|Title:||A critical analysis on the fire safety aspects of furniture|
|Subject:||Hong Kong Polytechnic University -- Dissertations.|
Furniture -- Fire testing.
|Department:||Department of Building Services Engineering|
|Pages:||xviii, 133,  leaves : ill. ; 31 cm.|
|Abstract:||Consequent to several big fires in Hong Kong, local citizens are more concerned about furniture fires. Local government has started to review this issue seriously. As furniture plays a prominent role in fatal fire scenarios, a detailed investigation of the probable hazards due to furniture fires is necessary. The objective of this thesis is to carry out an in-depth study on the fire safety aspects of furniture. General aspects of furniture fires were reviewed first. The relevant regulations, standards and other investigations on the fire safety aspects of furniture were then reported. Key aspects such as thermal properties of materials, smoke production, toxic potency, fire retardant and the effects on and due to the burning environment were considered. Experiments should be carried out to study the fire behaviour of common furniture and their constituent materials. Local furnitures were studied by bench-scale experiments with a cone calorimeter and full-scale burning tests through a room calorimeter in China. Typical furniture and materials including wood, foam, cloth and plastic materials commonly used were tested under different fire conditions. Key parameters such as the heat release rate, smoke release rate, productions of carbon monoxide and carbon dioxide by burning those samples were measured. The possibility of onsetting flashover in a room fire and smoke toxicity were analyzed. Heat release rate was identified as the most important parameter in the literature. Available equations with the oxygen consumption method were further reviewed. A general equation for calculating heat release rate with its simplified versions was derived. Corrections for incomplete combustion under different environments and with fire suppression were discussed. Superposition of the heat release rate curves of individual furniture components was proposed to give the overall results. These were demonstrated by bench-scale and full-scale burning tests. Comparison was made by functional analysis. Predicted curves agree better for tests under higher heat fluxes. Burning furniture in a room might onset flashover. As observed from full-scale and bench-scale tests in this study, burning furnitures (not yet ignited) under a flashover fire would give very different pictures. Firstly, the heat release rate is much higher than that in burning only part of the combustibles in a small accidental fire before flashover. Secondly, toxicity of smoke will be very different. Therefore, furniture is suggested to be tested in a well-developed fire. Smoke toxicity of burning furniture is another important aspect in fire safety assessment. The calculation procedure for estimating the lethal toxic potency and fractional effective dose in burning combustibles with a cone calorimeter was clarified. The toxic gases yields other than their concentrations measured in a cone calorimeter should be considered to avoid confusion. Toxic gases are supposed to be dispersed into a specific total air volume. The cone calorimeter is further demonstrated to be a suitable bench-scale facility to assess the smoke toxicity if a correct calculation method is used under appropriate testing conditions. A fire risk ranking system with three parameters on flashover propensity, total heat released and smoke toxicity through lethal toxic potency is proposed based on the above study. Potential hazards of different furniture materials can then be specified. The ranking system will be useful for the authorities to set up relevant regulations on controlling the furniture materials. Lastly, a fire zone model was developed for predicting the fire environment in burning furniture. Thermal radiation of smoke plays a very important role in real room fires and the key properties were reviewed. The zonal method through a non-gray particulate radiation model was applied to upgrade the fire zone model on studying transition to flashover. Effect of vent opening, particulate volume fraction and the external heat transfer coefficient on the transient temperature rise and onsetting flashover were studied. Both the external heat transfer coefficient and the particulate volume fraction are shown to be parameters which can lead to thermal instability, onsetting flashover in a room fire. The size of the vent opening also has a significant effect on the hot layer temperature and wall temperature.|
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