required safe escape time are presented, along with a discussion of the aspects of emergency procedures that are particularly susceptible to this type of delay. A framework for understanding these susceptibilities is suggested, together with proposals for dealing with this aspect in engineering designs so as to evaluate and minimize its impact on escape time. This concept is considered important as the exclusion of a (potentially sizable) delay from the engineering design may lead to artificially optimistic results being produced. © The Author(s) 2012 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav. Source

Purser D.,Hartford Environmental Research
Polymer Degradation and Stability

Fractional Effective Dose (FED) calculation models for incapacitation and lethality are based upon a concept that overall toxicity results from the effects of a few key toxic gases and that the interactions between the component gases are essentially additive (with a possible multiplicative [synergistic] effect of CO 2). A body of experimental data exists for common polymeric materials for lethal toxicity in rats (30 min LC 50 + 14 days post exposure observation) combining animal data with chemical test atmosphere analysis. This data set has been used to compare LC 50 concentrations calculated using two multi-gas FED models, the Levin N-Gas model and the Purser rat LC 50 model, with the measured animal LC 50 results. The Purser rat LC 50 model has then been used to calculate LC 50 concentrations for a range of common materials decomposed under conditions considered typical of four types of compartment fires as specified in ISO 19706: non-flaming oxidative, well-ventilated flaming, under-ventilated flaming and post-flashover under-ventilated flaming. It is concluded that both FED models give reasonably good predictions of overall toxicity for flaming fires, while the Purser LC 50 model, which includes a term for the toxicity of organic irritants, provides a good fit for both flaming and non-flaming decomposition effluent toxicities. The results therefore confirm that for a range of common polymers, toxicity can be predicted in terms of the additive effects of a small number of key toxic gases, especially for flaming fires, while the generalized mix of organic compounds make a contribution to the toxicity mainly under non-flaming conditions, in which they form a significant proportion of the overall effluent mixture. © 2012 Elsevier Ltd. All rights reserved. Source

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