Development of a testing protocol for insulation ignition by wildland fire embers
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Wildfire embers, also known as firebrands, are one of the dominant fire spread elements in wildfire growth. These embers are associated with the ignition of structures at the wildland-urban interface (WUI) and there is effort to understand the mechanisms by which they ignite homes. One of the vulnerable areas of homes at the WUI is the attic space. The ignition of attic materials by embers is not a well characterized problem, and so an effort was made to better understand the parameters critical to this issue. This thesis details the assessment of the ignition processes for embers attacking attic materials. An experimental procedure was developed to create consistent embers of specific sizes with well characterized thermal properties. These embers were transferred to various fuel beds, where air flow conditions were adjusted to determine which conditions would cause the fuel bed to ignite, extinguish, or smolder. The materials tested were extruded polystyrene (XPS), expanded polystyrene (EPS), polyurethane (PUR), flame retarded/non-flame retarded denim, and flame retarded/non-flame retarded cellulose, which are all typical insulation materials found in the attic. The differences between flame retarded and non-flame retarded materials were highlighted through these material comparisons. Two configurations of embers, a single large ember vs. an equivalent mass pile of fragmented embers, were tested. Thermocouples and IR camera recordings were used to monitor fuel bed and ember temperatures, in order to investigate the signatures of ignition Once the critical ignition parameter space was defined, a better understanding of the material properties was required to discern what material features were responsible for the ember flammability observations. In order to accomplish this, simple methodologies for measuring thermal conductivity, specific heat, and density were created. The oxygen consumption (cone) calorimeter was used to determine flammability characteristics of the materials, such as heat release rates and ignition times, while thermogravimetric analysis was used to define the material degradation behavior. Finally, X-ray diffraction was explored in order to find the presence of flame retardants in the various materials.