Emission of biogenic volatile organic compounds involved in eruptive fire: implications for the safety of firefighters

Abstract

Forest fires are can be fatal for firefighters owing to the phenomenon of eruptive fire. The hypothesis of this study is that biogenic volatile organic compounds (BVOCs) accumulate in the vicinity of the fire front. One of the factors required for an eruptive fire to take place is that BVOC concentrations must be between their lower flammable limit and upper flammable limit. When this accumulation of BVOCs is exacerbated by specific geographical zones (e.g. small valleys, thalwegs, canyons), the combination of these two factors can lead to situations with a very high flammability potential, representing a considerable risk for firefighters. In France, 16 firefighters have been fatally injured over the last 15 years. This work was carried out on three species of the Mediterranean basin: Pinus laricio Poir., Pinus pinaster Ait. and Cistus monspeliensis L. The maximum BVOCs emitted as a function of temperature (50–200°C) by these species were 147.9, 11.6 and 56.0 g m–3 respectively. The quantities of BOVCs emitted by P. laricio and C. monspeliensis were sufficiently high for eruptive fires to occur.

Investigation of emissions from heated essential‐oil‐rich fuels at 200 °C

“…In the experiment, the emissions from heated needles or twigs were characterized by high amounts of monoterpenes. The result agrees well with the findings of previous studies . Clearly, these monoterpenes are derived from the essential oil in the fuels.…”

“…Being heavier than air, these unburned flammable gases would possibly accumulate in topographically uneven areas (e.g. canyons or valleys) under no turbulence conditions . Subsequently, the accumulation has potential possibility to lead eruptive fire .…”

“…One of the hypotheses to explain this phenomenon is thermo‐chemical approach, which is based on the possible unburned gas accumulation ahead of the fire . Many scientists believe that the flammable gases emitted by essential oil‐rich fuels before pyrolysis in a fire environment are potential source of the unburned gas . A good proof to support the argument is that the special phenomenon has often been observed in vegetation dominated by dense, essential oil‐rich species .…”

“…Although many previous studies have described and hypothesized the close relationship between essential oil of fuels and fire behavior, little work has been done on the emissions from essential‐oil‐rich fuels before pyrolysis . In contrast, the pyrolysis process has been studied extensively .…”

Great Basin Bristlecone Pine Volatiles as a Climate Change Signal Across Environmental Gradients

“…Terpenes within conifer foliage can increase tree flammability, for example, in lodgepole pine foliage, (E)-β-ocimene and tricyclene shortened time to ignition and lowered temperature at ignition whereas α-pinene, β-pinene, β-myrcene, (E)-β-ocimene, p-cymene, camphene, and tricyclene were each positively correlated with burning rate (Page et al, 2012). Moreover, volatile terpenes emitted from trees have been suggested to alter fire behavior (Barboni et al, 2011;Courty et al, 2012). In our regression analysis, the within-needle terpene emission rates of α-pinene, βpinene, and β-myrcene were significant with elevation or heat load index (Supplementary Table 5), suggesting that at lower and warmer sites these compounds contribute to increased potential flammability, making lower trees more susceptible to wildfires.…”