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A. Ganteaume - One of the best experts on this subject based on the ideXlab platform.
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Assessing and ranking the flammability of ornamental species in WUI (SE France).
2012Co-Authors: A. Ganteaume, M. Jappiot, Romain Esteve, A. N'diaye, C. Lampin, F. Guerra, J.m. Lopez, M. Guijarro, C. Hernando-laraAbstract:Fire risk is high in Wildland-Urban Interfaces (WUI) and WUI fires, burning the surrounding ornamental vegetation, are often transmitted to structures. Thus, to be able to use fire-wise species in such locations, the assessment and ranking of the flammability of ornamental plant species are required. The flammability of seven species, among those most frequently planted in hedges in SE France, was studied, under laboratory conditions, at two levels: live leaf and litter. Leaf characteristics (FMC, mass, surface, volume, S/V ratio) were measured and the flammability parameters (Ignition frequency, Time-to-Ignition, flaming duration) were recorded using an epiradiator as burning device. The Gross Heat of Combustion (GHC) was measured by calorimetry. The flammability parameters (Ignition frequency, Time-to-Ignition, flaming duration and initial flame propagation) as well as the bulk density of the undisturbed litter samples were recorded during burning experiments performed on a fire bench. Regarding live leaves, burning experiments showed that Phyllostachys sp. and Photinia fraseri had higher ignitability (along with Pyracantha coccinea) and sustainability and were characterized by low FMC whereas Pittosporum tobira and Nerium oleander had lower ignitability and were characterized by high GHC. Prunus laurocerasus and Cupressus sempervirens had lower sustainability and were characterized by low S/V ratio. Regarding litters, Cupressus sempervirens and Pyracantha coccinea (high proportions of scale-leaves and/or fine particles and high bulk density) presented higher sustainability, ignitability (high Ignition frequency), along with Photinia fraseri, and lowest combustibility (low flame propagation) along with Pittosporum tobira. The latter, characterized by high proportions of debris, coarse particles and evergreen leaves, was the least ignitable (high Time-to-Ignition) along with litters of Pyracantha coccinea and Nerium oleander, and had lower sustainability along with those of Phyllostachys sp. and Nerium. Litters of Prunus laurocerasus, Photinia fraseri and Phyllostachys had better combustibility (high proportions of debris) and the latter was also quick to ignite. Hierarchical cluster analysis performed on the flammability parameters recorded during both types of experiments ranked the seven species in four distinct clusters from the most flammable (Phyllostachys sp. and Photinia fraseri) to the least flammable (Pittosporum tobira and Nerium oleander); the other species displaying two groups of intermediate flammabilities (Prunus laurocerasus-Pyracantha coccinea and Cupressus sempervirens ). Further flammability experiments on the whole plant are needed and the highly flammable species should not be used in hedges planted in WUIs in SE France.
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Effects of vegetation type and fire regime on flammability of undisturbed litter in Southeastern France
Forest Ecology and Management, 2011Co-Authors: A. Ganteaume, M. Jappiot, C. Lampin-maillet, T. Curt, L. BorgnietAbstract:to assess the effect of vegetation types and of fire regime on the flammability of dead fuels, samples of litter were collected undisturbed (i.e. keeping the structure of litter layers) in 29 study sites spread over the limestone-derived soils of Provence. The sampling plan comprised the most representative ecosystems of the study area: pure Pinus halepensis stands, mixed pine-oak stands and shrublands. Three classes of litter depth were studied (low, medium and high) to account for the variability existing in the field. Sampling also included the number of fires in each site since 1960 (no fire, 1 or 2 fires and ≥3 fires) and the Time interval since the last fire (≤15 years, 15–45 years and >45 years). Flammability experiments were carried out in laboratory using a glowing firebrand and a 10 kmh−1 wind. The main variables recorded were: Ignition frequency, Time-to-Ignition, flaming duration, flame rate of spread, flame propagation, mean flame temperature, maximum flame height and rate of consumption. Results showed that the Ignition frequency was higher in mixed stands than in pure pine stands whereas the Time-to Ignition, flaming duration and rate of consumption were the highest in pure pine stands. The maximum flame height and the flame propagation decreased with the increase of the number of fires and the Time-to-Ignition was the highest when the interval since the last fire was the shortest. Increases in litter depth resulted in increased mean flame temperature, maximum flame height and flame propagation. These results can be explained, in part, by the proportions of the different litter components.
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Effects of vegetation types and fire regime on the flammability of non-reconstructed litters sampled in limestone Provence (SE France).
2009Co-Authors: A. Ganteaume, M. Jappiot, C. Lampin-maillet, T. Curt, L. Borgniet, Romain Esteve, William Martin, A. N'diayeAbstract:Knowledge about wildland fuel is essential to fire prevention and to both biodiversity conservation and reduction of the negative impacts of fire. Little is known of flammability of dead fuels, especially for non-reconstructed samples that are hypothesized to represent the field conditions.to assess the impact of vegetation types and of fire regime on the flammability of dead fuels, samples of litter were collected undisturbed (i.e. keeping the structure of litter layers) in 30 study sites spread over the limestone Provence. The sampling plan comprised the most representative ecosystems of the study area: pure Pinus halepensis stands, mixed pine-oak stands and shrublands. Three classes of litter depth were studied (low, medium and high) to account the variability existing in the field. Sampling also included the number of fires in each site since 1960 (no fire, 1 or 2 fires and ≥3 fires) and the Time interval since the last fire (> 40 years, interval 40-15 years and ≤15 years).Flammability experiments were carried out in laboratory using a glowing firebrand and a 10 km.h-1 wind. The main variables recorded were: Ignition frequency, Time-to-Ignition, flaming duration, flame rate of spread, flame propagation, mean flame temperature, mean flame height and rate of consumption.Results showed that the Ignition frequency was higher in mixed stands than in pure pine stands whereas the Time-to Ignition, flaming duration and rate of consumption were the highest in pure pine stands. The mean flame height and the flame propagation decreased with the increase of the number of fires and the Time-to-Ignition was the highest when the interval since the last fire was the shortest. The increase of the litter depth entailed an increase of the mean flame temperature, the mean flame height and the flame propagation. The characteristics of litter samples explained in part these results.
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Comparison of the disturbed litter flammability on calcareous soils and acidic soils in Southern France
2008Co-Authors: A. Ganteaume, M. Jappiot, C. Lampin-maillet, T. Curt, L. Borgniet, Romain Esteve, William Martin, A. Schaffhauser, A. N'diaye Boubacar, J. BaudelAbstract:Knowledge about fuel vegetation is a fundamental part of the fire management that is necessary to both conserve biodiversity and reduce the negative impacts of wildland fires. On the framework of the European programme FireParadox, flammability characteristics of dead fuels were described in Southern France on both acidic and calcareous soils according to fire modalities (no fire since 1960, 1 and more fires old and recent), to assess if they were influenced by the past fire regime, influencing in turn the vegetation dynamics. Samples of disturbed litters have been collected in representative ecosystems of southern France : (i) on calcareous soils, in high stands of Pinus halepensis and of mixed oak-pine, in medium-sized stands of P. halepensis and mixed oak-pine with understorey and in garrigue (shrubland); and (ii) on acidic soils, in high Quercus suber stands, high maquis and lower maquis. The low and medium-sized stands come from a post-fire succession, the highest biodiversity, in terms of specific richness occurring between 4 and 11 years after the fire. to assess the flammability of these litters, several series of tests were conducted in laboratory, using a glowing firebrand and a wind speed of 10 km.h-1. The main parameters recorded were Time to Ignition, flaming duration, flame propagation. For the low (garrigue and low maquis) and the medium-sized (pure pine or mixed pine-oak stands with understorey and higher maquis) stands where biodiversity is maximum, the comparison between litters collected on calcareous soils and on acidic soils shows no significant difference for all the parameters. For the high mature stands, where biodiversity is the lowest, especially in Pine stands, the comparison between the both sets of litters shows that there is a significant difference only for the Time to Ignition which is much higher on acidic soils (73s) than on calcareous soils (17s). These results suggest that the Quercus suber litter collected on acidic soils is less flammable than the litter collected on calcareous soils.
Charles A Wilkie - One of the best experts on this subject based on the ideXlab platform.
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comparative study on the flammability of polyethylene modified with commercial fire retardants and a zinc aluminum oleate layered double hydroxide
Polymer Degradation and Stability, 2009Co-Authors: Charles Manzinshuti, Jeanne M Hossenlopp, Charles A WilkieAbstract:Abstract Polyethylene (PE) was modified by the addition of a layered double hydroxide of zinc aluminum oleate (ZnAl) and/or commercial fire retardants. Commercial additives included: melamine polyphosphate (MPP), ammonium polyphosphate (APP), triphenol phosphate (TPP), resorcinol diphosphate (RDP), decabromophenyl oxide (DECA) and antimony oxide (AO). The thermal stability and the combustion behaviors of the new composite polymeric materials are evaluated in TGA experiments and cone calorimetry. At 20% total additive loading, APP and LDH enhance the thermal stability of the PE composites and favor char formation. ZnAl leads to the best reduction in the peak of heat release rate (PHRR), 72%, while the combinations of PE with other additives give reductions in the range 20–40%. The combination of DECA and AO effectively increases the Time to Ignition and Time to PHRR while LDH lowers these two parameters. APP and MPP on the other hand, do not affect the Time to Ignition, but they effectively increase the Time to PHRR relative to the pristine polymer.
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thermal stability and flammability characteristics of ethylene vinyl acetate eva composites blended with a phenyl phosphonate intercalated layered double hydroxide ldh melamine polyphosphate and or boric acid
Polymer Degradation and Stability, 2009Co-Authors: Calistor Nyambo, Everson Kandare, Charles A WilkieAbstract:A phenyl phosphonate-intercalated MgAl-LDH (MgAl-PPh), melamine polyphosphate (MP), and boric acid (BA) were independently and concomitantly added to neat ethylene vinyl acetate (EVA) copolymer at loading fractions of 10% (w/w). The structural morphology of MgAl-PPh was established via powder X-ray diffraction (PXRD) and scanning electron microscopy (SEM) while the presence of phenyl phosphonate in the galleries was confirmed by Fourier transform infrared (FTIR). Thermogravimetric analysis (TGA) and cone calorimetry were used to evaluate the thermal stability and flammability behavior of EVA and its composites. While Time-to-Ignition is greatly reduced for EVA composites compared to the virgin polymer, there are remarkable reductions in the peak heat release rate (PHRR) which relates to a reduction in flame intensity. Synergistic effects were observed in cone calorimetry for the formulation containing MgAl-PPh, MP, and BA.
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flame retarded polystyrene investigating chemical interactions between ammonium polyphosphate and mgal layered double hydroxide
Polymer Degradation and Stability, 2008Co-Authors: Calistor Nyambo, Dongyan Wang, Everson Kandare, Charles A WilkieAbstract:Potential flame retardants, MgAl-LDH and ammonium polyphosphate (APP), were added to neat polystyrene (PS) individually or in combinations at weight fractions no greater than 10%. Structural morphologies of MgAl-LDH and the corresponding PS nanocomposites were established via X-ray diffraction (XRD) and transmission electron microscopy (TEM). Thermogravimetric analysis (TGA) and cone calorimetry were used to study the thermal stability and fire performance of the composites. Time to Ignition is greatly reduced for PS composites when compared to the virgin polymer. Synergistic effects were observed in both TGA and cone calorimetry for formulations containing both MgAl-LDH and APP. Physical and chemical interactions between MgAl-LDH and APP are responsible for the observed synergy in thermal stability and fire performance.
L. Borgniet - One of the best experts on this subject based on the ideXlab platform.
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Effects of vegetation type and fire regime on flammability of undisturbed litter in Southeastern France
Forest Ecology and Management, 2011Co-Authors: A. Ganteaume, M. Jappiot, C. Lampin-maillet, T. Curt, L. BorgnietAbstract:to assess the effect of vegetation types and of fire regime on the flammability of dead fuels, samples of litter were collected undisturbed (i.e. keeping the structure of litter layers) in 29 study sites spread over the limestone-derived soils of Provence. The sampling plan comprised the most representative ecosystems of the study area: pure Pinus halepensis stands, mixed pine-oak stands and shrublands. Three classes of litter depth were studied (low, medium and high) to account for the variability existing in the field. Sampling also included the number of fires in each site since 1960 (no fire, 1 or 2 fires and ≥3 fires) and the Time interval since the last fire (≤15 years, 15–45 years and >45 years). Flammability experiments were carried out in laboratory using a glowing firebrand and a 10 kmh−1 wind. The main variables recorded were: Ignition frequency, Time-to-Ignition, flaming duration, flame rate of spread, flame propagation, mean flame temperature, maximum flame height and rate of consumption. Results showed that the Ignition frequency was higher in mixed stands than in pure pine stands whereas the Time-to Ignition, flaming duration and rate of consumption were the highest in pure pine stands. The maximum flame height and the flame propagation decreased with the increase of the number of fires and the Time-to-Ignition was the highest when the interval since the last fire was the shortest. Increases in litter depth resulted in increased mean flame temperature, maximum flame height and flame propagation. These results can be explained, in part, by the proportions of the different litter components.
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Effects of vegetation types and fire regime on the flammability of non-reconstructed litters sampled in limestone Provence (SE France).
2009Co-Authors: A. Ganteaume, M. Jappiot, C. Lampin-maillet, T. Curt, L. Borgniet, Romain Esteve, William Martin, A. N'diayeAbstract:Knowledge about wildland fuel is essential to fire prevention and to both biodiversity conservation and reduction of the negative impacts of fire. Little is known of flammability of dead fuels, especially for non-reconstructed samples that are hypothesized to represent the field conditions.to assess the impact of vegetation types and of fire regime on the flammability of dead fuels, samples of litter were collected undisturbed (i.e. keeping the structure of litter layers) in 30 study sites spread over the limestone Provence. The sampling plan comprised the most representative ecosystems of the study area: pure Pinus halepensis stands, mixed pine-oak stands and shrublands. Three classes of litter depth were studied (low, medium and high) to account the variability existing in the field. Sampling also included the number of fires in each site since 1960 (no fire, 1 or 2 fires and ≥3 fires) and the Time interval since the last fire (> 40 years, interval 40-15 years and ≤15 years).Flammability experiments were carried out in laboratory using a glowing firebrand and a 10 km.h-1 wind. The main variables recorded were: Ignition frequency, Time-to-Ignition, flaming duration, flame rate of spread, flame propagation, mean flame temperature, mean flame height and rate of consumption.Results showed that the Ignition frequency was higher in mixed stands than in pure pine stands whereas the Time-to Ignition, flaming duration and rate of consumption were the highest in pure pine stands. The mean flame height and the flame propagation decreased with the increase of the number of fires and the Time-to-Ignition was the highest when the interval since the last fire was the shortest. The increase of the litter depth entailed an increase of the mean flame temperature, the mean flame height and the flame propagation. The characteristics of litter samples explained in part these results.
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Comparison of the disturbed litter flammability on calcareous soils and acidic soils in Southern France
2008Co-Authors: A. Ganteaume, M. Jappiot, C. Lampin-maillet, T. Curt, L. Borgniet, Romain Esteve, William Martin, A. Schaffhauser, A. N'diaye Boubacar, J. BaudelAbstract:Knowledge about fuel vegetation is a fundamental part of the fire management that is necessary to both conserve biodiversity and reduce the negative impacts of wildland fires. On the framework of the European programme FireParadox, flammability characteristics of dead fuels were described in Southern France on both acidic and calcareous soils according to fire modalities (no fire since 1960, 1 and more fires old and recent), to assess if they were influenced by the past fire regime, influencing in turn the vegetation dynamics. Samples of disturbed litters have been collected in representative ecosystems of southern France : (i) on calcareous soils, in high stands of Pinus halepensis and of mixed oak-pine, in medium-sized stands of P. halepensis and mixed oak-pine with understorey and in garrigue (shrubland); and (ii) on acidic soils, in high Quercus suber stands, high maquis and lower maquis. The low and medium-sized stands come from a post-fire succession, the highest biodiversity, in terms of specific richness occurring between 4 and 11 years after the fire. to assess the flammability of these litters, several series of tests were conducted in laboratory, using a glowing firebrand and a wind speed of 10 km.h-1. The main parameters recorded were Time to Ignition, flaming duration, flame propagation. For the low (garrigue and low maquis) and the medium-sized (pure pine or mixed pine-oak stands with understorey and higher maquis) stands where biodiversity is maximum, the comparison between litters collected on calcareous soils and on acidic soils shows no significant difference for all the parameters. For the high mature stands, where biodiversity is the lowest, especially in Pine stands, the comparison between the both sets of litters shows that there is a significant difference only for the Time to Ignition which is much higher on acidic soils (73s) than on calcareous soils (17s). These results suggest that the Quercus suber litter collected on acidic soils is less flammable than the litter collected on calcareous soils.
M. Jappiot - One of the best experts on this subject based on the ideXlab platform.
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Assessing and ranking the flammability of ornamental species in WUI (SE France).
2012Co-Authors: A. Ganteaume, M. Jappiot, Romain Esteve, A. N'diaye, C. Lampin, F. Guerra, J.m. Lopez, M. Guijarro, C. Hernando-laraAbstract:Fire risk is high in Wildland-Urban Interfaces (WUI) and WUI fires, burning the surrounding ornamental vegetation, are often transmitted to structures. Thus, to be able to use fire-wise species in such locations, the assessment and ranking of the flammability of ornamental plant species are required. The flammability of seven species, among those most frequently planted in hedges in SE France, was studied, under laboratory conditions, at two levels: live leaf and litter. Leaf characteristics (FMC, mass, surface, volume, S/V ratio) were measured and the flammability parameters (Ignition frequency, Time-to-Ignition, flaming duration) were recorded using an epiradiator as burning device. The Gross Heat of Combustion (GHC) was measured by calorimetry. The flammability parameters (Ignition frequency, Time-to-Ignition, flaming duration and initial flame propagation) as well as the bulk density of the undisturbed litter samples were recorded during burning experiments performed on a fire bench. Regarding live leaves, burning experiments showed that Phyllostachys sp. and Photinia fraseri had higher ignitability (along with Pyracantha coccinea) and sustainability and were characterized by low FMC whereas Pittosporum tobira and Nerium oleander had lower ignitability and were characterized by high GHC. Prunus laurocerasus and Cupressus sempervirens had lower sustainability and were characterized by low S/V ratio. Regarding litters, Cupressus sempervirens and Pyracantha coccinea (high proportions of scale-leaves and/or fine particles and high bulk density) presented higher sustainability, ignitability (high Ignition frequency), along with Photinia fraseri, and lowest combustibility (low flame propagation) along with Pittosporum tobira. The latter, characterized by high proportions of debris, coarse particles and evergreen leaves, was the least ignitable (high Time-to-Ignition) along with litters of Pyracantha coccinea and Nerium oleander, and had lower sustainability along with those of Phyllostachys sp. and Nerium. Litters of Prunus laurocerasus, Photinia fraseri and Phyllostachys had better combustibility (high proportions of debris) and the latter was also quick to ignite. Hierarchical cluster analysis performed on the flammability parameters recorded during both types of experiments ranked the seven species in four distinct clusters from the most flammable (Phyllostachys sp. and Photinia fraseri) to the least flammable (Pittosporum tobira and Nerium oleander); the other species displaying two groups of intermediate flammabilities (Prunus laurocerasus-Pyracantha coccinea and Cupressus sempervirens ). Further flammability experiments on the whole plant are needed and the highly flammable species should not be used in hedges planted in WUIs in SE France.
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Effects of vegetation type and fire regime on flammability of undisturbed litter in Southeastern France
Forest Ecology and Management, 2011Co-Authors: A. Ganteaume, M. Jappiot, C. Lampin-maillet, T. Curt, L. BorgnietAbstract:to assess the effect of vegetation types and of fire regime on the flammability of dead fuels, samples of litter were collected undisturbed (i.e. keeping the structure of litter layers) in 29 study sites spread over the limestone-derived soils of Provence. The sampling plan comprised the most representative ecosystems of the study area: pure Pinus halepensis stands, mixed pine-oak stands and shrublands. Three classes of litter depth were studied (low, medium and high) to account for the variability existing in the field. Sampling also included the number of fires in each site since 1960 (no fire, 1 or 2 fires and ≥3 fires) and the Time interval since the last fire (≤15 years, 15–45 years and >45 years). Flammability experiments were carried out in laboratory using a glowing firebrand and a 10 kmh−1 wind. The main variables recorded were: Ignition frequency, Time-to-Ignition, flaming duration, flame rate of spread, flame propagation, mean flame temperature, maximum flame height and rate of consumption. Results showed that the Ignition frequency was higher in mixed stands than in pure pine stands whereas the Time-to Ignition, flaming duration and rate of consumption were the highest in pure pine stands. The maximum flame height and the flame propagation decreased with the increase of the number of fires and the Time-to-Ignition was the highest when the interval since the last fire was the shortest. Increases in litter depth resulted in increased mean flame temperature, maximum flame height and flame propagation. These results can be explained, in part, by the proportions of the different litter components.
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Effects of vegetation types and fire regime on the flammability of non-reconstructed litters sampled in limestone Provence (SE France).
2009Co-Authors: A. Ganteaume, M. Jappiot, C. Lampin-maillet, T. Curt, L. Borgniet, Romain Esteve, William Martin, A. N'diayeAbstract:Knowledge about wildland fuel is essential to fire prevention and to both biodiversity conservation and reduction of the negative impacts of fire. Little is known of flammability of dead fuels, especially for non-reconstructed samples that are hypothesized to represent the field conditions.to assess the impact of vegetation types and of fire regime on the flammability of dead fuels, samples of litter were collected undisturbed (i.e. keeping the structure of litter layers) in 30 study sites spread over the limestone Provence. The sampling plan comprised the most representative ecosystems of the study area: pure Pinus halepensis stands, mixed pine-oak stands and shrublands. Three classes of litter depth were studied (low, medium and high) to account the variability existing in the field. Sampling also included the number of fires in each site since 1960 (no fire, 1 or 2 fires and ≥3 fires) and the Time interval since the last fire (> 40 years, interval 40-15 years and ≤15 years).Flammability experiments were carried out in laboratory using a glowing firebrand and a 10 km.h-1 wind. The main variables recorded were: Ignition frequency, Time-to-Ignition, flaming duration, flame rate of spread, flame propagation, mean flame temperature, mean flame height and rate of consumption.Results showed that the Ignition frequency was higher in mixed stands than in pure pine stands whereas the Time-to Ignition, flaming duration and rate of consumption were the highest in pure pine stands. The mean flame height and the flame propagation decreased with the increase of the number of fires and the Time-to-Ignition was the highest when the interval since the last fire was the shortest. The increase of the litter depth entailed an increase of the mean flame temperature, the mean flame height and the flame propagation. The characteristics of litter samples explained in part these results.
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Comparison of the disturbed litter flammability on calcareous soils and acidic soils in Southern France
2008Co-Authors: A. Ganteaume, M. Jappiot, C. Lampin-maillet, T. Curt, L. Borgniet, Romain Esteve, William Martin, A. Schaffhauser, A. N'diaye Boubacar, J. BaudelAbstract:Knowledge about fuel vegetation is a fundamental part of the fire management that is necessary to both conserve biodiversity and reduce the negative impacts of wildland fires. On the framework of the European programme FireParadox, flammability characteristics of dead fuels were described in Southern France on both acidic and calcareous soils according to fire modalities (no fire since 1960, 1 and more fires old and recent), to assess if they were influenced by the past fire regime, influencing in turn the vegetation dynamics. Samples of disturbed litters have been collected in representative ecosystems of southern France : (i) on calcareous soils, in high stands of Pinus halepensis and of mixed oak-pine, in medium-sized stands of P. halepensis and mixed oak-pine with understorey and in garrigue (shrubland); and (ii) on acidic soils, in high Quercus suber stands, high maquis and lower maquis. The low and medium-sized stands come from a post-fire succession, the highest biodiversity, in terms of specific richness occurring between 4 and 11 years after the fire. to assess the flammability of these litters, several series of tests were conducted in laboratory, using a glowing firebrand and a wind speed of 10 km.h-1. The main parameters recorded were Time to Ignition, flaming duration, flame propagation. For the low (garrigue and low maquis) and the medium-sized (pure pine or mixed pine-oak stands with understorey and higher maquis) stands where biodiversity is maximum, the comparison between litters collected on calcareous soils and on acidic soils shows no significant difference for all the parameters. For the high mature stands, where biodiversity is the lowest, especially in Pine stands, the comparison between the both sets of litters shows that there is a significant difference only for the Time to Ignition which is much higher on acidic soils (73s) than on calcareous soils (17s). These results suggest that the Quercus suber litter collected on acidic soils is less flammable than the litter collected on calcareous soils.
Brian F. Gray - One of the best experts on this subject based on the ideXlab platform.
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Burning down the house: the Time to Ignition of an irradiated solid
Proceedings of the Royal Society of London. Series A: Mathematical Physical and Engineering Sciences, 1998Co-Authors: Lawrence K. Forbes, Brian F. GrayAbstract:The combustion of a wooden door irradiated with thermal energy is studied in this paper. The problem is relevant to the mechanism by which house fires propagate, for example. A novel method is presented for computing the Time–dependent behaviour of the temperature, which is also a function of a spatial coordinate. A boundary–integral method is used to reduce the mathematical formulation of the problem to a coupled system of Volterra–type integral equations, combined with a nonlinear rate equation. An efficient numerical method is used to solve this system with great accuracy. The Time to Ignition is obtained from these numerical solutions, and we show that spatial effects can cause an Ignition event to occur at lower values of the incident radiation than would be expected from the classical steady–state Ignition diagram. This is expected to have important consequences in understanding fire spread in buildings.
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The prediction of a practical lower bound for Ignition delay Times and a method of scaling Times-to-Ignition in large reactant masses from laboratory data
Symposium (International) on Combustion, 1991Co-Authors: Brian F. Gray, J.h. Merkin, J.f. GriffithsAbstract:In Part I a new theoretical basis was presented for predicting the Time-to-Ignition in a system that undergoes spontaneous combustion. A lower bound for the Time-to-Ignition of a self-igniting material was derived in the universally applicable form: τ i = u a 2 e 1 / u a ( 1 − e − Δ / u a 2 ) ( 1 ) where Time to Ignition and ambient temperature are expressed in dimensionless terms. Part II presents experimental support for the equation using the self-Ignition of cotton fibre. The data illustrates the convergence of three laboratory-scale studies of cotton to the lower bound relationship at higher degrees of supercriticality. This validates the use of the equation for prediction of safe storage Times in large scale stockpiles of material. The method can be applied to any self-heating material to give a series of data that form a family of curves in relation to the lower bound equation. The accuracy of Time-to-Ignition measurements in the laboratory is shown to be dependent on the suppression of self-heating around the periphery of the material. It is demonstrated both mathematically and experimentally that self-heating occurs at the periphery of a sample before any self-heating begins at its centre. Previously reported Ignition Times that do not account for peripheral effects are unsuitable for prediction purposes and would fall short of the lower bound equation. A nitrogen atmosphere was used as the pre-treatment to suppress the unwanted temperature profile of the cotton as it warmed up to ambient temperature. While nitrogen reduces the effect it does not suppress peripheral self-heating in the laboratory. Furthermore it does not suppress self-Ignition either and there are implications here for industrial scale attempts to control spontaneous combustion with inert atmospheres like nitrogen.
