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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.

Hazards presented by pyrolysis and combustion products during laboratory experiments and real incidents

Crowder, David January 2015 (has links)
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.

Practical assessment of the dependence of fire service intervention times on life safety

Walker, Richard George January 2017 (has links)
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.

Modelling of premixed laminar flame propagating in channels

Li, Fang January 2004 (has links)
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.

Field modelling of flame spread for enclosure fires

Lewis, M. J. January 1998 (has links)
No description available.

Fire Safety for Wildland Homes

Deneke, Fred 08 1900 (has links)
3 pp. / This article gives information about fire protection in rural areas and explains how a homeowner can protect his home. It provides tips for evacuating one's home and defending it.

Fire Safety for Wildland Homes

DeGomez, Tom, Jones, Chris 02 1900 (has links)
Revised; Original Published: 2002 / 4 pp.

Development of fire retardant timber treatments

Lowden, Laura Anne January 2015 (has links)
Fire retardant treated timber has been used in interior and exterior building structures to satisfy the legal flammability requirements. Dricon and NCX are two commercial phosphorus-based products sold by Arch Timber Protection. However, modifications to their formulation may be required due to their boron and formaldehyde contents, respectively. This research aimed to acquire an understanding of the effect of a number of phosphorus-based fire retardants on the decomposition, flammability and burning behaviour of timber, in order to aid their development. Materials have been investigated on a micro-, bench- and intermediate-scale, and evaluated for physical properties. Thermal decomposition has been studied using thermogravimetric analysis in both air and nitrogen, and simultaneous thermal analysis coupled with Fourier transform infrared spectroscopy. Flammability and burning behaviour has been studied using microscale combustion calorimetry and cone calorimetry. Residue analysis has been carried out using scanning electron microscopy coupled with electron dispersive x-ray analysis. Existing fire retardant timber treatments were applied to timber specimens. All three treatments operated in the condensed phase by reducing the onset temperature of timber pyrolysis, and promoting the formation of a stable char and water. Scanning electron microscopy revealed a barrier formation on the surface of Dricon treated char. All treatments increased the CO:CO2 ratio during burning in the cone calorimeter. This is attributed to reduced volatile gas production, enabling simultaneous glowing oxidation of the char surface. Depth of penetration studies showed that high concentrations of phosphorus on the surface of timber is sufficient to significantly reduce the fire growth rate index, but deeper penetration and increased overall phosphorus concentration is more effective at reducing the total heat released by the substrate. New phosphorus-based formulations were applied to timber and their effect on its flammability was assessed. All treatments reduced the total heat released, but not all were effective enough to be used commercially. Ammonium hypophosphite increased the residue yield of timber and was shown to operate via both condensed and gas phase fire retardancy mechanisms. A low melting glass formed a gel-like barrier on the surface of the char, but its melting point was too high to optimise the reduction in peak heat release rate. Both ammonium polyphosphate and guanidine/ammonium phosphate formulations promoted carbonisation of the timber structure. A coherent barrier layer was formed by the organoclay; however, the improvement was not effective enough to warrant further investigation. Combinations of nanometric oxides and phosphoric acid were effective. The oxides catalysed the phosphoric acid mechanism to promote the pyrolysis of timber and re-radiating mechanisms were proposed for the char. Further work is suggested to improve the effect. Layer by layer assembly does not provide a sufficient loading to effectively reduce the flammability of timber. Lastly, attempts were made to address the problems of scale-up between micro scale thermal decomposition, bench-scale burning and intermediate-scale regulatory fire tests. Three models for the prediction of Euroclass results have been compared and applied to the materials investigated within this thesis. A method is proposed for the prediction of the Euroclass of fire retarded timber products. Correlation coefficients between micro-, bench- and intermediate-scale flammability tests have been calculated and the results are discussed.

The thermal response of a pressurised storage vessel and its contents to simulated jet fire impingement

Lacy, Clive B. January 1997 (has links)
The storage of pressure liquefied gas in vessels is subject to various regulations and codes of practice. For example, Liquefied Petroleum Gas (LPG), a commercially relevant product, is subject to Health and Safety Executive Guidelines regarding cylinder/tank arrangements and spacing. In the event of an incident involving fire, the internal pressure and shell temperature of an LPG vessel will rise, and the weakening of steel at elevated temperatures can result in the structural failure of the shell. This can be avoided by the fitting of pressure relief valves, which vent material at a pre-set pressure. However, an ignited release can create a high velocity jet flame which, because of significant radiative and convective components, can generate intense, localised heat loads on neighbouring vessels or pipe-work. However, existing codes of practice have no special provision for the possibility of jet fire incidents. Owing to a lack of detailed information on the thermal response of a LPG vessel exposed to jet flame impingement, a series of laboratory scale tests with simulated, localised jet fire impingement on the exterior shell of a pressure vessel was required. The thermal response and the effects of key parameters, Le. fill level, magnitude of heated zone (Le. size and intensity) and position of simulated impingement, could then be examined for the part-validation of a suitable computer model. In addition, these studies could be used to interpret the results from concurrent full scale jet fire impingement trials. An appropriate pressure vessel was constructed to standard design codes, which incorporated a vent line and dump tank. A suitable LPG substitute was selected. Results from the studies indicated that mixing, and therefore thermal stratification, was highly dependent on the size of the heated zone and its position in relation to the liquid/vapour interface. High Speed Micro-Cinematography was successfully employed to film individual bubble streams within the vessel and to measure individual bubble sizes and velocities for various experimental configurations. Studies were also made on the venting characteristics. Sudden pressure relief caused severe agitation of the liquid phase and the breakdown of thermal stratification. In addition, swelling and aerosol generation through homogenous boiling within the liquid phase was observed. Comparisons with the nodal computer model revealed that the use of only single vapour and liquid nodes was a poor approximation to the detail observed in the small scale studies, where the incident heat flux was relatively low and the simulated region of impingement was highly localised. However, the bulk liquid and vapour temperatures and the pressure response up to the time of venting was generally well predicted. As the degree of engulfment increased the model became a better approximation. Although the full scale trials employed an almost fully engulfing jet flame rather than point source impingement, comparisons have allowed understanding of the liquid and vapour thermal gradients, and the subsequent breakdown of these during venting.

Analysis of the structural response of tall buildings under multifloor and travelling fires

Kotsovinos, Panagiotis January 2013 (has links)
The last decades have seen a surge in the construction of tall buildings all over the world. Due to their, often, innovative and complex layouts, tall buildings can pose unique challenges to architects and engineers. Previous tall building failures raised significant concerns on the applicability of prescriptive fire design for these structures. The use of structural fire engineering can enhance the safety of a tall building under fire by strengthening any vulnerable areas in the structure and at the same time reduce the costs of fire protection by removing it when unnecessary. Commercial finite element and specialist structural fire engineering software have their advantages and disadvantages. In this thesis, the object-oriented and open-source finite element software OpenSees is presented along with its development with structural fire capabilities by the author and other researchers at the University of Edinburgh. Specifically, new pattern, element, section and material classes have been introduced. All the developed code follows the object-oriented paradigm and is consistent with the ethos of the existing framework. Verification and validation studies of the developed code are also presented. Several procedures including that for dynamic analysis of structures in fire for the collapse assessment of structures are discussed. The development of OpenSees with structural fire capabilities allows the collaboration of engineers across geographical boundaries and disciplines using a community tool. In this work, the behaviour of tall buildings under different fire scenarios has been modelled using the developed OpenSees code. Firstly, the collapse mechanisms of generic tall buildings are investigated, namely the strong and weak floor mechanisms are demonstrated, and criteria are established on when each of these mechanisms occurs. The parametric study performed demonstrated that the weak floor collapse is less probable for generic composite buildings however this type of failure can become easier to appear as the number of floors in fire increase. The effect of vertically travelling fires on these mechanisms is also examined. The results of the study show that slower travelling rates delay or avoid the global failure of a tall building compared to quicker travelling rates allowing for the time required for steel members to regain their strength during cooling to ambient temperature. However, it was seen that higher tensile membrane forces were observed in the floors as the travelling rates increased which could result in possible connection failure. Most of the research and design codes, such as Eurocode, typically assume a uniform thermal environment across the floor area of a structure when defining the design fire. However, in reality fires are more likely to travel in large enclosures, hence there is a need to understand how tall buildings behave under more realistic fire conditions such as travelling fires. A methodology for defining the thermal environment of large enclosures using travelling fires has been recently developed at the University of Edinburgh. Taking into account OpenSees' programmable architecture and its recent inclusion with heat transfer capabilities by other researchers, there was a collaborative effort in order to understand the thermal and structural response of a generic composite tall building under horizontally travelling fires. The findings of the study showed that larger travelling fire sizes produce quicker heating to the steel beams while smaller fire sizes produce higher peak temperatures in the concrete slab. The structural analysis also demonstrated that travelling fires produced higher midspan deflections in comparison to Eurocode parametric fires and higher plastic deformations which is an indication of higher damage. Further work focused on looking at the behaviour of tall buildings under the combined scenario of horizontally and vertically travelling fires. The results of the study showed that the travelling fires produce lower maximum compressive and tensile membrane forces in the composite floor compared to the Eurocode parametric fires for the building examined and thus in a multi-floor scenario the columns are pulling-in less after large deflections develop in the floor. More specifically, the short-hot fire produced the most demanding response. This suggests that in long floors where uniform heating is really impossible, the time of failure predicted by parametric fires in a multi-floor scenario can be more onerous. The outcomes of this work can aid designers when considering the structural fire response of tall buildings in a performance based design context. It was demonstrated that multi-floor fires could be a threat for tall buildings, and thus this possibility should be considered in design. The use of more realistic fire definition for large enclosures, such as travelling fires, should also be considered. The travelling fire methodology can provide an enhanced level of confidence for the safety of a building since it can represent a range of similar fires to those that may occur in a real fire scenario.

Radiation model for buoyant flames

Cordero, J. S. January 1993 (has links)
No description available.

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