Forest fires are one of the main environmental threats in Chile. Fires in this Mediterranean climate region frequently affect native forests and exotic plantations, including in several cases urban and rural settlements. Considering the scarcity of information regarding the fire response dynamics of tree species that are frequently affected by fires, this study aims to establish a flammability classification according to the evolution of the fire initiation risk presented by the most affected forest species in the Valparaíso region. Three exotic species, Eucalyptus globulus, Pinus radiata, and Acacia dealbata, and two native species, Cryptocarya alba and Quillaja saponaria, were studied. Flammability assays indicate that E. globulus, A. dealbata, and C. alba are extremely flammable, whereas P. radiata and Q. saponaria are flammable. Furthermore, E. globulus and A. dealbata have the highest heating values while Q. saponaria has the lowest values. The extreme flammability of E. globulus, A. dealbata, and C. alba indicates a high susceptibility to ignite. Furthermore, the high heat of combustion of E. globulus and A. dealbata can be associated with a high energy release, increasing the risk of fires spreading. In contrast, Q. saponaria has the lowest predisposition to ignite and capacity to release heat. Accordingly, this work shows that all studied tree species contain organic metabolites that are potentially flammable (sesquiterpenes, aliphatic hydrocarbons, alcohol esters, ketones, diterpenes, and triterpenes) and can be considered as drivers of flammability in vegetation. Finally, these preliminary results will aid in the construction of more resilient landscapes in the near future.

Mediterranean climate regions have become more vulnerable to fire due to the extreme weather conditions and numerous Eucalyptus globulus plantation areas. The aim of this study is to analyze the fire hazard related to E. globulus in a forest fire scenario, based on the contrast of thermochemical parameters and their relationship with chemical properties, considering the predominant exotic forest species (E. globulus, Pinus radiata, Acacia dealbata, and Acacia melanoxylon) present in the Valparaiso region, Chile. The results revealed that although all of the studied species were highly flammable, E. globulus was extremely flammable, as its leaves contain high concentrations of essential oils, monoterpenes, and sesquiterpenes, which can generate a flammable atmosphere due to their low flashpoint and the strong negative influence shown between the essential oils, volatile terpenes, and limonene concentration. Moreover, the heat of combustion of E. globulus was positively correlated with its high essential oil contents. Finally, all of the studied species had low flashpoints and high heating values; therefore, they are predisposed to ignite in the presence of a heat source, releasing high amounts of energy during combustion, which contributes to the risk of the formation and spread of canopy fires among these tree formations.

Background: Fine fuels, characterized by high surface-area-to-volume ratios and rapid moisture exchange, significantly influence fire behavior; yet, cryptogamic organisms, such as lichens, are often overlooked in flammability studies, despite their prevalence in temperate and boreal ecosystems. Lichens, covering ~8% of terrestrial surfaces, can act as ladder fuels, potentially enhancing fire spread in forests. Their flammability is thought to depend on moisture content, chemical composition, and physical traits such as thallus morphology; yet empirical evidence remains limited. This study assessed the flammability of four abundant lichen species from southern Chile, using laboratory epiradiator assays. It evaluated the influence of moisture content, growth form (foliose vs. fruticose), and secondary metabolites on ignition and burning behavior, with implications for fire dynamics under climate change. Results: Moisture content varied widely across species, with foliose lichens generally absorbing more water when hydrated, but fruticose lichens retained slightly more moisture when dry. Ignition frequency was high across all species and humidity conditions (98–100%), comparable to that of native Chilean vascular plants. Ignition and burning times were significantly influenced by moisture content, and to a lesser extent by morphology. In particular, ignition time was significantly longer (1072%) in wet state, while burning time lasted 110% longer in dry conditions. Notably, Nephroma antarcticum retained high flammability even when hydrated, despite longer ignition times, suggesting other traits may offset the dampening effect of water content. Chemical analyses revealed a diverse array of secondary metabolites, particularly terpenoids and phenolics, although their relationship with flammability appeared complex and species-dependent. Conclusions: Despite their poikilohydric nature, lichens ignite readily, acting as effective ladder fuels under both dry and moist conditions, similar to the most flammable species of the surrounding Chilean vegetation. Lichen flammability was primarily driven by its high water-holding capacity, which, similarly to other common forest fuels, influences ignition and burning times, while thallus morphology played a less direct role. Terpenoids may enhance flammability, though N. antarcticum ’s longer ignition times suggest complex interactions. These findings highlight the ecological relevance of lichens in fire-prone ecosystems and underscore the need to integrate them into fire behavior models and management strategies.

Residential wood combustion in energy-vulnerable contexts creates a critical trade-off between thermal comfort and air quality. Conventional emission control technologies often rely on active secondary systems or complex electronic controls that require electricity and maintenance, limiting their adoption in developing regions. This study evaluates a novel stove design integrating Inert Porous Media (IPM) structurally within the combustion chamber to act as a passive primary measure for pollutant reduction. Experimental tests following an adapted EPA Method 5G protocol compared a commercial 11 kW reference stove against an IPM-integrated prototype. Results demonstrate that IPM integration induces thermal reordering that favors secondary air preheating and intensifies heat transfer through enclosure walls. This mechanism increased thermal efficiency by 23% and useful thermal power by 67% while reducing exhaust gas temperatures by 6% and raising external wall temperatures by 18%. Crucially, the prototype achieved a 57% reduction in particulate matter emission rates and a 65% decrease in mass emission factors across the entire granulometric range from TSP to PM1 despite operating at a 15.5% higher burning rate. Normalization by useful energy output revealed systematic reductions of 26% for particulate matter and 33% for carbon monoxide per gigajoule of heat delivered. These findings confirm that structural IPM integration decouples combustion intensification from pollutant formation. The proposed technology offers a scalable and electricity-free solution to reconcile residential heating needs with atmospheric decontamination goals in developing regions.