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Fire Hazard (fire + hazard)
Selected AbstractsSelf-Propagating Domino-like Reactions in Oxidized GraphiteADVANCED FUNCTIONAL MATERIALS, Issue 17 2010Franklin Kim Abstract Graphite oxide (GO) has received extensive interest as a precursor for the bulk production of graphene-based materials. Here, the highly energetic nature of GO, noted from the self-propagating thermal deoxygenating reaction observed in solid state, is explored. Although the resulting graphene product is quite stable against combustion even in a natural gas flame, its thermal stability is significantly reduced when contaminated with potassium salt by-products left from GO synthesis. In particular, the contaminated GO becomes highly flammable. A gentle touch with a hot soldering iron can trigger violent, catastrophic, total combustion of such GO films, which poses a serious fire hazard. This highlights the need for efficient sample purification methods. Typically, purification of GO is hindered by its tendency to gelate as the pH value increases during rinsing. A two-step, acid,acetone washing procedure is found to be effective for suppressing gelation and thus facilitating purification. Salt-induced flammability is alarming for the fire safety of large-scale manufacturing, processing, and storage of GO materials. However, the energy released from the deoxygenation of GO can also be harnessed to drive new reactions for creating graphene-based hybrid materials. Through such domino-like reactions, graphene sheets decorated with metal and metal oxide particles are synthesized using GO as the in situ power source. Enhanced electrochemical capacitance is observed for graphene sheets loaded with RuO2 nanoparticles. [source] Self-Propagating Domino-like Reactions in Oxidized GraphiteADVANCED FUNCTIONAL MATERIALS, Issue 17 2010Franklin Kim Abstract Graphite oxide (GO) has received extensive interest as a precursor for the bulk production of graphene-based materials. Here, the highly energetic nature of GO, noted from the self-propagating thermal deoxygenating reaction observed in solid state, is explored. Although the resulting graphene product is quite stable against combustion even in a natural gas flame, its thermal stability is significantly reduced when contaminated with potassium salt by-products left from GO synthesis. In particular, the contaminated GO becomes highly flammable. A gentle touch with a hot soldering iron can trigger violent, catastrophic, total combustion of such GO films, which poses a serious fire hazard. This highlights the need for efficient sample purification methods. Typically, purification of GO is hindered by its tendency to gelate as the pH value increases during rinsing. A two-step, acid,acetone washing procedure is found to be effective for suppressing gelation and thus facilitating purification. Salt-induced flammability is alarming for the fire safety of large-scale manufacturing, processing, and storage of GO materials. However, the energy released from the deoxygenation of GO can also be harnessed to drive new reactions for creating graphene-based hybrid materials. Through such domino-like reactions, graphene sheets decorated with metal and metal oxide particles are synthesized using GO as the in situ power source. Enhanced electrochemical capacitance is observed for graphene sheets loaded with RuO2 nanoparticles. [source] Fire hazard evaluation of thermoplastics based on analytic hierarchy process (AHP) methodFIRE AND MATERIALS, Issue 5 2010Baogang Yu Abstract Combustibility performance of 14 compositions including five main thermoplastics (polycarbonate (PC), polypropylene (PP), high impact polystyrene (HIPS), acrylonitrile butadiene styrene (ABS) and poly (vinyl chloride) (PVC)) was tested by cone calorimeter. The fire growth index, total heat release amount index, total smoke release amount index and toxicity product index were calculated, based on which an index system for evaluating fire hazard was set up. All factors in this index system had been analyzed by the analytic hierarchy process, and the specific weight for each factor had been determined. Then fire hazard of thermoplastics was evaluated considering integrated fire hazard index. The results show that fire hazards of HIPS-phosphate fire retardant (PFR), PVC-non-flame retardant, ABS-brominated flame retardant (BFR) and PC/ABS-PFR are higher than PC-BFR and PP-non-halogenated flame retardant. Copyright © 2009 John Wiley & Sons, Ltd. [source] Evaluation of the effectiveness of an early peripheral burning strategy in controlling wild fires in north-western ZimbabweAFRICAN JOURNAL OF ECOLOGY, Issue 4 2009Isaac Mapaure Abstract A review of the occurrence of wild fires in Sengwa Wildlife Research Area (SWRA), Zimbabwe, is presented for the period 1965,1993. The effectiveness and desirability of early burning of peripheral areas introduced in 1979 are evaluated. More than 75% of wild fires occurred between July and October, 48.6% of which originated from communal lands. Early burning of peripheral areas led to significant reductions in extent of areas burnt, from annual mean areas of 115 km2 (1965,1978) to 11 km2 (1979,1993) because of effective control of fires, which originated from communal lands. Some areas did not burn at all after 1979, and the overall probability of burning dropped from 0.484 to 0.187. Whilst it may be desirable to keep fires out of SWRA in the short term, fuel build-ups increase the fire hazard resulting in negative consequences on biodiversity in the long term. Consideration should be given to combine peripheral burning with low-intensity prescribed burning of selected blocks to keep a semblance of natural fire regimes to ensure the maintenance of biodiversity while simultaneously reducing the fire-hazard. An integrated fire management plan should be put in place for SWRA. Résumé Ici est passée en revue l'occurrence de feux sauvages dans l'Aire de recherche sur la faune sauvage de Sengwa (SWRA), au Zimbabwe, pour la période 1965,1993. L'efficacité et l'opportunité des feux précoces des zones périphériques, introduits en 1979, sont aussi évaluées. Plus de 75% des feux sauvages avaient lieu entre juillet et octobre, dont 48,6% trouvaient leur origine dans des terres communales. Le brûlage précoce des zones périphériques a conduit à des réductions significatives des superficies brûlées, qui sont passées d'une moyenne annuelle de 115 km2 (1965,1978) à 11 km2 (1979,1993) grâce au contrôle efficace des feux qui commençaient dans les terres communales. Certaines zones n'avaient pas brûlé du tout depuis 1979, et la probabilité globale de brûler a chuté de 0,484 à 0,187. S'il est, à court terme, souhaitable de préserver la SWRA contre les feux, l'accumulation de matières combustibles augmente les risques de feux qui pourraient avoir, à long terme, des conséquences négatives sur la biodiversité. Il faudrait envisager de combiner les feux en périphérie avec des feux programmés, de faible intensité, de certains blocs sélectionnés, pour conserver un semblant de régime naturel de feux et ainsi garantir le maintien de la biodiversité tout en réduisant les risques de feux. Il faudrait instaurer un plan de gestion des feux pour la SWRA. [source] Understory vegetation response to mechanical mastication and other fuels treatments in a ponderosa pine forestAPPLIED VEGETATION SCIENCE, Issue 2 2010Jeffrey M. Kane Abstract Questions: What influence does mechanical mastication and other fuel treatments have on: (1) canopy and forest floor response variables that influence understory plant development; (2) initial understory vegetation cover, diversity, and composition; and (3) shrub and non-native species density in a second-growth ponderosa pine forest. Location: Challenge Experimental Forest, northern Sierra Nevada, California, USA. Methods: We compared the effects of mastication only, mastication with supplemental treatments (tilling and prescribed fire), hand removal, and a control on initial understory vegetation response using a randomized complete block experimental design. Each block (n=4) contained all five treatments and understory vegetation was surveyed within 0.04-ha plots for each treatment. Results: While mastication alone and hand removal dramatically reduced the midstory vegetation, these treatments had little effect on understory richness compared with control. Prescribed fire after mastication increased native species richness by 150% (+6.0 species m2) compared with control. However, this also increased non-native species richness (+0.8 species m2) and shrub seedling density (+24.7 stems m2). Mastication followed by tilling resulted in increased non-native forb density (+0.7 stems m2). Conclusions: Mechanical mastication and hand removal treatments aided in reducing midstory fuels but did not increase understory plant diversity. The subsequent treatment of prescribed burning not only further reduced fire hazard, but also exposed mineral soil, which likely promoted native plant diversity. Some potential drawbacks to this treatment include an increase of non-native species and stimulation of shrub seed germination, which could alter ecosystem functions and compromise fire hazard reduction in the long-term. [source] Changes in heathland vegetation under goat grazing: effects of breed and stocking rateAPPLIED VEGETATION SCIENCE, Issue 1 2010Rafael Celaya Abstract Questions: How are heathland vegetation dynamics affected by different goat grazing management? Location: Cantabrian heathlands in Illano, Asturias, northern Spain. Methods: During 4 years, vegetation dynamics (structural composition, canopy height and floristic diversity) were studied under three goat grazing treatments with three replicates: high stocking rate (11.7 goats ha,1) with a local Celtiberic breed, and high (15 goats ha,1) and low (6.7 goats ha,1) stocking rates with a commercial Cashmere breed. Results: The relative cover of woody plants, particularly heather species, decreased more while herbaceous cover increased more under local Celtiberic than under Cashmere breed grazing. Within Cashmere treatments, the cover and height of live shrubs decreased more and the herbaceous cover increased more under high than under low stocking rate. Redundancy analysis showed a significant effect of treatment × year interaction on floristic composition. Greater species richness was recorded under local goat grazing, but Shannon diversity index fell in the fourth year on these plots because of dominance by two grass species. Conclusions: Local Celtiberic goat grazing at such a high stocking rate (11.7 goats ha,1) hinders the development of sustainable systems on these heathlands, both in environmental and productive terms, owing to the limitations in soil fertility. Nevertheless, Celtiberic goats could be useful for controlling excessive shrub encroachment and reducing fire hazard. Cashmere goat grazing at high stocking rate promoted the highest Shannon diversity by generating a better balance between woody and herbaceous plants, while shrub dominance was not altered under the low stocking rate. [source] Effects of Vegetation Thinning on Above- and Belowground Carbon in a Seasonally Dry Tropical Forest in MexicoBIOTROPICA, Issue 3 2009Rodrigo Vargas ABSTRACT Mature tropical forests are disappearing and secondary forests are becoming more abundant, thus there is an increasing need to understand the ecology and management of secondary forests. In the Yucatan Peninsula, Mexico, seasonally dry tropical forests are subject to frequent fire, and early-successional stands are extremely dense. We applied vegetation thinning (removal of all stems < 2 cm in diameter) to hasten secondary succession and open the understory to reduce the fire ladder in an 11-yr-old stand. We quantified the effect of vegetation thinning on above- and belowground carbon over 5 yr. Aboveground carbon included all standing vegetation and belowground carbon included fine roots and organic carbon in the Oi, Oe, and Oa soil horizons. Trees with diameter of 2,10 cm and > 10 cm had higher carbon accumulation rates in thinned plots than in control plots. Carbon stored in the Oi-horizon and the Oe > 2 mm fraction remained significantly higher in thinned plots even 5 yr after treatment. Carbon in fine roots was significantly higher in thinned plots, and radiocarbon (14C) data suggest that fine roots in thinned plots were recently produced in comparison with fine roots in control plots. We did not find significant differences in total ecosystem carbon after 5 yr (126 ± 6 and 136 ± 8 Mg C/ha, respectively). These results suggest rapid carbon recovery and support the hypothesis that young tropical forests thinned to hasten succession and reduce the fire hazard may have only a short-term negative impact on carbon accumulation in vegetation and soils. RESUMEN Los bosques tropicales maduros están desapareciendo y los bosques secundarios se han vuelto mas abundantes, por eso hay una creciente necesidad de entender la ecología y el manejo de los bosques secundarios. En la Península de Yucatán, México, los bosques secos de temporal están sujetos a frecuentes fuegos y los bosques secundarios son extremadamente densos. En este estudio se aplicó un aclareo de vegetación (remoción de todos los tallos < 2 cm en diámetro) para acelerar la sucesión secundaria y controlar el riesgo de fuego en un bosque de 11 años. Cuantificamos el efecto del aclaro de vegetación en el carbono arriba del suelo y el carbono bajo el suelo por cinco años. El carbono arriba del suelo incluyó toda la vegetación en pie y el carbono bajo el suelo incluyó raíces finas y el carbono orgánico de los horizontes Oi, Oe y Oa del suelo. Los árboles con diámetro entre 2,10 cm y > 10 cm tuvieron mayor acumulación de carbono en las parcelas de aclareo que en las control. El carbono guardado en el horizonte Oi y en la fracción Oe > 2 mm permaneció con niveles más altos en las parcelas de aclareo incluso cinco años después del tratamiento. El carbono en las raíces finas fue significativamente mayor en las parcelas con aclareo y los datos de radiocarbono (14C) sugieren que las raíces finas en las parcelas con aclareo fueron producidas después que las raíces finas en las parcelas control. No encontramos diferencias en el carbono total del ecosistema entre las parcelas control y las de aclareo después de cinco años (126 ± 6 and136 ± 8 Mg C/ha, respectivamente). Estos resultados sugieren una rápida recuperación del carbono y apoyan la hipótesis de que el aclareo para acelerar la sucesión y controlar el riesgo de fuego en bosques tropicales tempranos solo tiene un efecto negativo a corto plazo en la acumulación de carbono del suelo y vegetación. [source] Fire hazard evaluation of thermoplastics based on analytic hierarchy process (AHP) methodFIRE AND MATERIALS, Issue 5 2010Baogang Yu Abstract Combustibility performance of 14 compositions including five main thermoplastics (polycarbonate (PC), polypropylene (PP), high impact polystyrene (HIPS), acrylonitrile butadiene styrene (ABS) and poly (vinyl chloride) (PVC)) was tested by cone calorimeter. The fire growth index, total heat release amount index, total smoke release amount index and toxicity product index were calculated, based on which an index system for evaluating fire hazard was set up. All factors in this index system had been analyzed by the analytic hierarchy process, and the specific weight for each factor had been determined. Then fire hazard of thermoplastics was evaluated considering integrated fire hazard index. The results show that fire hazards of HIPS-phosphate fire retardant (PFR), PVC-non-flame retardant, ABS-brominated flame retardant (BFR) and PC/ABS-PFR are higher than PC-BFR and PP-non-halogenated flame retardant. Copyright © 2009 John Wiley & Sons, Ltd. [source] Investigation and correlation of manikin and bench-scale fire testing of clothing systemsFIRE AND MATERIALS, Issue 6 2002Calvin Lee The US Army currently has five flame/thermal protective clothing systems to provide protection for soldiers against fire hazards. The protective performance of these clothing systems against burn injuries was investigated in full-scale manikin tests. The protective performance of fabric layers of these clothing systems was also examined in bench-scale tests. In addition, air gap thicknesses and distributions of the five clothing systems were determined by using a three-dimensional laser scanning technique. In this paper, test conditions of the manikin and bench-scale tests are compared, and the test results are correlated in light of the air gap measurements. The behavior of individual sensors on the manikin with similar test conditions to those of bench-scale tests are compared with the bench-scale tests. It is found that if the air gap distribution of a clothing system is known, bench-scale tests could provide useful information for full-scale performance, especially bench-scale tests with zero air gap measurements. Published in 2002 by John Wiley & Sons, Ltd. [source] Coarse woody debris in Australian forest ecosystems: A reviewAUSTRAL ECOLOGY, Issue 8 2005GEMMA WOLDENDORP Abstract Coarse woody debris (CWD) is the standing and fallen dead wood in a forest and serves an important role in ecosystem functioning. There have been several studies that include estimates of CWD in Australian forests but little synthesis of these results. This paper presents findings from a literature review of CWD and fine litter quantities. Estimates of forest-floor CWD, snags and litter from the literature are presented for woodland, rainforest, open forest and tall open forest, pine plantation and native hardwood plantation. Mean mass of forest floor CWD in Australian native forests ranged from 19 t ha,1 in woodland to 134 t ha,1 in tall open forest. These values were generally within the range of those observed for similar ecosystems in other parts of the world. Quantities in tall open forests were found to be considerably higher than those observed for hardwood forests in North America, and more similar to the amounts reported for coniferous forests with large sized trees on the west coast of the USA and Canada. Mean proportion of total above-ground biomass as forest floor CWD was approximately 18% in open forests, 16% in tall open forests, 13% in rainforests, and 4% in eucalypt plantations. CWD can be high in exotic pine plantations when there are considerable quantities of residue from previous native forest stands. Mean snag biomass in Australian forests was generally lower than the US mean for snags in conifer forests and higher than hardwood forest. These results are of value for studies of carbon and nutrient stocks and dynamics, habitat values and fire hazards. [source] | ||||||||||