Abstract. Cavity walls containing combustible insulation present an increased risk for fire propagation in a confined, concealed space. Damage to the building resulting from ignition of combustible insulation can be extensive; especially so, in the absence of horizontal and vertical fire-stops. Current codes and standards assess fire performance of exterior wall assemblies subjected to external ignition sources. However, test methods do not address the potential fire hazard resulting from ignition of combustible insulation within the wall cavity. A fire performance test has been developed that evaluates the fire propagation behavior of combustible insulation in a configuration that is representative of the actual installation. The test utilizes a full scale cavity wall assembly and offers fire performance evaluation of insulation of any thickness for either a 51 mm or 102 mm wide air space. A propane sand burner was selected as the ignition source; in addition to being reliable and repeatable, its heat output was carefully calibrated to be representative of potential ignition scenarios that may occur within a cavity wall. During the 15 minute fire performance test, the sample is continuously subjected to the propane sand burner exposure fire. An acceptable sample will produce a peak chemical heat release rate less than 100 kW and a maximum visible flame height less than 1.8 m. This fire performance test method is being incorporated into FM Approvals Standard for Cavity Walls and Rainscreens, Class Number 4411 [1] and is suitable for incorporation into other codes and standards.
A simple analytical model is developed for fire growth of thermally-thin corrugated paperboard in a parallel panel configuration that simulates the vertical flues between stored commodities in a rack storage arrangement. It is based on a semi-empirical model for radiation-dominated flame heat transfer to panels in terms of: (1) fuel flame sootiness, (2) fire heat release rates, and (3)
A simple analytical model is developed for fire growth of thermally-thin corrugated paperboard in a parallel panel configuration that simulates the vertical flues between stored commodities in a rack storage arrangement. It is based on a semi-empirical model for radiation-dominated flame heat transfer to panels in terms of: (1) fuel flame sootiness, (2) fire heat release rates, and (3) panel width to separation aspect ratios. The model input properties include: heat of combustion, minimum heat of gasification, yield of smoke, and critical heat flux obtained from the fire propagation apparatus. The effect of moisture on fire growth rate is incorporated in the model. The predictions of the model are compared with experimental data on the rate of chemical heat release measured for the upward fire growth of vertical corrugated paperboard samples (0.305 m × 2.4 m) placed opposite one another in a parallel panel configuration (0.153 m apart). The model predictions of exponential fire growth time constant agree reasonably well with the experimentally determined values. Because of an enhanced role of convective heat transfer for parallel panels with 0.153 m separation distance, an adjustment of radiation constant β 1 was needed for reasonable prediction of fire growth time constant. For a fixed geometry, the model prediction of fire growth time constant depends on the material properties and moisture content.
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