Search Results (123)

Compression–ignition engines emit particulate matter (PM) (soot), prompting the widespread use of diesel particulate filters (DPFs) in the automotive sector. An alternative method for PM reduction involves the use of ultrasonic waves to disperse and modify the structure of exhaust particles. This article presents experimental results of the effects of ultrasonic emitter parameters, including the number, arrangement, and power, along with the engine speed, on the exhaust smoke density. Tests were conducted on a laboratory prototype equipped with six ultrasonic emitters spaced 0.17 m apart. The exhaust source was a diesel engine from a construction excavator, based on the MTZ-80 tractor design, delivering 80 HP and a displacement of 4750 cm³. A regression model was developed to describe the relationship between the engine speed, emitter power and spacing, and smoke density. The optimal configuration was found to involve an emitter power of 319.35 W and a spacing of 1.361 m for a given engine speed. Under the most effective conditions—an engine speed of 1500 rpm, six active emitters, and a total power of 600 W—smoke emissions were reduced by 18%. These findings support the feasibility of using ultrasonic methods as complementary or alternative exhaust gas filtration techniques for non-road diesel engines. Full article

This study presents a novel water mist fire fighting system that integrates water mist sprays and water mist curtains, designed to achieve simultaneous fire suppression, thermal insulation, and smoke control. Three full-scale experiments were conducted under various fire scenarios, and the changes in fire behavior and heat release rate were examined to evaluate the effectiveness of the water mist system in extinguishing fires. Additionally, the spatiotemporal changes in ceiling temperature were monitored to assess the cooling and protective effects of the water mist. The thermal insulation capability of the system was also investigated by detecting the temperature distribution inside the tunnel. Moreover, the smoke conditions upstream and downstream of the tunnel were analyzed to evaluate the smoke-blocking performance of the water mist system. The findings demonstrate that the water mist fire fighting system is highly efficient in attenuating the fire and restricting its progression. Within the water mist spray section, the average ceiling temperature decreased exponentially during both the initial and steady burning phases across all tested fire scenarios. Nonetheless, the smoke-carrying capacity of the water mist spray is limited. Fortunately, the dispersed smoke was diluted by water mist, markedly enhancing visibility and mitigating the impact of smoke on tunnel illumination. Full article

Current research on fires in high-speed train carriages mainly focuses on the temperature distribution of smoke, while the flow structure and dynamic evolution patterns of smoke have not been reviewed. This study employs numerical simulation to systematically investigate the fire ejection behavior from broken windows of a high-speed train carriage, and the influence of different broken window parameters was considered. The research results indicate that the asymmetric geometric configuration of seats on both sides of the fire source induces a lateral displacement of fire smoke toward the downstream direction due to the sidewall effect, resulting in an asymmetrical distribution of smoke flow velocity and temperature within the compartment. Compared to fire scenarios with one broken window, the presence of broken windows on both sides increases the number of smoke dispersion outlets, leading to a significant rise in smoke flow velocity around the fire source. In the aisle region far from the fire source, the smoke flow velocity decreases, consequently lowering the compartment temperature. Compared with the case of one broken window, the aisle temperature decreased by 83 K in the case of two broken windows. When the broken window is located farther from the fire source, smoke tends to accumulate extensively within the compartment before being discharged through the broken windows, which enhances the longitudinal smoke flow velocity and elevates the compartment temperature. When a window far from the fire source is breached, the temperature in the aisle increases by 270 K compared to when a window in the middle of the carriage is breached. Full article

The prevailing fire-resistant design of steel structures typically relies on the premise of localized heating, whereas the overall temperature increase resulting from the dispersion of hot smoke is frequently oversimplified. These theoretical simplifications may result in considerable structural safety risks. This research utilized the Transient Thermo-Mechanical Coupling Theory and developed a double-layer steel frame finite element model using ABAQUS 2023 software. The simulation of multi-physics field coupling involving smoke convection-radiation heat transfer and nonlinear structure response in fire situations was accomplished by establishing 24 sets of comparative conditions over three distinct premises. Upon comparing the conditions with the greatest displacement values across the three situations, it was concluded that when hot smoke is produced in the initial room, it commences diffusion into adjacent rooms both horizontally and vertically. In comparison to the scenario that disregards the dispersion of hot smoke, the displacement of the components escalated by 342.3%. The dispersion of hot smoke reveals that the displacement of components in the center room of the fire’s origin was 23.1% greater than in the corner room, while the displacement in the second-story room was 115.6% greater than in the first-story room. The use of fireproof coating markedly diminished component displacement in the context of hot smoke dispersion, achieving an 82.8% reduction in displacement among components in identical positions. The enhanced vulnerability model augmented the precision of forecasting the ongoing failure of steel frames by 29.1%. Full article

Beta attenuation monitors (BAMs) are widely used for the regulatory monitoring of fine particulate matter (PM_2.5) and fence line monitoring of industrial sites. The elemental analysis of BAM filter tapes potentially could enable additional source PM_2.5 attribution. However, the chemical characterization of the glass fiber filters is hindered by high background metal values. A sample preparation method was developed using the ultrasonic extraction of particulate matter from BAM filter spots in nitric acid and the analysis of metals by inductively coupled plasma–mass spectrometry (ICP-MS) and scanning electron microscopy–energy-dispersive X-ray spectroscopy (SEM-EDS). To demonstrate the utility of this method, BAM filter spots were analyzed from wildfire smoke periods in the San Francisco Bay Area in California in Fall 2023 and indicated elevated levels of chromium compared to a non-wildfire period in Spring 2023. The SEM-EDS of the BAM tape was used to probe individual particulate morphology, but it only detected Fe and Ba at levels above the blank media. The ultrasonic extraction method of BAM filter spots could be used in future wildfire smoke events to extend the characterization of beta attenuation monitor filters in PM_2.5 monitoring. Full article

Aluminum hydroxide (ATH) is an environmentally friendly flame retardant widely employed in polymers. However, the high loading of ATH, due to its limited efficiency, potentially compromises other properties, including mechanical properties. This work explores a feasible ball milling strategy for high-efficiency ATH-based flame retardants (PPA-ATH and PPOA-ATH), fabricated by employing phenylphosphinic acid (PPA) and phenylphosphonic acid (PPOA) as surface modifiers and water as the processing solvent. The characterization study of PPA-ATH and PPOA-ATH demonstrates that ball milling effectively reduces their particle size, enhances their specific surface area, and improves their dispersibility within the ethylene-vinyl acetate (EVA) matrix. PPOA-ATH exhibited superior capabilities in enhancing the thermal stability and flame retardancy of EVA composites compared to PPA-ATH. The incorporation of PPOA-ATH resulted in the retarding in the temperature at 50% mass loss by 21 °C and an increase in the char residue of 34.5% at 700 °C. Furthermore, PPOA incorporation led to reductions of 81.0% in the peak heat release rate, 48.1% in the total heat release, 73.7% in the peak smoke production rate, and 41.2% in the total smoke production compared to neat EVA. This green modification strategy successfully addresses the application limitations of ATH, providing a feasible and environmentally friendly method for high-efficiency ATH-based flame retardant fabrication. Full article

A subway transfer station hall is crowded and complex in structure, which makes evacuation more difficult in case of a fire, but also provides more strategic options for smoke extraction. Full-scale experiments and numerical simulations are conducted to investigate the feasibility and performance of coordinated ventilation in a T-shaped transfer station hall, accounting for different fire source locations, ventilation modes, and fire shutter operations. It is found that the optimal ventilation strategy varies based on the fire location within the T-shaped configuration. For fires on the ‘T’s horizontal side, lateral airflow from longitudinal fans can effectively disrupt smoke spreading, with coordinated extraction strategies outperforming the traditional methods. However, for fires on the ‘T’s longitudinal side, horizontal fans are ineffective in controlling smoke flow, making the traditional fire shutter closure optimal. The idea of dispersing hot smoke to a reasonable degree can create better evacuation conditions for people near a fire, while creating almost no new danger zones. Full article

Background: Aortic valve calcification results from degenerative processes associated with several pathologies. These processes are influenced by age, chronic inflammation, and high concentrations of phosphate ions in the plasma, which contribute to induce mineralization in the aortic valve and deterioration of cardiovascular health. Environmental factors, such as wood smoke that emits harmful and carcinogenic pollutants, carbon monoxide (CO), and nitrogen oxide (NO_x), as well as other reactive compounds may also be implicated. The purpose of this research was to study the impact of wood smoke on specific aortic valve characteristics, including lesion size and percentage of mineralization, in patients with aortic valve stenosis (AS). Methods: This observational study included 65 patients who underwent primary valve replacement surgery at the National Institute of Cardiology, 11 of whom were exposed to wood smoke. For each patient, approximately 0.5 cm of aortic valve tissue was collected along with a blood sample anticoagulated with sodium citrate. The valves were analyzed using scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM–EDS). Since extracellular microvesicles (MVs) may induce epigenetic changes in target cells by transferring their cargo, we also analyzed their mineral content. Results: Individuals exposed to wood smoke exhibit more extensive lesion (835 µm²) characteristics compared to those with no exposure (407.5 µm²). Interestingly, FESEM images of MVs showed the presence of minerals on their surface, thus providing evidence on their possible role in the pathophysiology of mineralization. Conclusions: Our study uniquely demonstrates imaging-based evidence of structural damage and mineralization in aortic valve tissue, with chronic wood smoke exposure emerging as a significant causative factor. Full article

In this study, a sustainable cellulose-based flame-retardant additive was developed, characterized, and incorporated into polypropylene (PP). Microcrystalline cellulose (Cel) was chemically modified with P₂O₅ using the solvent-free ball-milling mechanochemistry approach at room temperature. This modification enabled phosphorus grafting onto cellulose, significantly enhancing the cellulose charring ability and improving the thermal stability of the char as revealed by thermogravimetric analysis (TGA). The resulting product, Cel-P, containing 4.15 wt.% phosphorus, was incorporated and uniformly dispersed as a flame-retardant (FR) additive at 30 wt.% in PP through melt processing. The PP+30-Cel-P composite demonstrated improved char formation and FR properties, including reduction of both peak heat release rate (pHRR) and total heat release (THR) in mass loss cone calorimetry (MLC). Moreover, lower light absorptivity was obtained by smoke opacity tests as compared to PP filled with unmodified cellulose. Full article

In previous studies on tunnel fires, researchers primarily focus on the impact of a single factor on smoke dispersion characteristics in tunnels, neglecting the combined effects of multiple influencing factors and their mutual interactions. Based the theory of smoke dispersion, a series of numerical simulations were performed using a fire dynamics simulator to reveal smoke distribution characteristics in mountain spiral highway tunnels. The results indicated that the radius of curvature, altitude, and slope gradient predominantly govern tunnel fire distribution in spiral tunnels. Specifically, the impact of the radius of curvature on smoke dispersion patterns is independent, whereas altitude and slope gradient exhibit interactive effects. Notably, increased altitude intensifies the chimney effect induced by a slope due to faster smoke dispersion in tunnels with higher altitude. Conversely, an enlarged slope mitigates the thickening of the smoke layer caused by the altitude, as it reduces the layer thickness in tunnels with steeper slopes. The results can play a role for further elucidating the numerical smoke distribution patterns in spiral tunnels. Full article

To enhance the fire safety performance in polystyrene (PS), a novel organic–inorganic hybrid material (FGO–AHP) was successfully prepared by the combination of functionalized graphene oxide (FGO) and aluminum hypophosphite (AHP) via a chemical deposition method. The resulting FGO–AHP nanohybrids were incorporated into PS via a masterbatch-melt blending to produce PS/FGO–AHP nanocomposites. Scanning electron microscope images confirm the homogeneous dispersion and exfoliation state of FGO–AHP in the PS matrix. Incorporating FGO–AHP significantly improves the thermal behavior and fire safety performance of PS. By incorporating 5 wt% FGO–AHP, the maximum mass loss rate (MMLR) in air, total heat release (THR), and maximum smoke density value (D_smax) of PS nanocomposite achieve a reduction of 53.1%, 23.4%, and 50.9%, respectively, as compared to the pure PS. In addition, thermogravimetry–Fourier transform infrared (TG–FTIR) results indicate that introducing FGO–AHP notably inhibits the evolution of volatile products from PS decomposition. Further, scanning electron microscopy (SEM), FTIR, and Raman spectroscopy were employed to investigate the char residue of PS nanocomposite samples, elaborating the flame-retardant mechanism in PS/FGO–AHP nanocomposites. Full article

At the end of the dry season, from early March to early April each year, extensive agricultural biomass waste burnings occur throughout insular mainland Southeast Asia. During this biomass-burning period, smoke aerosols blanketed the whole region and were transported and dispersed by predominant westerly and southwesterly winds to southern China, Taiwan, and as far southern Japan and the Philippines. The extensive and intense burnings coincided with some wildfires in the forests due to high temperatures, making the region one of the global hot spots of biomass fires. In this study, we focus on the effect of pollutants emitted from biomass burnings in March 2019 at the height of the burning period on the exposed population and their health impact. The Weather Research Forecast-Chemistry (WRF-Chem) model was used to predict the PM_2.5 concentration over the simulating domain, and health impacts were then assessed on the exposed population in the four countries of Southeast Asia, namely Thailand, Laos, Cambodia, and Vietnam. Using the health impact based on log-linear concentration-response function and Integrated Exposure Response (IER), the results show that at the peak period of the burnings from 13 to 20 March 2019, Thailand experienced the highest impact, with an estimated 2170 premature deaths. Laos, Vietnam, and Cambodia followed, with estimated mortalities of 277, 565, and 315 deaths, respectively. However, when considering the impact per head of population, Laos exhibited the highest impact, followed by Thailand, Cambodia, and Vietnam. The results highlight the significant health impact of agricultural waste burnings in Southeast Asia at the end of the dry season. Hence, policymakers should take these into account to design measures to reduce the negative impact of widespread burnings on the exposed population in the region. Full article

Phospholipids are the main building components of cell membranes and are also used for cell signaling and as energy storages. Cancer cells alter their lipid metabolism, which ultimately leads to an increase in phospholipids in cancer tissue. Surgical energy instruments use electrical or vibrational energy to heat tissues, which causes intra- and extracellular water to expand rapidly and degrade cell structures, bursting the cells, which causes the formation of a tissue aerosol or smoke depending on the amount of energy used. This gas phase analyte can then be analyzed via gas analysis methods. Differential mobility spectrometry (DMS) is a method that can be used to differentiate malignant tissue from benign tissues in real time via the analysis of surgical smoke produced by energy instruments. Previously, the DMS identification of cancer tissue was based on a ‘black box method’ by differentiating the 2D dispersion plots of samples. This study sets out to find datapoints from the DMS dispersion plots that represent relevant target molecules. We studied the ability of DMS to differentiate three subclasses of phospholipids (phosphatidylcholine, phosphatidylinositol, and phosphatidylethanolamine) from a control sample using a bovine skeletal muscle matrix with a 5 mg addition of each phospholipid subclass to the sample matrix. We trained binary classifiers using linear discriminant analysis (LDA) and support vector machines (SVM) for sample classification. We were able to identify phosphatidylcholine, -inositol, and -ethanolamine with SVM binary classification accuracies of 91%, 73%, and 66% and with LDA binary classification accuracies of 82%, 74%, and 72%, respectively. Phosphatidylcholine was detected with a reliable classification accuracy, but ion separation setups should be adjusted in future studies to reliably detect other relevant phospholipids such as phosphatidylinositol and phosphatidylethanolamine and improve DMS as a microanalysis method and identify other phospholipids relevant to cancer tissue. Full article

Asymmetrical V-shaped tunnels often appear in tunnels crossing the river or urban underground road tunnels. The smoke flow inside is affected by a lot of factors. A full understanding of the smoke flow in this kind of tunnel is the basis of the smoke control. In this study, the effects of slope composition and fire heat release rate (HRR) on the longitudinal induced airflow velocity, the smoke back-layering length at the small slope side, and the maximum ceiling temperature were studied by the numerical method. The results show that when the fire occurs at the slope change point of the V-shaped tunnel, the maximum ceiling temperature decreases with the increase in the slope of the large-slope side tunnel. The longitudinally induced velocity is primarily related to the slope of the large-slope side tunnel and the fire HRR. When the slope difference between the side tunnels or the slope of the large-slope side tunnel is large, the smoke in the small-slope side tunnel flows back toward the fire source after reaching its maximum dispersion distance and then reaches a quasi-steady state. The smoke back-layering length is mainly affected by the slope and length of the large-slope side tunnel. When the slope of the large-slope side tunnel is 9%, the induced airflow velocity from the small-slope side can prevent the spread of smoke. The empirical models of the smoke back-layering length and the longitudinal induced airflow velocity in the small-slope side tunnel are drawn, respectively, by the theoretical analysis and the numerical results. This study can provide technical support for the design and operation of smoke control systems in V-shaped tunnels. Full article

The frequency of extreme wildfire events (EWEs) is expected to increase due to climate change, leading to higher levels of atmospheric pollutants being released into the air, which could cause significant short-term impacts on human health (both for the population and firefighters) and on visibility. This study aims to gain a better understanding of the effects of EWEs’ smoke on air quality, its short-term impacts on human health, and how it reduces visibility by applying a modelling system to the Portuguese EWEs of October 2017. The Weather Research and Forecasting Model was combined with a semi-empirical fire spread algorithm (WRF-SFIRE) to simulate particulate matter smoke dispersion and assess its impacts based on up-to-date numerical approaches. Hourly simulated particulate matter values were compared to hourly monitored values, and the WRF-SFIRE system demonstrated accuracy consistent with previous studies, with a correlation coefficient ranging from 0.30 to 0.76 and an RMSE varying between 215 µg/m³ and 418 µg/m³. The estimated daily particle concentration levels exceeded the European air quality limit value, indicating a potential strong impact on human health. Health indicators related to exposure to particles were estimated, and their spatial distribution showed that the highest number of hospital admissions (>300) during the EWE, which occurred downwind of the fire perimeters, were due to the combined effect of high smoke pollution levels and population density. Visibility reached its worst level at night, when dispersion conditions were poorest, with the entire central and northern regions registering poor visibility levels (with a visual range of less than 2 km). This study emphasises the use of numerical models to predict, with high spatial and temporal resolutions, the population that may be exposed to dangerous levels of air pollution caused by ongoing wildfires. It offers valuable information to the public, civil protection agencies, and health organisations to assist in lessening the impact of wildfires on society. Full article