Improving the accuracy of fire behavior prediction requires better understanding of live fuel, the dominant component of tree crowns, which dictates the consumption and energy release of the crown fire flame-front. Live fuel flammability is not well represented by existing evaluation methods. High-flammability live fuel, e.g., in conifers, may maintain or increase the energy release of the advancing crown fire flame-front, while low-flammability live fuel, e.g., in boreal deciduous stands, may reduce or eventually suppress flame-front energy release. To better characterize these fuel–flame-front interactions, we propose a method for quantifying flammability as the fuel’s net effect on (contribution to) the frontal flame energy release, in which the frontal flame is simulated using a methane diffusion flame. The fuel’s energy release contribution to the methane flame was measured using oxygen consumption calorimetry as the difference in energy release between the methane flame interacting with live fuel and the methane flame alone. In-flame testing resulted in fuel ignition and consumption comparable to those in wildfires. The energy release contribution of live fuel was significantly lower than its energy content measured using standard methods, suggesting better sensitivity of the proposed metric to water content- and oxygen deficiency-associated energy release reductions within the combustion zone.

Existing test methods for determining of thermal protection from fire offered by textiles are typically characterized by the exposure of specimens to a controlled flame and measurement of energy transferred through the specimen. The measured energy transfer is then used to differentiate materials or further processing (burn injury prediction) is used as a basis for comparison. The test conditions are set by measuring the energy transferred to the sensor or sensors in absence of a test specimen. In order to represent a potential hazard and provide good differentiation among tested materials, an exposure heat flux is required that allows for rapid and substantial increase in the temperature of the tested specimen. A specified heat flux of 80-84 kW/m(2) is common in both bench-scale and full-scale tests. Because of the use of controlled flame and significant energy transfer rates involved in these tests, there is a common misconception that these test methods constitute a simulation of a particular hazard, especially with regard to the hazard of hydrocarbon flash fires. In order to provide a basis for comparing specified test conditions with real-world hazard conditions, a series of heat flux measurements were performed on propane-fueled flash fires in open air. In each test, an array of heat flux sensors was positioned around a propane source. A large fuel cloud was allowed to form and subsequently ignited using a pilot flame. These experiments were carried out outdoors and as such were subject to prevailing wind currents. Because of the potentially high variability, more than 50 separate fuel releases were undertaken. The output of the array of sensors was used to determine the intensity and duration of each flash fire event. In addition to the array of heat flux sensors, an instrumented mannequin was constructed to measure the heat flux incident on a human form within the flash fire. The results indicate that there was significant variability in the conditions in each fire due to the open air conditions creating unpredictable distribution of fuel and air. Flash fires occurred that were less severe and more severe than the conditions used in standardized laboratory testing.

The number of lost-time accidents associated with hot fluids and steam is of the same magnitude as those attributed to flash fire, yet little attention has been paid to protection against these hazards. Conventional materials that are used in the petrochemical industry for protection against short-duration flash fires do not perform well against either a hot liquid or steam hazard primarily because the fluid is able to penetrate the materials. ASTM F2701, Evaluating Heat Transfer Through Materials for Protective Clothing. Upon Contact with a Hot Liquid Splash, was compared to two other similar test methods developed at the University of Alberta. Tests of the three methods were conducted using materials intended to protect individuals against a hot liquid splash. All materials used in the evaluation contained either a semipermeable membrane (polytetrafluoroethylene or polyurethane) or were impermeable to liquid penetration; as a result, energy transfer rates were low in comparison to permeable, or more conventional, flame-resistant materials. The analysis used in the evaluation of test methods utilized energy absorbed at the sensor surface rather than Stoll because, in most cases, the materials were protective enough to prevent burn injury under the chosen fluid temperatures and exposure durations. Both alternative test methods were found to provide superior differentiation among fabrics compared to the existing standard. In the set of fabrics tested (a mix of semipermeable and impermeable), SPSS (a statistical package) was used to evaluate test results. The ASTM F2701 method was only able to separate the samples into three groups based on energy transferred through the material. Both alternative test methods were able to separate the test fabrics into six distinct groups, indicating that both alternative tests provided better differentiation among fabrics than ASTM F2701.

Within the kitchen the potential for burn injuries arising from contact with hot surfaces, flames, hot liquid, and steam hazards is high. The chef's uniform can potentially offer some protection against such burns by providing a protective barrier between the skin and the thermal hazard, although the extent to which can provide some protection is unknown. The purpose of this study was to examine whether fabrics used in chefs' uniforms were able to provide some protection against thermal hazards encountered in the kitchen. Fabrics from chefs' jackets and aprons were selected. Flammability of single- and multiple-layered fabrics was measured. Effect of jacket type, apron and number of layers on hot surface, hot water, and steam exposure was also measured. Findings showed that all of the jacket and apron fabrics rapidly ignited when exposed to a flame. Thermal protection against hot surfaces increased as layers increased due to more insulation. Protection against steam and hot water improved with an impermeable apron in the system. For wet thermal hazards increasing the number of permeable layers can decrease the level of protection due to stored thermal energy. As the hands and arms are most at risk of burn injury increased insulation and water-impermeable barrier in the sleeves would improve thermal protection with minimal compromise to overall thermal comfort.

Kitchen workers sustain one of the highest rates of occupational burn injuries through exposure to the various thermal hazards present in institutional and restaurant kitchens. The jacket of the chefs' uniform has the potential to act as a protective garment, although the extent of the protection afforded by this clothing has not been examined. This study evaluates a selection of current fabrics used in chefs' uniform jackets to determine their effectiveness in providing protection against hot surface contact, hot liquids and low-pressure steam burns. Four jacket fabrics and two apron fabrics were tested as single layers and in layered combinations. Results showed that single-layered fabrics offered less protection against hot surface contact burns than double-layered fabrics, as an increase in fabric thickness improved thermal insulation of the system. Fabrics covered with a water-impermeable apron layer afforded the greatest protection against hot water and low-pressure steam, while fabrics covered with a permeable apron layer did not provide additional protection. It was found that the addition of the permeable apron fabric layer stored more thermal energy when exposed to hot water, potentially reducing the protection offered by the layered fabric systems.

The decomposition of flame resistant (FR) materials, either through elevated temperature or contact with flames, results in a range of chemical species, some of which can be quite toxic to humans. Small scale or bench scale tests for decomposition products have been done in the past, but there were always questions as to whether these were representative of full-scale flash fire test results. To determine whether the decomposition products would be of sufficient quantity to measure and whether different FR materials would produce a "signature" set of compounds, full scale testing was undertaken. Coveralls constructed from four common FR materials were evaluated. The methodology used allowed the determination of the thermal decomposition products of FR materials when exposed to flash fire.

A hot liquid splash tester and a protocol were developed to investigate the thermal protective performance and impact penetration performance of fabrics used in protective clothing. The instrument developed could be used to characterize penetration resistance and thermal protection against hot liquid splash. Different liquids were employed to explore the effect of liquid properties on penetration performance and thermal protection. The correlation between penetration and thermal protection was discussed. The results showed that liquid viscosity and fabric surface property determined the impact penetration. Impermeable fabrics showed better protection than permeable fabrics. Increasing penetration resistance improved thermal protection of a permeable fabric. Liquid thermal diffusivity, mass transfer rate and total amount affected heat transfer through the fabric to skin simulant. The findings will provide technical data to improve protective material performance and modify test standard. Crown Copyright (c) 2012 Published by Elsevier Inc. All rights reserved.

The thermal protective performance of fabrics against hot liquid splashes was investigated under different configurations. The air gap of 6 mm between specimen and sensor was simulated and compared with direct contact configuration. Three liquids (distilled water, canola oil, drilling mud) at 85℃ were applied as challenge hot liquid hazards. The results showed that fabric permeability significantly affected heat transfer due to the occurrence of mass transfer both with and without a spacer. The absorbed energy and second-degree burn time presented significantly negative correlation. The effect of air gap on thermal performance was investigated. The findings demonstrated that minimizing mass transfer could effectively improve thermal protection against hot liquid splashes and the existing of an air layer could improve thermal performance.

This study explores the behavior of textile fabrics under thermal exposures. The performance of thermal protective textile fabric systems with different structural features was evaluated under laboratory simulated thermal exposures. The study demonstrated that the protective performance of textile fabric systems varies with different types of thermal exposure. To provide effective protection in flame and radiant-heat exposures, the most important fabric properties to address are emissivity, absorptivity and thermal resistance. In hot surface exposures, the compression property of the fabric systems is the primary feature to consider for protection. Hot water and steam exposures produce mass transfer through fabrics. In the presence of water or steam jet pressure, fabric compression is a primary factor in protecting the human body. The findings obtained in this study can be used to engineer fabric systems that provide better protection from various thermal exposures.

Setting up a manikin/burner system to evaluate FR clothing requires that the energy transfer to the surface of an instrumented manikin be measured and adjusted to meet the requirements of the test method being used (ASTM F1930 or ISO 11056). ISO 11056 makes provision for the use of an instrumented cylinder to initially set the physical position of burners before using the manikin. The idea behind the provision is that because of the symmetry of the cylinder the heat flux should be uniform over the surface enabling rapid initial setting of burner positions, fuel pressures, flow controls etc. This work experimentally evaluated the differences in heat flux that would be obtained if conditions were set with a cylinder and the cylinder then replaced with the manikin for. The work was undertaken as background to find out whether this procedure would be a useful addition to ASTM F1930. The study concluded that the additional cost/time associated with using a cylinder did not result in better exposure conditions on a manikin form primarily due to the non-uniform shape of the manikin.

A laboratory simulation was performed to study the thermal protective performance of fabric systems under low level thermal hazards in the range of 6.3-8.3 kW/m(2). Two approaches were used. The first used a method similar to the ASTM F 1939, radiant heat resistance test, while the second used a modification designed to capture the contribution to skin burn injury due to energy stored in the test specimens being released after the direct exposure had ended. Both dry and wet specimens were tested. In order to accommodate the prolonged exposure time a water cooled heat flux sensor was used to calibrate the radiant heat source and measure the energy directly transmitted through during the exposure and discharged later from the fabric systems. The Henriques Burn Integral (HBI) was adopted and programmed with a three layer skin model to predict the time required to achieve a second degree skin burn injury. The study investigated the thermal protection provided by the clothing with different layering and examined the effect of moisture under low level radiant heat exposures. In addition, the physiological burden associated with wearing the clothing was predicted and compared. The results obtained show the difference in measured protection level under low radiant heat from these two approaches and demonstrate that the stored thermal energy released from the clothing system significantly lowers the measured thermal protective performance.