Sealability Properties of Fluorine-Free Fire-Fighting Foams (FfreeF)

This contribution compares the sealability performance of recently developed three synthetic foam formulations (that do not contain fluorosurfactants or fluoropolymers) with that of an aqueous film forming foam (AFFF). We apply the sealability methodology outlined in the Australian Defence Force Specification, DEF(AUST)5706. This methodology specifies a 0.28 m² small-scale indoor fire pan. The pan is first filled with 10 L of water and then 5 L of AVGAS (aviation gasoline, flash point of −50°C) or heptane (flash point of −4°C) is placed on top of the water. Foams were generated from a pressurised extinguisher with a foam nozzle as described in the standard’s specification, set to create foams with expansion of 4:1. The foam spread across the fuel until the entire fuel surface was covered with foam. At 5 min intervals, a lit taper was introduced into the space above the pan area by passing it twice around the surface of the foam in a circular motion at a height of approximately 15 mm from the surface of the foam. The results demonstrate differences in the sealability performance between AFFF and fluorine-free foams (FfreeF). Under laboratory conditions, with a foam blanket 1–2 cm deep, best-performing FfreeF formulation (RF6) provides about 30% of the durability of an AFFF for protection against evaporation of low-flashpoint flammable liquids. We also note in the results the significant differences among FfreeF with almost no sealability of AVGAS vapours offered by the two other formulations. Presented at the Suppression and Detection Research and Applications—A Technical Working Conference (SUPDET 2007); Wyndham Orlando Resort, March 5–8, 2007, Orlando, FL, USA.     

The effect of fuel area size on behavior of fires in a reduced-scale single-track railway tunnel

A set of experiments was carried out in a 1/9 reduced-scale single-track railway tunnel to investigate the effect of fuel area size on the temperature distribution and behavior of fires in a tunnel with natural ventilation. Methanol pool fires with four different fuel areas 0.6 × 0.3 m² (1 pan), 1.2 × 0.3 m² (2 pans), 2.4 × 0.3 m² (4 pans) and 3.6 × 0.3 m² (6 pans), were used in these experiments. Data were collected on temperatures, radiative heat flux and mass loss rates. The temperature distribution and smoke layer in the tunnel, along with overflow dimensions and radiant heat at the tunnel entrance were analyzed. The results show that as the fuel area enlarges, the fire gradually becomes ventilation-controlled and the ceiling temperature over the center of fire source declines. Burning at the central region of fire source is depressed due to lack of oxygen. This makes the temperature distribution along the tunnel ceiling change from a typical inverted V-shape to an M-shape. As observed in the experiments, a jet flame appeared at tunnel entrances and both the size and temperature of the flame increased with the enlargement of fuel area leading to a great threat to firefighters and evacuees in actual tunnel fires.     

Deflagrations involving stratified heavier-than-air vapor/air mixtures

The distribution of explosion damage in a structure is a major indicator of the type of explosive material involved and its location. A solid-phase explosive material typically produces localized or “seated” damage, where a vapor/air explosive mixture typically produces generalized, omnidirectional damage. Investigators have been taught that the finding of more intense blast damage to lower portions of an enclosure indicates that the vapors were heavier than air, while explosion damage to upper portions indicates a lighter-than-air gaseous fuel. Most of the explosion pressure data in the literature deal with well-mixed mixtures that are uniform in concentration prior to ignition. This study explores the pressure distributions produced by the ignition of shallow (0.05–0.2 m deep) layers of hexane vapor created by the evaporation of liquid in a still, isothermal compartment. The floor-level vapor layers thus produced were ignited by an electric arc and the pressures at five different locations in the room were monitored. It was found that pressures increased in an exponential fashion over a period of 300–400 ms after ignition until the relief panel failed (at ∼5–6 kPa). The peak pressures observed at all five locations in the compartment coincided in time (to within ±5 ms) and intensity suggesting that the pressures produced within the 3.6 m×2.4 m×2.4 m chamber equilibrated very quickly. Any failure of the compartment, then, would be the result of failure of the weakest part of the confining structure, rather than the result of pre-ignition distribution of the fuel/air mixture. A small (∼−2 kPa), but reproducible negative pressure peak was observed some 60–70 ms after the maximum positive pressure. This finding shows that negative pressure peaks can be produced by deflagrating vapor/air mixtures that could exert physical effects on lightweight debris dislodged by the initial positive pulse.     

Sediment-adsorbed total mercury flux through Yolo Bypass,the primary floodway and wetland in the Sacramento Valley,California

The fate and transport of mercury are of critical concern in lowland floodplains and wetlands worldwide, especially those with a history of upstream mining that increases the mobility of both dissolved and sediment-bound Hg in watersheds. A mass budget of total mercury (THg) quantifies sources and storage for particular areas — knowledge that is required for understanding of management options in lowland floodplains. In order to assess contaminant risk in the largest flood-control bypass, prime wetland, and restoration target in the Sacramento River basin, we estimated empirical relationships between THg, suspended sediment concentration (SSC), and streamflow (Q) for each of the major inputs and outputs using data from various publicly available sources. These relationships were improved by incorporating statistical representations of the dynamics of seasonal and intra-flood exhaustion (hysteresis) of sediment and mercury. Using continuous records of Q to estimate SSC suspended sediment flux and SSC to estimate THg flux, we computed the net transfer of sediment-adsorbed mercury through the Yolo Bypass over a decade, 1993–2003. Flood control weirs spilling Sacramento River floodwaters into the bypass deliver ~ 75% of the water and ~ 50% of the river's suspended sediment load, while one Coast Range tributary of the bypass, Cache Creek, contributes twice the THg load of the mainstem Sacramento. Although estimated sediment flux entering Yolo Bypass is balanced by efflux to the Sacramento/San Francisco Bay-Delta, there is much evidence of deposition and remobilization of sediment in Yolo Bypass during flooding. These factors point to the importance of the bypass as sedimentary reservoir and as an evolving substrate for biogeochemical processing of heavy metals. The estimates of mercury flux suggest net deposition of ~ 500 kg in the 24,000 ha floodway over a decade, dominated by two large floods, representing a storage reservoir for this important contaminant.     

Development of titania coatings on glass foams

TiO₂ coatings on glass foam substrates were produced by electrophoretic deposition (EPD) and sol–gel method with the aim to impart surface functional properties to glass foam such as antibacterial and photocatalytic effects. Starting with charged TiO₂ nanoparticles (21 nm) suspended in acetylacetone, EPD was shown to be a useful method to obtain TiO₂ coating on the glass foam substrates placed close to the deposition electrodes in the EPD cell. Best results were obtained by applying 25 V for 4 min and a subsequent thermal treatment (450 °C for 1 h). In the second approach, multilayer sol–gel TiO₂ coatings on glass foam were fabricated, which were heat-treated at 450 °C for 1 h to obtain pure anatase structure. Both techniques led to partially microcracked coatings which were however well adhered to the glass foam substrate (qualitatively assessed). The presence of microcracks was not considered to be a disadvantage as they increase the surface area of the coating, which is required to maximise the interaction of the titania layers with the environment for their antibacterial and photocatalytic function.     

An estimate of the correction applied to radiant flame measurements due to attenuation by atmospheric CO2 and H2O

A narrow band statistical model has been used to estimate the uncertainty introduced into radiative heat flux measurements from fires which is attributable to attenuation by atmospheric H₂O and CO₂. The flames were assumed to be soot-dominated with blackbody emission characteristics. The ambient surroundings near the flames were assumed to be homogeneous with the total pressure being fixed at one atmosphere. Atmospheric CO₂ concentrations were held constant at 0.04 kPa and the water vapor concentrations varied between 0.55–5.63 kPa based on temperature and relative humidity. The remaining partial pressures were accounted for by O₂ and N₂. Correlations to estimate atmospheric attenuation are given over a range of conditions that include path length (10–200 m), ambient temperature (19–35°C), source temperature (1000–1600°C) and relative humidity (0.25–1.0) as parameters. The results of these calculations indicate that, over this range of conditions, the radiant flux can be attenuated by as much as 42%.     

Numerical study of the behaviour of a surface fire propagating through a firebreak built in a Mediterranean shrub layer

The efficiency of a firebreak, built in a shrubland has been studied numerically using a multiphase physical model. The physical mechanisms governing the propagation of the surface fire and the consequences upon the temperature signal and the radiative heat flux received by a target located at 1 m above the ground level, have been firstly studied before positioning the firebreak. The role played by the flame and the recirculation of hot gases to the ignition of unburned fuel (especially the dry grass) ahead of the fire front have been clearly identified. Four values of the firebreak width L_C (ranged between 5 and 20 m) and 3 values of wind velocities (ranged between 1 and 8 m/s) have been tested. The simulations show that above a threshold value of this parameter, even if a small amount of the fuel located on the opposite side of the firebreak was ignited, the released energy was not sufficient to sustain the propagation of the surface fire after crossing the firebreak.     

Portable gasoline container headspace flammability

This work summarizes the findings of a multi-year study into the flammability hazards associated with portable gasoline containers (PGC's). In particular, this investigation focuses on identifying the limited conditions under which a flame can propagate through the pour spout and into the PGC, causing a deflagration. The first series of tests simulate quiescent gasoline storage in a 18.9 l (5 gallon) PGC with a child resistant spout and closure. The storage conditions are varied to include a range of liquid volumes (5 to 500 mL) and temperatures (−30 to 0 °C). The second series of tests simulates pouring of gasoline from the PGC and involves testing over a range of tilt angles from 61 to 73°. In both cases, vapor concentrations are obtained from a paramagnetic oxygen analyzer and from an infrared sensor calibrated for n-butane. It is found that the container tilt angle is a significant controlling parameter and that liquid volumes ranging from 5 to 30 mL in a 18.9 l PGC are capable of producing a flammable headspace region. Finally, a model is developed to predict the influence of these controlling parameters on the flammability hazard.     

Improved parameterization of dust emission (PM10) fluxes by the gradient method using the Naiman tower data at the Horqin desert in China

Dust emission/deposition flux has been estimated using the gradient method with the two-level (3 and 15 m high) measured PM₁₀ concentrations and the sonic anemometer measured momentum and kinematic heat fluxes at 8 m high from a 20-m monitoring tower located at Naiman (Horqin desert) in the Asian dust source region in China for the winter of November 2007 to March 2008. The time series of measured PM₁₀ concentration at 3 m high is used to identify the dust event and the non-dust event periods. It is found that the dust emission/deposition flux (F_C) shows a significant diurnal variation with the maximum emission flux of 5.8 kg km^? 2 h^? 1 at noon and the minimum of ? 1.6 kg km^? 2 h^? 1 in the afternoon for the non-dust event cases. Whereas for the dust event cases, the dust emission flux is found to occur when the prevailing winds are westerlies to northerlies with the maximum flux of 1275 kg km^? 2 d^? 1, while the maximum dust deposition flux of 148 kg km^? 2 d^? 1 occurs with the prevailing winds of southerlies to easterlies without any diurnal variation. The optimal regression equation between F_C and the friction velocity (u_*) for the dust emission cases is found to be F_C = 9.55 u_*^3.13 with the R² value of 0.73. However, this regression equation can be improved by taking into account the convective velocity (w_*). The resulting optimal regression equation is found to be F_C = 9.3(u_* ? 0.1w_*)^3.19 for the stable stratification (w_* < 0) with the R² value of 0.77 and F_C = 10.5(u_* + 0.34w_*)^4.11 for the unstable stratification (w_* > 0) with the R² value of 0.78, suggesting the importance of the convective velocity on the dust emission flux.     

Thermal analysis of wood-based test cells

The objective of the present paper is to evaluate the thermal performance of diverse wood-based panels in small-scale test cells of 1 m × 1 m × 1 m of internal volume. The thermal evaluations took place under the climatic conditions of Curitiba, Brazil (latitude 25.5°S, elevation 917 m above sea level), which is characterized by a subtropical climate with high daily and annual amplitudes of the air temperature. The research comprised of the following steps: (1) heat flux measurements through each panel configuration; (2) indoor temperature measurements under summer and winter climatic conditions. Reference material for indoor temperature comparisons was a prototype made with ordinary ceramic bricks, plastered on both sides. Air temperature measurements were carried out with data-loggers, heat flux plates were attached to an exposed north facade of each test cell, while incoming solar radiation was measured with an experimental solarimeter.     

Buttock responses to contact with finishing materials over the ONDOL floor heating system in Korea

The ONDOL is a conventional floor heating system in Korea. Eight healthy college students volunteered as the subjects to investigate the buttock responses to contact with 10 types of the ONDOL covering materials: mortar, plywood, artificial marble, PVC, rubber foam, tempered glass, steel, insulation mortar, carpet, and aluminum. The temperature of water supply flowing into the floor coil underneath the floor surface was altered from 15 to 40 °C at 5 °C intervals. Floor surface temperature, skin temperature including buttock and subjective thermal sensation were monitored. The study revealed that the lower the contact coefficient of covering material, the more stable the temperature fluctuations in the floor surface and the buttock skin were. The floor finishing material should be chosen by the heat flux based on the heating load, and the friendship to human body. Using regression analysis, the neutral temperature of the buttock was determined at 32.6 °C.     

水成膜泡沫在航空煤油表面的封闭性效果

采用不同环境温度、不同混合比对水成膜泡沫在燃油液面的覆盖开展了封闭性验证实验,通过测定可燃蒸气的浓度及检测时间分析了水成膜泡沫的封闭性随环境温度、混合比的变化规律.实验结果表明:水成膜泡沫的封闭性随环境温度的升高而变差,对于3％的水成膜泡沫,环境温度为40℃时的初次检测可燃蒸气的时间比80℃时的检测时间延长149 s;...     

Fracture behavior of framing coated glass curtain walls under fire conditions

Breaking glass and its subsequent fallout may markedly affect enclosure fire dynamics. However, little is known about the thermal fracture behavior of framing glass façades in different installation forms. Sixteen 600×600×6 mm³ solar control coated glass panes, installed in exposed, semi-exposed and hidden frames, were heated by a 500×500 mm² n-heptane pool fire to investigate the influence of frame constraints on glass breakage and fallout. Measurements were taken of the time to breakage occurrence, heat release rates, incident heat flux, central gas temperatures and glass surface temperatures. Measurements in relation to crack initiation and propagation as well as loss of integrity of the glazing assembly were also recorded. The experimental results show that all cracks initiated at the edge of covered sections and intersected rapidly, forming islands. The maximum temperature difference and heat flux that the glass can withstand are primarily in the range of 50–90 °C and 9–15 kW/m². Using the finite element method (FEM), the breakage mechanism is demonstrated, the predictions of which are in reasonably good agreement with the experimental results. Among four different installation forms, semi-exposed framing façades showed better fire resistance than exposed framing façades. Meanwhile, the fire resistance of hidden framing façades may depend on the fire location. It is intended that these results will provide practical guidelines for fire safety design.     

Experimental study and implementation of a novel internal foam spraying system for roadheaders

Foam technology utilizes the good coverage of foam to form a closed space around dust sources. The foam then wets the dust particles, causing them to adhere before they spread into the air, resulting in better dust control than with water sprays. In the process of foam dust control at a heading face, the foam spray trajectory is highly influenced by the wind, making it difficult to focus foam on the dust sources, which wastes the foam and reduces dust control efficiency. To resolve this problem, the idea of transporting foam to the cutting head through the roadheader’s inner pipeline is proposed. To adapt to the high resistance of foam delivery in the roadheader’s inner pipeline, according to the water and air supply of the heading face, a table water-jet suction device and porous spiral coupling foaming device were designed, and the working conditions were tested using a self-designed experiment system in the laboratory. The results showed that the foaming agent could be automatically added into the device at a working water flow rate of 1–1.6 m³/h at a ratio of 1%. The optimum air flow was 45–50 m³/h, in which range the foam expansion ratio reached the maximum and the outlet pressure demand was satisfied. Field application showed that the new foam method had a better dust control efficiencies than traditional foam methods.     

Granulated foam glass–ceramic material from zeolitic rocks

The objective of this research work was to investigate the production of granulated foam glass–ceramic material from zeolitic rocks. The investigations have shown that grinding raw materials to particle size less than 0.5 mm and adding 13.8% of alkali content provide production of material with the following properties: particle density – 340 kg/m³, strength – 1.6 MPa and water adsorption – 13% at firing temperature of 850 °C. Expanded zeolite with alkali content is a material of glass–ceramic composition with amorphous part of 38.6% and crystalline part of 61.4% that gives higher strength in comparison with sponge glass.     

Time-dependent smoke yield and mass loss of pool fires in a reduced-scale mechanically ventilated compartment

Technical and pure grades of the combustibles heptane and dodecane were used in a series of small-scale fire tests conducted in a 1 m³ compartment that was mechanically ventilated at 5 and 8 air changes per hour (ACH). Combustible mass loss rates, soot mass concentrations, soot size distributions, several gas species concentrations, and compartment temperatures were measured during the fire. Results for the two pure-grade hydrocarbons were compared with results obtained for their respective technical grades. Technical-grade dodecane produced the highest soot emissions; pure n-heptane produced the lowest. Soot size distributions of all four combustibles attained a steady profile whose modal diameter was about 200 nm. Underventilated fires showed higher carbon monoxide yields than soot yields. Both compartment ventilation rates produced similar results, although the fire self-extinguished earlier for 5 ACH.     

Development and characterization of an inorganic foam obtained by using sodium bicarbonate as a gas generator

In the construction industry almost all of the insulating and expansive materials are organic foams. In this work, the production of an inorganic foam is described. Sodium bicarbonate is used as a gas generator. CO₂ gas is released when water is added to the mixture of sodium bicarbonate and β-hemihydrate gypsum powder (CaSO₄ · 1/2H₂O). Hence, stabilization of the foam is achieved when CO₂ gas is released and water is absorbed by β-hemihydrate gypsum powder, which subsequently is converted into calcium sulphate dihydrate (gypsum matrix). The bulk density and mechanical properties (compressive and flexural strength) of the inorganic foam and gypsum were determined. Microstructural characterization has been carried out by SEM and XRD, and a new sodium sulphate phase was identified in the gypsum foam due to this chemical reaction. Finally, thermal properties such as thermal conductivity and diffusivity were measured and it was observed how for the same heat flux, the thickness of an inorganic foam slab is 73.4% less than that of a concrete slab.     

Effectiveness of vertical barriers in preventing lateral flame spread over exposed EPS insulation wall

Insulation panels made of organic, combustible materials are frequently used in the exterior thermal insulation systems (ETIS) for buildings. Such combustible insulation panels have been involved in several catastrophic building fires in recent years in China. One potential strategy to mitigate this fire hazard is to limit fire spread over the ETIS. The present work evaluates the effectiveness of vertical fire barriers in inhibiting fire spread over exposed insulation walls made of expanded polystyrene (EPS) panels. Reduced-scale experiments were carried out indoors using EPS panels with or without two vertical barriers made of non-combustible mineral wool, the fire started at the bottom center of the middle panel. The interval and width of the barriers were varied systematically, while the temperature distribution on the wall, the radiation heat flux from the fire, and the infra-red (IR) images were recorded. To demonstrate the validity of the concept, an outdoor, full-scale experiment was carried out using a 7-floor building. Our reduced-scale experiments showed that the installation of two vertical fire barriers successfully stopped the lateral flame spread, decreasing the peak temperatures of the two side panels by about 300 °C for all barrier configurations tested. When barrier width was fixed at 5 cm, an increase of the barrier interval from 30 to 90 cm led to increases in the peak temperatures, radiation heat flux, and the maximum rate of upward flame spread. By contrast, when barrier interval was fixed at 90 cm, an increase of the barrier width from 2 to 5 cm had little influence on the combustion dynamics of the middle panel but the peak temperature on the side panels dropped, consistent with the smaller heat transferred with wider fire barriers. In the regions of the side panels next to the barriers, pyrolysis and deformation could be observed with barrier widths of 2 and 3 cm, but not 5 cm. Finally, our outdoor, full-scale experiment demonstrated that a 30 cm wide vertical barrier made of air-filled cement successfully stopped the lateral flame spread over exposed EPS wall. The study highlights the effectiveness of vertical fire barriers in preventing the lateral flame spread over the exposed EPS insulation wall and provides another option for enhancing the fire safety of the combustible insulation systems.