Combining heat release rates of combustibles

Many combustibles will be put together in a compartment. If there is a fire, not just one item will burn. In fire hazard assessment, the resultant heat release rate of burning several items, instead of just one single object, has to be known. The principle of superposition is commonly used for combining the heat release rate curves of burning several items. This will be further investigated by carrying out full-scale burning tests. Two combustible items, a polyurethane foam sofa and a timber partition board, were selected. Different combinations were burnt in a full-scale burning facility in the remote area of Northern China. It is found that resultant effects of the transient heat release rate curves of burning two items cannot be obtained simply by adding the individual curves together. The calculated peak heat release rate might be very different from the one determined experimentally if the time to ignition was not considered carefully. However, the curves on the transient total amount of heat released would be similar. Results suggested that the heat transfer between the two items should be considered. In testing single items, including thermal radiation heat fluxes would allow flexibility to combine heat release rate curves of different combustibles together.