The accelerating forest fire phenomenon for two real accidents is studied. This phenomenon is investigated using the thermochemical hypothesis, based on the ignition of a biogenic volatile organic compounds cloud accumulated in canyons. By heating a Rosmarinus officinalis plant in a specific hermetic enclosure, a mixture of 14 biogenic volatile organic compounds is identified and their mass fractions determined as temperature functions. The theoretical flammability limits of those components are calculated by means of empirical correlations. Froude-scaling law is applied to laboratory emission results to find the concentrations of biogenic volatile organic compounds at field scale. The comparison of the flammability limits with the calculated concentrations at real scale using this changing-scale analysis shows that the emitted biogenic volatile organic compounds can lead to an accelerating forest fire.

An approach to estimate species production during a compartment fire is proposed. Semi-empirical correlations based on oxygen concentration are given. They give an estimate of the concentrations of carbon monoxide, carbon dioxide, hydrogen, and hydrocarbons with a carbon chain length lower than five. Three intervals of oxygen concentration are noted, and they correspond to sufficiently ventilated, underventilated, and very underventilated fires. In order to validate these correlations, fire experiments are performed in a reduced-scale room. Species concentrations predicted by the model are in good agreement with our experimental data and with those of the literature. Coefficients used in the correlations are obtained for heptane and dodecane fires.