The dispersed phase that accompanies enclosure fires, for example, soot, ash, sprinkler droplets and extinguishing powder, could exert a significant influence on the dynamics of the background fluid. In this thesis, the results of a numerical study into the effects of this dispersed phase on the flow in a fire compartment are presented. A two-dimensional computational fluid dynamics solver, with appropriate approximations for low Mach number flows and mathematical sub-models for two­phase flows, has been developed in order to simulate fire induced convective motions in planar compartments. The description of the dispersed particulate is based on a two­continuum approach, whereby the dispersed phase and the gaseous phase are assumed to be two mutually interacting and penetrating continua. In this thesis, two 'passive' models and an 'active' model of the dispersed phase are considered. In the passive models the particulate acts as a tracer only and has no hydrodynamical influence on the gas phase. The second passive model differs from the first in that the production of gases in the fire compartment, for example arising from combustion or propellant gases due to extinguishment of the fire, is taken into account. This second passive model more accurately predicts the growth of pressure in a sealed fire compartment for weak fires. As the volume fraction of the particulate increases the spatial-temporal hydrodynamic influence exerted on the gaseous flow by the dispersed phase becomes significant and, under certain conditions, a passive representation is insufficient. An active one­temperature and one-velocity model is proposed which is appropriate for the description of a hydrodynamically active particulate with an instantaneous velocity and thermal relaxation time. In this thesis, computational fluid dynamics is used as a tool in order to characterise the applicability of the passive models and the active model. The ability of the passive models to accurately predict the growth of pressure in a compartment for 'surface' fires, for example smouldering combustion and weak fires, is investigated. The active model is used to study the hydrodynamics of powder extinguishing media in a compartment with an open doorway.

Heat, flame, smoke and fire gases are responsible for the vast majority of fire deaths and injuries and are all products of the chemical and physical processes that occur within fire. This is well known and supported by fire statistics but current fire safety does not directly consider these factors and the hazard they may pose to life. The aim of this thesis is to bring together knowledge from fire science with evidence from fire investigation to provide a way forward for improving fire safety and protecting life using sound scientific principles. A number of major fires and the associated large scale fire reconstructions carried out as part of their investigation have been analysed to assess the way in which polymeric materials contribute towards the overall hazard and whether there are other factors tending to contribute to the hazard. The Stardust Disco fire highlighted the importance of lining materials in their contribution to both rapid fire development and toxicity. Maysfield Leisure Centre demonstrated the link between functional groups in polymers and the major toxicant likely to then contribute to the developing hazard. Harrow Court showed how a modern incident able to develop to flashover would produce a dramatic change in conditions, capable of overcoming fire fighters as well as civilians. Rosepark Care Home demonstrated the importance of simple fire safety measures such as the closing of doors in keeping products of combustion away from relevant persons. The Lakanal fire highlighted the potential complexity of these sorts of incidents and the way in which they tend to be the result of a large number of “things going wrong” all at once. The fire at Atherstone on Stour revealed the potential for rapid fire development to take place across very large environments, again sufficiently quickly to overcome attending fire fighters. The work carried out has demonstrated the intrinsic link between the burning properties of materials with their toxicity, which are then further influenced by the way in which an environment can influence ventilation conditions, thermal insulation and pathways for fire to spread and impose hazards upon people in relevant areas. Fire safety has developed in such a way that flammability and toxicity no longer appear to be considered together, but the findings from the incident analyses indicate there appears to be a need to bring the subjects of toxicity and general fire safety back together.

This research identifies realistic timelines for human survivability during accidental dwelling fires (ADF). It also establishes a time window within which the fire service is likely to affect a rescue of the occupants from ADFs. Through a comparison of these two timelines, the likelihood that the fire service will rescue an occupant before they receive a fatal dose of heat and/or smoke (asphyxiant gases) is established. The dependence of fire service intervention times is also assessed in the context of increasing intervention times resulting from cuts to fire authority budgets. The results show that an increase in the time taken to affect a rescue will lead to an increase in the number of fatalities and the severity of injuries which occur when the occupants of a dwelling become trapped by (or are otherwise unable to escape from) fire within the property. Around 80% of all fire deaths and injuries in Great Britain occur in dwellings. This study analyses national and local fire statistics to identify the typical fire situations and common circumstances which lead to fire deaths and injuries. This statistical analysis has been used to inform the carrying out of thirteen large-scale fire experiments. Asphyxiant gas concentrations and compartment temperatures were gathered during these experiments, in order to establish human survival times resulting from the adverse effects of exposure to these. Statistics have also been analysed and a methodology developed to establish fire service intervention times. Establishing survival times on the basis of an analysis of national statistics constitutes new work within the field of community fire safety. In addition, the author is in a preferential position to establish realistic times for fire service interventions, and there is no evidence that these timelines have previously been developed to this extent or compared to timelines for occupant survival. The findings of this research should be considered by fire authorities as they make important decisions for the development of local fire service resourcing activities in continuing times of austerity.

The dynamics of the intrinsically unstable premixed flames propagating in channels is studied by means of numerical modelling in this work. Critical conditions of extinction and the influence of the thermal-diffusive effect on the dynamics of flame propagating in planar channels with cold sidewalls under gravity is investigated. For the horizontally propagating flames, the appearance of inversion influences the effect of thermal-diffusion on the asymmetry of flame fronts. For upwards propagating flames, the convex shape of the flame imposed by the mode of ignition combined with buoyancy can suppress the thermal-diffusive effects; in contrast, the buoyancy alone cannot damp the thermal diffusive effects even for quite large Froud numbers in regard to the appearance of inversion. The variation of Lewis number has no essential effect on the planar flame shape formation when flame propagates downward. Lowering Lewis number can significantly decrease the critical conditions of extinction. However, if Lewis number is smaller than some limit, its further effect on the critical extinction conditions is unsignificant. In the two-step consecutive reaction, the effects of the ratio of Damkohler numbers, heat release rates, activation energy and Lewis number on the separation and fragmentation of flames are considered. The inversion is more pronounced in combustion with separated flame fronts than for single-step reactions. However, the inversion is obvious only when the two flame fronts are close enough to each other. Thus, the details of combusiiition chemistry may have a strong effect on the stability of the flame front. The thermal diffusive effect of the first flame is, in certain way, dominant and has influence on the second flame. The presence of the first reaction suppresses the thermal-diffusive effect of the second reaction in regard to the appearance of inversion. The propagation of flames at a variety of Reynolds number ranging from 70 to 1000 are explored. For longer channels or a flat initial flame front, the inversion of the flame is apparent for Reynolds number higher than 200. For large &, the computational grids should be very fine because of the small thickness of preheat zone. The Generalized Curvilinear Coordinate Gridding method is introduced and an elliptic grid generator based on the variational approach is employed to construct the solution-adaptive grids. However, we found out that the global structure of the algorithm required by the adaptive grid approach might be not as efficient as simplified non-adaptive grids for prospective use of massively parallel computers.

No description available.

The purpose of this study was to explore several personal and work-related variables associated with posttraumatic growth (PTG) levels in professional firefighters employed in a large fire district in south Florida. First, the researcher identified common factors in professional firefighting research that were associated with PTG in firefighters (independent variables: perceived supervisor support, occupational stress, coping style, and sense of belongingness). Second, the researcher determined if there was a significant relationship between these independent variables and the dependent variable (PTG). Then the researcher examined whether demographic variables identified from the literature moderated PTG in professional firefighters, such as: number of years of service, trauma history, and military history prior to joining the fire service. The sample consisted of 63 firefighters in a large Fire District in south Florida. The sample size was small and underpowered, and the response rate was low due to the concurrent eruption of the COVID-19 pandemic during the data collection period. Descriptive statistics (means, standard deviations, internal consistency, range, and bivariate correlations) and multiple regression with hierarchical entry were used to test the six proposed hypotheses. The results indicated that perceived supervisor support had a statistically significant relationship with PTG levels in the sample (p = .027). Two of the controlling variables, prior trauma and military history, showed contradictory effects than was indicated in prior research. The present study’s sample reported lower incidences of prior trauma and military history prior to joining the fire service. Clinical implications, ideas for future research, practice, and policy were discussed. / Includes bibliography. / Dissertation (PhD)--Florida Atlantic University, 2021. / FAU Electronic Theses and Dissertations Collection

Grassland organisms evolved alongside the interaction of fire and grazing, but modern management often decouples these disturbances. In order to analyze the effects of reintroducing this interaction, we implemented four treatments. Two of these treatments were variations of patch-burn grazing, one was modified rest-rotation grazing, and one was season-long grazing. We chose to monitor the butterfly response to these treatments because butterflies have short generations, require a wide variety of resources, and are easily identifiable as adults. We quantified both the butterfly community and the behavioral time budgets of two species. We found that the butterfly community is more species-rich and abundant in treatments including fire than in treatments without fire. We found no difference in time budgets between treatments. Overall, we suggest that managers implement a carefully-planned patch-burn grazing regime in order to support grassland butterflies and other organisms.

The assemblage of bacteria and fungi associated with red imported fire ants (RIFA) Solenopsis invicta Buren was obtained from Hinds, Leake, and Madison Counties (location) along Natchez Trace Parkway in Mississippi. The sites were selected due to the limited presence of RIFA within the park and the more natural, undisturbed ecosystem. Active mounds containing soil, plant debris, and RIFA (substrate) were collected in March, July, and November of 2004 (time). Samples were processed according to standard microbiological protocols, and microorganisms identified using morphological, biochemical and molecular methods. A total of 71 bacteria (2324 isolates) and 50 fungi (1445 isolates) were obtained. The most common bacterium and fungus identified were Bacillus sp. B76(B)Ydz-zz, and Trichoderma aureoviride strain IMI 113135. The fungal entomopathogens Paecilomyces lilacinus and Metarhizium anisopliae var. anisopliae were isolated from mound soil, plant debris, and external tissues of the ants. Patterns of species richness, diversity, and evenness values across substrates were 71, 1.58, and 0.37 for bacteria, and 50, 1.11 and 0.28 for fungi, respectively. Total coefficient of community values for bacteria were 0.74 – 0.89 and 0.79 – 0.92 for fungi indicating uniform communities. No consistent trends were observed by comparing substrate, location, and sampling date. However, fungi species richness and diversity for ant external tissues were significantly higher than internal tissues of the ant. Selected bacteria and fungi were evaluated for their biological control and/or antagonistic potential in vitro and in situ. The most promising isolates studied in vitro included Paenibacillus sp. JA-08, Aspergillus terreus, and Aspergillus sp. HZ-35 with death rates on mound soil surface at 4.4, 5.0, and 4.8. The fungus Metarhizium anisopliae var. anisopliae strain LRC 211 had low death rate (1.8) on mound soil during in vitro trial but showed the greatest biocontrol potential during in situ evaluation. After 14 days in situ evaluation, the living RIFA extracted showed sluggish movement and the fungus was recovered from dead (48.3%) and living (33.3%) RIFA. Since the in situ trials were conducted only at one location and season, additional tests, including microscopic documentation of parasitism/pathogenicity, are needed to confirm the results of this study.

One of the major challenges in fire investigation is the determination of the cause of fire. The fire can be accidental or intentional. The determination of ignitable liquid residue (ILR) from fire debris helps the process and this process is called fire debris analysis in forensic science. This is one of the most complex areas in the field of forensics because of the evaporation of the ILR from the debris and the interference of the substrate matrix with the ILR if present. In the present, the final decisions in fire debris analysis are based on categorical statements and it only represents the qualitative but not the quantitative value of the data. The likelihood ratio approach is one of the most widely used methods in forensic science in expressing the evidentiary value. The purpose of this research is to introduce the likelihood ratios calculated by the Naïve Bayes approach. The data for this work was obtained by the Substrate and ILRC Databases from the National Center for Forensic Science. This project also contributed to the expansion of the Substrate Database by adding 1500 new substrate burn data records. The compounds identified from ignitable liquids and substrates were used to calculate the frequency of occurrences of the compounds in substrates and ignitable liquids. The presence or absence of the compounds was determined by the probabilities calculated by logistic regression. These frequencies of occurrences were used in the calculation of Naïve Bayes log likelihood ratios. The application, performance and validation of these models are discussed in this dissertation. These calculated log-likelihood ratios indicated that this method provides high evidentiary values in the classification of fire debris as positive for ILR in most cases but provided low evidentiary values in some other instances.

The current protocols in fire debris analysis rely on ignitable liquid pattern recognition and the identification of target compounds. These practices allow fire debris analysts to determine whether a sample contains or is absent of ignitable liquid residue and to classify that type of ignitable liquid based upon subjective thresholds. A statistical approach using computationally mixed datasets was devised in this research to generate an objective approach to the classification of fire debris samples and to determine error rates. Quadratic, linear, and partial least squares linear discriminant analysis (QDA, LDA, and PLS-DA) models were developed and evaluated to determine the effects of different population distributions and the overall performance on known and unknown ground-truth fire debris samples. The evaluation of the method performance was determined by generating receiver operator characteristic (ROC) curves and calculating an area under the curve (AUC) based on log-likelihood ratios (LLR) scores. The Substrate Database was also expanded within this work to aid fire debris analysts in casework and to provide a more relevant population when generating statistical models. The most optimal population distribution was determined to consist of a uniform population of equal contribution of substrate and ignitable liquids, with each ignitable liquid class represented. The QDA model performed the best when evaluating the cross validation datasets, calculating an AUC of 0.975 ± 0.005. The PLS-DA model calculated the highest AUC for a limited validation 16 known ground-truth dataset (0.991 AUC) in comparison to the other models. All models were evaluated by determining an analyst's threshold for large scale burn data of unknown ground-truth. All models determined a conservative threshold (LLR = 1) as a cutoff score by the informed analyst.