The burning of two species of pine needles: Pinus halepensis and Pinus pinaster, was studied to characterize the behavior of the forest floor in wildland fires. These fuels are representative of the Mediterranean ecosystem and have very different shapes and surface-to-volume ratios. Calorimetry was performed using the FM-global fire propagation apparatus (FPA). To better understand the effects of transport in the fuel beds, the standard sample holder was replaced by a holder that allowed for the porous properties of the fuel to be studied in a systematic manner. These holders were designed with holes on the surface to allow for different air flow rates to pass through the holder and into the fuel sample. These characteristics created different internal fuel bed conditions and were the first such tests that could be identified that examined transport on this level in these types of wildland fuels. Tests were conducted under natural convection and forced flow. The test series results were analyzed with respect to the direct values of the measured variables and calculated values of heat release rate. Discrete variables of time to ignition, duration of flaming combustion and peak heat release rate were compared using an analysis of variance method. As the experiments were conducted under well-ventilated conditions, the heat release rate calculated by calorimetry was compared to mass loss rate and heat of combustion. CO concentration in time proved to be a good indicator of the combustion dynamics in the fuel bed. Heat release rate, time to ignition and time to reach peak heat release rate indicated a strong dependence on flow conditions and on fuel specie. It was shown that the transport processes in the fuel beds had a significant effect on the burning characteristics.

An experimental approach has been developed to quantify the characteristics and flux of firebrands during a management-scale wildfire in a pine-dominated ecosystem. By characterizing the local fire behavior and measuring the temporal and spatial variation in firebrand collection, the flux of firebrands has been related to the fire behavior for the first time. This linkage is seen as the first step in risk mitigation at the wildland urban interface (WUI). Data analyses allowed the evaluation of firebrand flux with respect to observed fire intensities for this ecosystem. Typical firebrand fluxes of 0.824-1.361 pcs.m -2 .s -1 were observed for fire intensities ranging between 7.35±3.48 MW.m -1 to 12.59±5.87 MW.m -1 . The experimental approach is shown to provide consistent experimental data, with small variations within the firebrand collection area. Particle size distributions show that small particles of area 0.75-5×10 -5 m 2 are the most abundant (0.6-1 pcs.m -2 .s -1 ), with the total flux of particles >5 ×10 -5 m 2 equal to 0.2 to 0.3 pcs.m -2 .s -1 . The experimental method and the data gathered show substantial promise for future investigation and quantification of firebrand generation and consequently a better description of the firebrand risk at the WUI.

A series of experiments of shallow and strong smouldering fronts in boreal peat have been conducted under laboratory conditions to study the CO and CO 2 emissions. Peat samples of 100 mm by 100 mm in cross section and 50 mm in depth were smouldered in the cone calorimeter apparatus. Two laboratory variables, moisture content and the external heat flux are varied over a wide range of values to establish different burning rates and front thicknesses. This provides a novel framework to study smouldering dynamics by varying the controlling mechanisms and providing burning conditions that otherwise cannot be obtained. Measurements of the burning rate and gas flow, yield and ratio for CO and CO 2 are reported at steady state burning conditions. Average mass flow rates per area of smouldering front are reported here for the first time to be 0.27±0.09 g·s -1 ·m -2 for CO and 0.65±0.24 g·s -1 ·m -2 for CO 2 . This CO 2 mass flux is about 3,000 times larger that the natural decomposition flux from peatlands. The CO yield in dry base is 17±3% g·g -1 and the CO 2 yield 42±13% g·g -1 . The CO and CO 2 total yield is of 59±15% g·g -1, and the CO to CO 2 ratio was measured on average 0.43±0.12. The results indicate that peat with high moisture content smoulders producing larger CO 2 yield but the same CO yield compared to dryer peat. This suggests that smouldering of biomass at lower moisture contents develops wider pyrolysis fronts that release a larger fraction of other carbon-containing gas species.