Moisture content can be a dominant factor affecting combustion especially in live fuels due to the wide range of moisture content that can be encountered with vegetation. Laboratory experiments are used to study the fire dynamics of Mediterranean Pinus halepensis needles under a range of fuel and flow conditions. A set of 80 experiments with good repeatability were conducted in the Fire Propagation Apparatus (FPA) fire calorimeter. The burning behavior is measured in terms of the evolution of the mass loss rate and the heat release rate from ignition till burn out for different forced flow velocities. Recently collected live and dead needles are compared here for the first time. Additionally, live samples aged for 15 months after collection are presented as an alternative to study changes in live needles. Two different moisture conditions are considered, fresh and oven-dry. The most flammable samples are fresh dead and 15 months aged needles, followed by oven-dry dead, and oven-dry live needles. The least flammable is fresh live needles. Overall, the results show that fire physics and chemistry vary with the fuel and flow conditions, and that moisture content is not the only difference between live and dead fuels, but that the needle bed physicochemical mechanisms matters as well. The loss of volatiles and other changes induced during oven drying is seen to lead to significant differences in the burning behavior.

SUMMARYLimited research has been conducted on the burning characteristics of live fuels, which are commonly assumed to behave like moist dead fuels. We use small-scale laboratory calorimetric experiments to investigate the differences in fire dynamics between live and dead Pinus halepensis needles. The study includes laboratory-aged samples and different moisture conditions (fresh or oven dry). A series of ten fire behaviour parameters are extracted from the measurements to identify and quantify differences. The main parameters are the following: time to ignition; flaming time; mass loss pre-ignition, during flaming, and during smouldering; peak power; effective heat of combustion; mean and peak CO/CO 2 ; and radiative fraction. Using these parameters, we show that the most flammable samples are fresh dead and aged needles, followed by dry dead and dry live needles. The least flammable is fresh live needles. Live needles ignite about four times slower, and burn with~60% lower power and~50% lower heat of combustion than dead needles. Aged needles resemble most closely the behaviour of dead needles, but many fire behaviour parameters were significantly different. The results confirm the importance of moisture content in the burning behaviour of pine needles, but the differences between live and dead samples cannot be explained solely in terms of moisture but require consideration of plant chemistry and sample drying.

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This paper provides an account of a self-sustaining decomposition event of the NPK (Nitrogen, Phosphorous and Potassium) fertilizer freight aboard the ship Ostedijk. The fire developed inside the cargo hold for several days until it was controlled. Analysis of plume images shows a rapidly growing fire and provides an estimate of the evolution of the mass loss rate, ranging from approximately 0.5 kg•s-1 the first day to 12 kg•s-1 on the last day. Small-scale experiments were conducted to gain an insight into this incident. A three step decomposition mechanism is observed leading to a self-sustained reaction reaching 250-275°C. The measured heat of reaction is 6.1 MJ/kg, about one third of the value for flaming wood. Measurements are applied to the Ostedijk events and allow estimation of the maximum fire size to be in the order of 70 MW. Incidents of this nature challenge the traditional concept of fire, since self-sustaining decomposition events are thermal runaways involving exothermic reactions but not based on oxygen chemistry. However, application of fire engineering concepts and experiments allows the study of the processes.