Hot Smoke Research Articles

Alendronate-Modified Nanoceria with Multiantioxidant Enzyme-Mimetic Activity for Reactive Oxygen Species/Reactive Nitrogen Species Scavenging from Cigarette Smoke.

Highly toxic radicals including reactive oxygen species (ROS) and reactive nitrogen species (RNS) in cigarette smoke play an important role in oxidative damage of the lungs, which cannot be efficiently scavenged by current filter techniques. Herein, a novel alendronate-coated nanoceria (CeAL) nanozyme is explored for cigarette filter modification for ROS/RNS scavenging. The CeAL nanozyme with an adjustable oxidation state and high thermal stability exhibits an excellent superoxide dismutase (SOD)-like activity, hydroxyl radical elimination capacity, catalase-mimicking activity, and nitric oxide radical scavenging ability. These synergistic antioxidant abilities make the CeAL nanozyme a lucrative additive for cigarette filters. The filter incorporated with the CeAL nanozyme can efficiently scavenge ROS/RNS in the hot smoke generated by burned commercial cigarettes, resulting in reduction of oxidative stress-induced pulmonary injury and acute inflammation of mice. The developed CeAL nanozyme opens up new opportunities for cigarette filter modification to decrease the toxicity of cigarette smoke and expands the application fields of nanoceria.

Numerical Simulations on the Extinguishing Effect of Water Mist System with Different Parameters of Longitudinal Ventilation in Curve Tunnel Fire

Once a fire occurs in a long curve tunnel, the mixing of hot smoke flow and cold air leads to turbulence due to the curvature’s impact. This phenomenon results in a greater thermal pressure difference at the fire source and a substantially greater temperature field than in the straight tunnel. The longitudinal air flowing along the wall loses a lot of velocity in the curve tunnel due to the massive wall friction. Under the same fire extinguishing conditions, the curve tunnel and straight tunnel have different requirements for longitudinal ventilation. Factors such as tunnel curvature, longitudinal ventilation operation time, and ventilation velocity were all evaluated in order to investigate the influence of longitudinal ventilation parameters on the fire extinguishing effect of water mist in the curve tunnel. The fire extinguishing effect of water mist coupling with longitudinal ventilation in the curve tunnel is studied by numerical simulation, and the recommended values of ventilation operation time and ventilation velocity in the curve tunnel with the participation of the water mist system are given. The results show that (1) the fire extinguishing effect of water mist decreases with the increase of curvature under longitudinal ventilation and (2) fire prevention effect is best when water mist and longitudinal ventilation are used in the curved tunnel, and the ventilation velocity should be greater than 2 m/s.

Experimental study on temperature profile in long-narrow compartment fire with multiple lateral openings

The openings of a compartment under fire condition are very important to exhaust the hot smoke. However, the related impacts on the indoor environment are still not clear so far to guide future designs. Experiments were then conducted using a model long-narrow compartment with multiple lateral openings. The temperature inside the compartment and the temperature profile underneath the ceiling were investigated and compared with the predict ions of those previous models. Experimental results show that the lateral opening conditions mainly affect the temperature near the fire source, and this effect does not follow a single pattern with the change of the number of lateral openings. Keeping the openings near the fire source closed and symmetrically opening the openings away from the fire source can expand the fire hazard, while asymmetrically opening the openings on the side of the fire source can effectively reduce the temperature caused by the fire. The classic models for predicting the maximum temperature rise based on the confined space with open ends underestimate the experimental data in this work. An empirical model considering various fire sizes was developed to predict the temperature decay profile underneath the ceiling. The critical dimensionless distance and the attenuation index of the attenuation zone are both related to the convective heat release rate, showing power and linear functions, respectively. These findings and results can provide reference for the fire risk assessment of a long-narrow compartment with multiple lateral openings.

Design of a small wheel-foot hybrid firefighting robot for infrared visual fire recognition

The complex and changeable environment and the different degrees of toxic hot smoke and unknown danger at fire scenes can seriously affect the fire personnel’s reconnaissance, fighting, and life safety. To address these challenges, in this study, we developed a small wheel-foot hybrid firefighting robot based on an infrared vision fire recognition system. The robot mainly involves a mechanical system, walking system, fire extinguishing system, and control system. First, the whole system and each individual system were designed and analyzed, and the visual recognition system was developed to test the recognition rate. Second, the kinematics method was used to calculate the position coordinates of the robot’s gait, and dynamic analysis of the robot’s gait process was performed. Finally, the climbing ability of the prototype model of the gait walking device was tested. The experiments showed that the average recognition rate of the flame recognition algorithm was 97.8%, and the overall detection effect was good. The robot had good terrain adaptability, and its gait uplift and forward displacement met the requirements of complex terrain conditions, such as climbing stairs. The climbing efficiency was proportional to the angular speed of the motor within a certain range.

Relationship between Designed Fire and Performance of Smoke-Control System in a Living Room

The effects of the size of a designed fire on the ventilation system of an adjacent zone is estimated in this study based on a visibility requirement of 5 m in a non-fire zone at 600 s after ignition. To verify the adequacy of the fire dynamics simulator (FDS) input file, smoke movement and ceiling temperature under the hot smoke test conditions of AS4391-1999 were compared with those from the FDS results. The average temperatures measured at 12 locations were within the range of ± 2σ, with the exception of one point, and predicted smoke movement adequately. The size of the designed fire was analyzed in terms of the air volume conditions of the NFSC 501 for a heat release rate (HRR) of 1650 kW (air supply and exhaust at 45,000 cubic meters per hour (CMH)) as well as air volume conditions for a HRR of 1100 kW (air supply at 35,606 CMH and exhaust at 32,506 CMH). It was determined that one of the major factors influencing the required safety egress time was the mixture of downdraft airflow from the diffusers and smoke layer crossing the ventilation boundary.

Experimental studies on the smoke extraction performance by different types of ventilation shafts in extra-long road tunnel fires

Ventilation shafts are widely applied in extra-long road tunnels. Experiments were conducted in a 1/20 scale model tunnel to investigate the smoke extraction performance with a ventilation shaft. Four types of shafts were compared under the normal ventilation mode and the smoke extraction mode. The influence of shaft types, the operation frequency of the jet fan and board locations were investigated. Results indicate that the smoke extraction capacity of the mechanical ventilation shaft (MTS) is almost the same as the operation frequency increases, but the smoke extraction efficiency declines as the operation frequency increases. Besides, it can be found that the smoke extraction capacity and the smoke extraction efficiency of the mechanical board-coupled shaft (MBCS) decrease as the operation frequency increases. Moreover, it was found that the smoke extraction performance of the MBCS is highly affected by the distance between the board and the shaft. And the optimal board location for the MBCS changes with the operation frequency. Furthermore, the coupling-effect of the momentum induced by the mechanical ventilation and the buoyancy induced by the hot smoke in the ventilation shaft during a fire was explored. And the dimensionless smoke extraction Froude number (Frs), was developed for characterizing the buoyancy-momentum transition during the smoke extraction process with the mechanical ventilation shaft. These studies may contribute positive significance in the smoke control and extraction design with extra-long road tunnels.

Investigation on temperature distribution under the coupling action of transverse position and fire sealing of linear fire in tunnel

By sealing the portal at one end of tunnel and changing the transverse location of linear fire source in tunnel, the hot smoke layer, longitudinal temperature distribution and maximum temperature of linear fire source were investigated. It is found that the flame will bend under the influence of curved ceiling and hot smoke layer will be thicker when the linear fire source approaches to the side wall. The variation law of heat release rate is analyzed by considering the limiting effect of side wall and thermal feedback. By modifying the previous formula of effective ceiling height, an empirical formula for predicting longitudinal temperature distribution of linear fire sources with different aspect ratios is proposed, and the ventilation coefficient is obtained to characterized the temperature under sealing and without sealing. Moreover, the accuracy of predicted temperature under sealing is verified by using the ventilation coefficient. Based on dimensional analysis, it's concluded that the maximum temperature mainly depends on the heat release rate, and an empirical formula is proposed to predict the maximum temperature rise of linear fire sources with different aspect ratios in several transverse positions. The error of predicted values and actual values is within 13%.

The combined effect of a water mist system and longitudinal ventilation on the fire and smoke dynamics in a tunnel

The individual and combined effect of a water mist system (WMS) and longitudinal ventilation (LV) on the fire HRR, smoke temperature and back-layering (BL) degree were explored in a 3 m (width)×2.2 m(height)×30 m (length) tunnel model. A series of 39 tests has been conducted in 6 configurations, varying the velocity, water volume flow rate and nozzles arrangement. When the WMS or LV is imposed individually, the reduction effect on the HRR gets stronger with larger water volume flow rates or higher velocities. Yet, under the combined effect, the effect of the LV velocity on the HRR is non-monotonic: the HRR first reduces more, and then rises again with higher LV velocities for given WMS settings. The reduction in temperature monotonically increases with higher LV velocities, in contrast to the HRR behavior. The above phenomenon is explained to be due to the relatively ‘low’ flame height in the present paper, as a consequence of which the interaction between the flame and the water droplets mainly occurs in the lower part of the tunnel, while the interaction between the hot smoke and the water droplets mainly happens in the upper part. The fire HRR behavior mainly relates to the interaction in the lower part, while the temperature depends on both regions. Besides, for a certain BL distance, the required ventilation velocities reduce by 13%–55% with activated WMS, compared to the same conditions without WMS. The effect of covering the fire with a shield is also discussed. For relatively small velocities, the fire HRR, smoke temperature and BL distance are larger with the shield in place.

Improved Hot Smoke Processing of Chub Mackerel (Scomber japonicus) Promotes Sensorial, Physicochemical and Microbiological Characteristics

Chub mackerel (CM), Scomber japonicus, is a commercially important fish species in pacific countries including South Korea and its rapid quality deterioration by various spoilage mechanisms while marketed has been reported, leading to a dramatic decline of the market price. To overcome this problem, a combination of superheated steam roasting (270 °C for 4 min) and hot smoking (70 °C) on CM fillets was applied to impart extending shelf-life at the market level. Using different sawdust with time-dependent smoking revealed that Oak sawdust at 25 min of optimized smoking time significantly (p < 0.05) provided the highest sensory properties (appearance, odor, color, texture and overall preferences), improved physicochemical, microbial, and nutritional properties, and subsequently, promoted shelf life of processed CM during the storage period at 10 °C for up to 34 days. Moreover, the processed CM offered high nutritional value, especially, essential and non-essential amino acids were found to be 13.14 and 15.48 g/100 g of CM fillets, and also reduced the trimethylamine-N-oxide level to an acceptable limit, indicating its quality and safety with high nutritional standards to end-point users upon consumption.

Experimental study of different sealing ratios on the self-extinction of tunnel fires

Firefighting in a long tunnel with large fires is quite difficult as the hot smoke and radiation prevent firefighters from approaching the fire seat. Sealing the portals of the tunnel to prevent the access of fresh air provides an alternative approach and it can be implemented by blocking the two tunnel portals with sand bags to prevent fresh air supply from outside after all motorists are evacuated. However, it is difficult to completely seal both portals as high pressure arises from fires. Whether partial sealing could extinguish fires or not in tunnels is an interesting topic. A series of fire tests using propane with nominal heat release rates from 2.8 kW to 11.2 kW were carried out in a 1/20 reduced-scale model tunnel measuring 10 m long, 0.45 m wide and 0.23 m high to explore the impact of different sealing ratios, varying from 0%, 65%, 75%, 85% to 100%, on the self-extinction of fires. The experimental results showed that self-extinction occurred at a sealing ratio of 75% or above except for a heat release rate of 2.8 kW, where self-extinction occur only at a 100% sealing ratio. This finding demonstrates that the partial sealing strategy at a sealing ratio of 75% or above could extinguish medium or large fires in relatively short tunnels and provides a promising method for firefighting catastrophic fires in tunnels.

An experimental study of the self-extinction mechanism of fire in tunnels

It is widely accepted that temperature decay along tunnels in fire conditions is mainly due to the heat loss to the surrounding walls and the ceiling. A previous study found fires could self-extinguish in a 1:20 reduced-scale tunnel made of steel plates and fire-proof glass and measuring 20.8 m long, 0.45 m wide and 0.23 m high (Wang et al., 2019). Self-extinction was presumed to be caused by significant heat loss at the boundaries, which led to the descent of the smoke layer and subsequently blocked the supply of fresh air. A series of experiments with fires with heat release rates of 2.8 kW, 5.6 kW, 11.2 kW and 16.8 kW were conducted in a tunnel made of fireproof board and measuring 20.8 m long, 0.45 m wide and 0.23 m high. As the heat loss at the boundaries was negligible, it was expected that self-extinction of the fires could not occur. However, self-extinction of the fires was observed, contrary to the predictions made. Furthermore, the times to reach self-extinction for the fires at different heat release rates in the two tunnels made of materials with distinctive thermal properties were basically consistent. By analyzing the velocity at different distances and scrutinizing the flow patterns using a laser sheet, it was found that the smoke velocities decreased with an increase in distance away from the fire and reduced to approximately zero at 8–9 m, irrespective of the fire sizes. While the hot smoke moves toward the portal driven by buoyancy, the same amount of makeup air flows back to the fire seat as smoke or makeup air flowing through the portals are approximately zero. The flow in the tunnel is longitudinally bi-directional and internally circulated, which persists throughout the experiment and eventually leads to the self-extinction of the fires.

Effect of ratio between incoming cool air and outgoing hot gases on behaviour of compartment fire

Many factors have an influence on the development of compartment fire notably on its heat release rate as well as on its capability to propagate and become a flashover situation. The main element which rapidly conveys fire from a compartment to another is hot smoke flowing out through openings of the compartment source of fire. The present work aims to experiment the impact of the variation of heat release rate of the source on the behavior of fire. So, five fire tests with different heat release rates were thus carried out in a reduced scale room. Temperature of burned gases inside the room, were measured during tests by sensors connected to a data acquisition system. Results revealed that temperature of burned gases as well as its content in CO, evolves differently according to two ranges of the incoming air/outgoing gases ratio. The first range of which the ratio is lower than 2, corresponds to the case where both parameters decrease rapidly. The second range of which the ratio is higher than 2, corresponds to the case where both parameters decrease moderately. The transition from the first to the second range, points out the passing from the ventilation-controlled fire to the fuel-controlled fire. A relation expressing the variation of the mass-flow rate of outgoing burned gases according to the heat release rate of the fire source has been given.

Experimental analysis of fire resistance of mortar coatings on structural masonry walls

The discussion on fire safety is necessary in Brazilian buildings. Current legislation requires construction with compartmentalized areas separated by walls with structural ceramic blocks capable of resisting fire for an amount of time pre-determined in norm NBR 14432 (ABNT, 2001). However, a lack of building standards requires experimental tests according to NBR 5628 (ABNT, 2001) to determine the necessary configuration to achieve fire resistance. For this purpose, this study analyzed the effect of fire on structural walls covered with a mortar coating. Experiments were conducted in real scale in a standardized vertical oven and the fire growth curve of ISO 834 (ISO, 1999). Three types of walls were tested, each with a different mortar coating: (a) lime; (b) 0.6 kg/m³ polypropylene fiber and 1.2 kg/m³ polypropylene fiber. The mortar coatings were 1.5 cm thick on the side facing the fire and 2.5 cm thick in the outside. The wall was composed of structural blocks measuring 14 cm x 19 cm x 29 cm. Fire experiments evaluated the structure stability, impermeability to hot gases and smoke and thermal insulation of each sample. Results showed that the structural system with 1.2 kg/m³ polypropylene fiber mortar coating obtained the best thermal insulation effect with the longest fire resistance time of 176 min.

Mineralogy and geochemistry of rare earth elements in the Moyil Valley alteration zones, Meshkinshahr (northwest Iran)

Abstract Sabalan Mountain (northwest Iran) witnessed intense volcanic activity during the Cenozoic (Plio-Pleistocene). The result of this manifests itself in the conical geometry of the Sabalan stratovolcano and ahigh hydrothermal gradient around it, which can be detected by geological phenomena such as hot springs, smoke gases and steam outlet pores. The high hydrothermal slope and upward migration of hot water in this area have caused extensive alteration zones in the host rocks. A mineralogical study of alteration zones in thewells drilled in the Moyil Valley to the northwest of Sabalan Mountain has revealed the presence of phyllic, argillic, calcitic and propylitic alterations in volcanic rocks (trachyandesite) and alteration phyllic and propylitic ones in monzonite rocks. In chondrite-normalised rare-earth-element diagrams, trachyandesite rocks exhibit an HREEs enrichment when compared to MREEs and LREEs in propylitic and calcitic alteration zones. This result can be explained by the acidic nature of hydrothermal fluids containing complex ions such as (SO-2, Cl-). The (La/Yb)cn, (La/Sm)cn and (Tb/Yb)cn ratios for argillic, phyllic, propylitic and calcitic alteration zones have revealed that they are higher in fresh rocks compared to altered rocks, suggesting the enrichment of HREEs in comparison to LREEs and MREEs. The anomalies of Eu do not change remarkably in the argillic and propylitic alteration zones of trachyandesite rocks; apparently, alteration hadno effect on them. Such behaviour reflects the presence of gold cations in Eu+3 formed at temperatures below 250°C. Eu anomalies increased in propylitic alteration zones in monzonite rocks and calciticand phyllic alteration zones in trachyandesiterocks.

Measurement of smoke generation rate using a full-scale hot smoke test for building smoke exhaust systems

In some countries, test standards have been adopted which measure the effectiveness of smoke exhaust systems in clearing out heat and smoke produced separately. However, because these standards provide no quantitative provisions for dealing with the amount of visual smoke, there is an unclear correlation between the amount of smoke generated and the fire load. This paper applied the homogeneity concept of using a smoke collection box to examine the smoke generation rate of a smoke generator using CO2 as the driving gas. To avoid using the previous visual method of judging the rates, this research used measurement equipment to conduct a scientific analysis. Thus, the results were more objective. The equipment used included a Closed-Circuit Television (CCTV) Camera, a thermocouple, a traditional P-type smoke detector, a digital R-type smoke detector, and light attenuation measurement equipment. Under release pressures of 40, 60 and 80 psi, a 15% smoke density required smoke generation at 6.50, 8.42 and 10.46 m3/s, respectively. Achieving a homogeneous distribution of smoke within the space was accomplished. The data obtained in the test could be used not only to judge the efficiency of a smoke exhaust system but also provide adjustment information for a smoke exhaust system.

Effect of heat release rate and exhaust vent settings on the occurrence of plug-holing during tunnel fires with two-point extraction ventilation

This paper investigated the plug-holing phenomenon in the tunnel fire with two-point extraction ventilation based on a reduced-scale tunnel model. The effect of the heat release rate (HRR) and extraction vent settings, i.e. the area and aspect ratio (a ratio of the width to the length), on the occurrence of plug-holing was addressed experimentally and theoretically. Experimental results show that the exhaust volumetric flow rate of the occurrence of plug-holing increases with the growth of the HRR and aspect ratio. Besides, with the extraction vent area rising, the exhaust volumetric flow rate of plug-holing improves. However, when the extraction vent area is larger than a certain value, the hot smoke cannot fill the entire extraction vent and may adhere to the upstream of the extraction vent, which is different from the plug-holing. Finally, an empirical equation was developed to predict the occurrence of plug-holing with various HRRs and extraction vent settings based on a proposed modified Froude number in this paper. Research outcomes can provide constructive references for the current design of the point extraction ventilation in tunnel fires.

Impact of air intake position on fire dynamics in mechanically ventilated compartment

The effects of air intake position on the burning behaviour of liquid pool inside a mechanically ventilated compartment are analyzed by using both an experiment and a physics-based model. A series of compartment fire experiments has been undertaken from a reduced scale enclosure with a length/height and width of 2 m. An external ventilation system consists of an air admission duct placed in low or high position inside the compartment, providing an Air Change Per Hour (ACPH) in a range from 1 to 4. Lowering the inlet duct enhances fuel-air mixing in the compartment. The experimental and numerical studies highlight a faster fire growth for a low air intake with a rise of ACPH, implying more dangerous fire with regarding the more important peak in heat release rate and heat feedback to liquid fuel surface. For air intake in high position, the direction of air jet inside enclosure is found to be orthogonal to the direction of the buoyancy-induced flow. This results in an air entrainment restriction towards the fire base and a decrease of the heat feedback to liquid fuel surface due to cooling effect on the hot smoke layer near the ceiling. Thus a high inlet contributes to a reduction by a factor of 40% in HRR, and the fire growth power is practically independent to ACPH. Moreover, for a high inlet, fire exhaust occurs more easily because both the heat feedback and air entrainment are weaker than these for a low inlet. As a consequence, changing air intake position from low to high leads to a change in fire regime from an under-ventilated fire to an over-ventilated one.

Stairwell smoke transport in a full-scale high-rise building: Influence of opening location

In this study, a series of experiments were conducted with varying number of pool fires and opening location (floor with ventilation openings) in a 21-story full-scale office building to study the transport phenomena and stratification of hot smoke in the stairwell. The experiments show that the flame of the pool fire inclines away from the side lobby door as pushed by the side air entrainment. The strength of stack effect in the stairwell initially increases, then decreases with the opening height increases. The rise in temperature in the stairwell can be divided into a lower and an upper region, depending on the location and attenuation effect of the upper opening. In the lower region, both the stack effect and turbulent mixing play important roles in the movement of hot smoke, whereas in contrast, in the upper region, turbulent mixing dominates. The equivalent heat release rate for hot smoke in the upper region is determined through theoretical analysis, and an integrated correlation is proposed for predicting the rise time of the smoke plume in the stairwell. These unique full-scale experiments provide crucial experimental data and empirical correlations that help the design of safer smoke ventilation systems for stairwells in a high-rise building.

The Levels of Polycyclic Aromatic Hydrocarbons in Traditionally Smoked Cheeses in Poland

Smoked cheeses are especially appreciated by consumers because of the unique taste and smell. The smoke used in this process is composed of a few hundred components, both favorable influencing the smoked product quality and neutral for consumers’ health, and also the ones which are questionable because of health aspects, for example, polycyclic aromatic hydrocarbons (PAHs). Even though such substances decide about the taste and smell of smoked products, they are perceived as potentially genotoxic and cancerogenic for humans. The aim of the experiment was to assess the PAHs levels in traditionally smoked cheeses in Poland. The PAHs in cheeses samples were determined by isotope dilution method with the use of HRGC-HRMS. The cheeses contained the trace amounts of benzo[a]pyrene. The except were small sheep cheeses and the Ritta goat whey cheese smoked in hot smoke in which the level of 17.0 µg/kg of benzo[a]pyrene was observed. The low levels of benzo[a]pyrene and of sum of benzo[a]pyrene, benzo[a]antracene, benzo[b]fluorantene and chrysene in the analyzed cheeses were the result of mild smoking in warm smoke. Although today, there are no regulations about smoked cheese and the maximum of PAHs concentration, the control of PAHs in the cheeses is essential due to the mutagenic and carcinogenic potential of these compounds.

Experimental and numerical study of smoke behavior in high-rise stairwells with open and closed windows

This study numerically and experimentally investigates the transport phenomena in buoyancy-driven smoke inside stairwells in a high-rise building. Hot smoke is supplied at the bottom of a small-scale, 2-m high stairwell prototype, and the smoke velocity and temperature are measured and compared with the corresponding numerical results. For all-windows-closed cases, the Fire Dynamics Simulator (FDS) model is used to predict the smoke velocity and temperature fields, which are found to be in good agreement with the experimental data. Obstruction caused by the stairs is observed to slow the smoke flow, which results in staggering and repeated vortical flows in all stairwells, confirmed by flow visualization. The flow path lines and vortex formation of the smoke inside the stairwells are visualized using the laser-induced fluorescence (LIF) method; these vortical structures also corresponded to the results of FDS simulation. Furthermore, the effect of heating power (Q) is investigated in the range of 60–180 W for experiments and 1–4 kW for simulations. Both temperature and velocity increase with Q. Having one open window at various building heights is shown to have small effect on the overall smoke temperature, although having many open windows causes a temperature drop owing to the inflow of fresh, cool air. Having one open window at various building heights slightly slows the smoke velocity, although the velocity is significantly decreased when many windows are open. Therefore, the intake of fresh air slows the overall smoke dynamics. Moreover, the effect of Q in the range of 2–20 MW over building heights of 60, 120, and 240 m is numerically simulated. The rate at which the smoke reaches high elevations is determined for all-windows-closed and all-windows-open cases based on our parametric studies. The smoke rise time (t) is shown to be proportional to ~ Q-1/3 for all building heights, which is the same time scale as the one predicted by the plume theory. However, because of the complex internal geometry of confined buildings including stairwells and corridors, the magnitude of the smoke rise time for the building is much larger than that predicted by the plume theory. Therefore, the current experimental and numerical findings may be useful as design guidelines for building safety engineers.