Natural Smoke Research Articles

Study on the Natural Smoke Exhaust Performance of Board-Coupled Vertical Shaft in High-Altitude Tunnel Fires

Vertical shaft natural ventilation is a common smoke exhaust method in highway tunnel fires. This study investigated the vertical shaft natural smoke exhaust work in highway tunnel fires with the effect of multiple factors through numerical simulation. Using the analysis of the flow field of smoke in nearby areas of the vertical shaft and the quantitative calculation of the gas exhausted through the vertical shaft, considering the impact of shaft division and board height, an optimal vertical shaft arrangement was proposed, and the working conditions of this arrangement in low-pressure environments were discussed. The results show that dividing a single large vertical shaft into multiple small vertical shafts and appropriately adjusting the board height can reduce the incidence of vertical shaft plug holes and significantly enhance the vertical shaft smoke exhaust performance. Meanwhile, the board-coupled shaft (BCS) has excellent working ability in low-pressure environments, and when pressure drops, smoke exhaust efficiency will improve. This research offers a foundation and reference value for improving the vertical shaft smoke exhaust system in highway tunnels.

Climate-adaptive fire smoke ventilation strategies for atrium-type metro stations: A NSGA-II multi-objective optimisation study

This study explores the impact of climate variability on the operation of sustainable ventilation systems in urban infrastructure, with a focus on smoke movement in metro stations under varied external climatic conditions. Smoke characteristics and ventilation strategies in an atrium-type metro station are investigated using numerical simulations. The simulations reveal the influence of external climate on smoke movement through the atrium and roof windows, with particular attention to outdoor temperature and wind velocity. The study designs different ventilation strategies for smoke control that incorporate meteorological data, evaluating smoke visibility, CO distribution, and smoke extraction efficiency. The findings indicate that under severe external climates of low temperatures and high wind velocities, smoke extraction from roof window outlets is challenging. The adverse effects of external climate decrease the natural smoke extraction efficiency, increase the CO concentration, and reduce the safe visibility area. However, improved ventilation measures, such as the platform make-up air system and roof mechanical extraction system, can significantly enhance smoke control performance and facilitate safe evacuation. The study also employs the NSGA-II multi-objective optimisation method to obtain optimal ventilation strategies for different climates, balancing three optimisation objectives of operating energy consumption, safe visibility area, and smoke extraction efficiency. The outcomes show that the recommended values of Vp are 20%–30 % (0 °C ≤ To≤40 °C) and 40 % (−40 °C ≤ To<0 °C), vr are 0.3 (10 °C ≤ To≤40 °C) and 0.4 (−40 °C ≤ To < −10 °C), and Vc are all lower than 4 %. As wind velocity increases, the recommended values need to be enhanced. This research contributes to sustainable urban development by offering a framework for managing public safety and energy efficiency in the context of climate variability.

AMP, ADP, and ATP Concentrations Differentially Affected by Meat Processing, Manufacturing, and Nonmeat Ingredients

Given its presence in a wide spectrum of soils relevant to food process hygiene, the biological metabolite adenosine triphosphate (ATP) is used as a target for surface hygiene assessments in food processing facilities. Yet, ample evidence demonstrates that ATP is depleted into adenosine di- (ADP) and monophosphate (AMP) homologs resulting in a loss of sensitivity for ATP-based hygiene assays. Yet, there are few studies that denote the degree of these shifts under routine processing conditions such as those encountered during various meat processing steps that may likely alter redox potential and adenosine profiles (e.g., tissue/cellular disruption, application of reducing additives, fermentation, or thermal treatment steps). In this study, meat samples were collected from homogenized beef tissue treated with nonmeat ingredients (sodium chloride, sodium nitrite, sodium erythorbate, natural smoke condensate, and sodium acid pyrophosphate) during manufacture at predetermined steps, and from retail meat products purchased from local markets. Concentrations of ATP, ADP, AMP, and AXP (sum concentration of all homologs) in a lab setting and in situ meat processing venues were determined and compared. Greater differences in AXP were seen during manufacture, where ADP generally comprised ∼90% as a mole fraction of AXP across all treatments, with the exception of the final cook step where AMP predominated. ATP concentrations averaged 2 log values lower than ADP and AMP. Adenosine profiles in retail samples followed similar trends with minimal ATP concentrations with ADP predominant in uncooked samples and AMP predominant in cooked samples. Resultingly, meat processing steps during product manufacture will alter AXP-reliant test sensitivities which should be considered when such technologies are utilized for hygiene verification in meat processing.

Investigation on the natural smoke exhaust performance by vertical shaft in tunnel fires under different ambient pressures

In high-altitude tunnels, due to the ambient pressure and density of air being different from those under normal pressure, the convection and heat radiation in tunnels are also different when fires occur. As a result, the smoke exhaust capacity varies under different pressures. This work aimed to numerically explore the impact of ambient pressure on the smoke exhaust efficiency at high-altitude shallow tunnels with natural ventilation by shaft. The numerical results demonstrated that the smoke exhaust capacity is enhanced with increasing ambient pressure. This is because of the increase in the air entrainment coefficient and air density, and it causes plug-holing more easily to occur under higher ambient pressures. Once the plug-holing has taken place, the fresh air can be directly exhausted through the shaft, which results in a poor smoke exhaust capacity. By accounting for the factors of the smoke layer thickness, ambient pressure, the exhausted smoke temperature and heat release rate, the Richardson number was introduced as the criterion for determining whether plug-holing occurs. As ambient pressure was increased, the critical Richardson number for plug-holing was observed to decrease, a finding supported by existing research.

Smoke exhaust characteristics under stack effect of natural ventilation by shaft in high-altitude tunnel

The number of high-altitude tunnels is increasing year by year and natural ventilation of shafts is widely used as a critical component of the ventilation system. For the design of ventilation systems, it is particularly crucial to consider the smoke exhaust performance of shafts in low-pressure environment. Therefore, this study simulates tunnel fires with natural ventilation by shaft in high-altitude areas, aiming to analyze the impact of atmospheric pressure on smoke exhaust performance and smoke exhaust capacity by natural ventilated shafts at 50 to 100 kPa atmospheric pressure. It appears from the results that the increasing of ambient pressure can enhance the ability of air entrainment and natural smoke exhaust, and thus plug-holing is more likely. In which condition, fresh air can be expelled straight from the shaft, reducing smoke exhaust efficiency. As ambient pressure increases, the critical shaft height for plug-holing decreases. By analyzing the smoke exhausting process by shaft and smoke flow, smoke exhaust capacity can be evaluated by obtaining the mass flow rate of exhausted smoke and fresh air from the shaft under various atmospheric pressures and fire source power and. It could be said that increasing ambient pressure and shaft height can improve the smoke expulsion performance before plug-holing. However, once plug-holing happens, the increase of shaft height can no longer expel more smoke but much more air is exhausted by shaft. It is hoped that this work will serve as a guideline for ventilation systems design in high-altitude tunnels.

Study on Smoke Spreading Characteristics of Highway Tunnel Fire

In the event of a fire in a road tunnel, the effect of natural smoke exhaust alone is far inferior to that of mechanical smoke exhaust. Study of the characteristics of the flux of smoke gases inside the tunnel with the use of mechanical exhausts in case of sudden fire in road tunnels by means of specific model simulation methods, specific analysis by setting fixed exhaust spacing and different emission volumes, and the addition of fine water mist is studied. The results show that: when the exhaust vent spacing is 30m, the smoke exhaust volume in 30m³/s, 40m³/s, 50m³/s mechanical smoke exhaust device under the action of temperature, CO concentration and visibility will not affect the safe evacuation of the personnel, but taking into account the control of smoke propagation and economic reasonableness, the smoke exhaust volume of 40m³/s is better than the smoke exhaust volume of 30m³/s and 50m³/s. Under the coupling effect of mechanical smoke exhaust system and fine water mist, the spread of smoke in the tunnel can be controlled within a certain range and the internal temperature of the tunnel can be reduced. It can provide a certain basis for the design of the exhaust vent and the setting of water mist in the future.

Comparative Analysis of Korean and Japanese Standards for Natural Smoke Ventilation in Logistic Warehouses

This study investigated the design methodologies outlined in Korean and Japanese legislation, along with Japanese design guidelines, pertaining to natural smoke ventilation systems in logistics warehouses. Subsequently, we determined the effective area of the smoke exhaust system based on the combustible materials and building characteristics. Our findings indicated that the calculated effective area per the statutory standards of both nations was 10 m&lt;sup&gt;2&lt;/sup&gt; and 20 m&lt;sup&gt;2&lt;/sup&gt;, respectively. According to Japanese guidelines, the space accommodating the CUP ranged from 24.71 m&lt;sup&gt;2&lt;/sup&gt; to 13.76 m&lt;sup&gt;2&lt;/sup&gt; for floor heights between 7 to 16 m, while the space accommodating CEP ranged from 41.83 m&lt;sup&gt;2&lt;/sup&gt; to 22.54 m&lt;sup&gt;2&lt;/sup&gt;. Analyzing the quantity of smoke emitted through the calculated effective area, we observed that, when applying domestic legal standards, the smoke exhaust rate consistently remained lower than the plume flow rate. Conversely, under the Japanese standard, the smoke emission efficiency of the CUP loading warehouse surpassed that of smoke emission from 9 m to 16 m, while it was lower from 7 m to 8 m. Notably, the smoke exhaust rate consistently exceeded the generated smoke quantity in all instances within the effective area governed by the guidelines.

Investigating the influence of outdoor temperature variations on fire-induced smoke behavior in an atrium-type underground metro station using hybrid ventilation systems

Underground metro systems are expanding rapidly worldwide, necessitating research on energy-efficient ventilation systems, fire safety, and smoke control. This study investigates the optimisation of hybrid mechanical-natural ventilation for smoke control in complex metro stations. Full-scale winter/summer experiments and numerical simulations examined a double-deck atrium-type station. Results demonstrate the atrium fires are more significantly impacted by outdoor temperature variations versus concourse/platform fires, with a 70 K versus 30 K temperature rise above the fire respectively. The heat of the gathered high-temperature smoke inside the atrium can reach up to 900 K under a 5 MW train fire energy release. The dimensionless Archimedes number (Ar) defines the ratio of thermal buoyancy to gravitational forces. Cold exterior winter air (Ar<1) entering via the atrium ceiling openings restricted vertical smoke diffusion, enabling enhanced lateral propagation. With rising outdoor temperatures from −20 °C to 10 °C (Ar<1), the natural smoke extraction efficiency increased from 0 to 18 %, coupled with vertical airflow velocities accelerating from −3.5 m/s to 1.5 m/s. When outdoor temperatures were between 10 °C and 40 °C (Ar>1), airflow velocity only changed slightly. Empirical models predict internal temperature profiles as a function of external meteorology. The findings provide crucial engineering insights into integrating weather data and adaptable ventilation protocols for scenario-based smoke prevention/mitigation. Further work should examine seasonal variations beyond the tested -20‒40 °C range. Overall, considering outdoor climate effects allows 30 % optimisation of hybrid ventilation systems for fire safety in underground metro stations. This study promotes technological advances in energy-efficient transport infrastructure resilience.

Discussion on the Analysis of Fire Hazard in the Central Hall of a Historical Building

This study focuses on the inadequate compliance of natural smoke exhaust windows in the central hall of a historical building in Shanghai. Taking into consideration the preservation of the authenticity of the historical structure, five fire scenarios were established to evaluate the fire hazard in the central hall based on different fire heat release rates, fire growth coefficients, number of open windows and window response times. Considering the actual conditions of the historical building and its function as a medical facility, the study also analyzed the rationality of setting fire scenario parameters for evacuation time and fire safety assessment. The research findings indicate that the upper smoke temperature is significantly influenced by the values of heat release rate and the number of open windows. Increasing the number of open windows by 60% can extend the time for the upper smoke temperature to reach a dangerous state by approximately 10%.

Indoor Fire Simulation in Low-Rise Teaching Buildings Based on BIM–FDS

School buildings gather a large number of underage students, and the disastrous consequences of fire in such buildings are very serious, which is one of the key concerns of society in fire prevention and control. This study takes a “[” type kindergarten teaching building as the background and constructs a BIM–FDS building fire simulation model to reveal the fire smoke dispersion law under the coupling of the typical building structure and fire protection systems. The results show that the stairwells on both sides of the “[” type building are the main channels for the diffusion of fire smoke, and the asymmetry of the stairwell structure will cause apparent differences in the diffusion of smoke. Using the natural smoke exhaust in the stairwells of low-rise buildings does not aggravate the spread of smoke in the building and is conducive to smoke emissions. The high-pressure water mist system is superior to the water spray system in fire extinguishing and controlling room temperature. While it reduces smoke exhaust performance, it does not adversely affect personnel evacuation. This study systematically reveals the law of diffusion of fire smoke from “[”-type teaching buildings, which can support the design of similar building structures, ventilation, fire protection, and the formulation of fire escape plans.

Numerical Simulation on Smoke Temperature Distribution in a Large Indoor Pedestrian Street Fire

In order to study the characteristics of fire smoke spread and temperature distribution of a large indoor pedestrian street under different heat release rates and smoke exhaust modes, this paper focuses on the analysis of fire smoke spread, visibility, smoke temperature distribution and variation curves in an atrium. This paper uses a numerical simulation method to conduct research. PyroSim fire simulation software is used to calculate this project, which is based on a full-scale experimental design scheme. The numerical simulation results show that under the conditions of higher heat release rate, the smoke spread rate is greater than that under the conditions of lower heat release rate. Furthermore, the average temperature of smoke in the atrium is also greater, up to about 400 °C. The conditions of a higher heat release rate also show the characteristics of faster generation, faster spread and a larger volume of smoke. When the smoke exhaust system is turned on, the thickness of the smoke layer and the smoke temperature decrease. There then comes a situation where the stabile section of the fire ends in advance. The simulation results of vertical temperature distribution in an atrium can fit the modified McCaffrey plume model in any case. Under all cases, the smoke temperature reaches the maximum directly above the fire source. The horizontal dimensionless smoke temperature rises under the atrium roof, and decreases exponentially with the dimensionless distance from the fire source. The greater the heat release rate of fire source is, the smaller the attenuation coefficient is, with a more than 50% change. When the smoke exhaust system is turned on, the smoke flow accelerates and the smoke is cooled rapidly. Thus, the attenuation coefficient increases. Additionally, the effect of mechanical smoke exhaust is better than natural smoke exhaust, because mechanical smoke exhaust makes air flow and heat exchange more intense. The variation amplitudes of the attenuation coefficient under natural smoke exhaust and mechanical smoke exhaust are 13% and 22%, respectively.

Numerical assessment on aerodynamic free area of natural smoke and heat exhaust ventilator without and with side wind

As a convenient means for modeling the dynamics of fluids, computational fluid dynamics has not yet been fully applied in the refined quantitative analysis of the effectiveness of individual smoke ventilator. Previous related numerical simulation studies were short of the overall consideration of various verification scenarios involving all aspects of performance of testing device and accuracy of testing results without and with side wind. In this paper, a comprehensive numerical assessment process containing seven typical simulation scenarios is established for determining the aerodynamic free area of a roof mounted ventilator without and with side wind. Compared with related on-site testing platform, the geometric construction of testing apparatus is reasonably optimized to obtain more uniform flow field inside the settling chamber and more appropriate coverage of side-wind field acting on the ventilator; some measurement positions of air speed, which are unspecified in the testing standard, are designed properly in the simulation. Six types of regression equations on the relationship between discharge coefficient and pressure difference are established and compared for exploring the best goodness of fit of curve fitting. Good agreement of simulation results with reference data demonstrates the feasibility and validity of the numerical assessment process developed in this study.

A New, Green, Recyclable Fireproof Insulation Board for Use in Integrated Composite Structure Fire Protection Systems

A fireproof insulation board can be recycled, and the raw materials used in its production are very environmentally friendly, non-toxic and non-hazardous, and bring no harm to the human body and the surrounding environment. One practical application of fireproof insulation board is in an integrated composite structural fire protection system, which is a multidimensional comprehensive structural fire protection system proposed for the combined construction of buildings with different functions, such as horizontal and vertical, to ensure overall safety in the event of a building fire. The specific new technology of this new system includes an integrated structural fire protection system composed of a 3.00 h fire insulation board, which comes from the collection of textile scraps consisting of metals and buttons removed from clothes. To prove the effectiveness of this fireproof insulation board, its parameters were collected and put into FDS (FirG Dynamics Simulator, a CFD model of fluid flow during combustion developed by the National Institute of Standards and Technology), the fire safety goals considering the safety of building and personnel were established, and fire scene design based on the statistics of fire data and building codes was generated to test the safety of evacuation. To ensure the reliability of simulation results, an on-site physical fire test was conducted with the recycled insulation board. The result shows that the function of recycled board optimizes the phased evacuation design plan of personnel and solves the design difficulties of expanding fire zones and long evacuation distances when used in warehouses. Through the innovative design of the roof opening rate set at 30% and a hole spacing of 60 m, this underground fireproof insulation board is guaranteed to possess natural smoke exhaust conditions and can be used to improve public safety areas.

Effect and Analysis of Different Types of Smoke Exhaust Window on Natural Smoke Exhaust Effect

Effect and Analysis of Different Types of Smoke Exhaust Window on Natural Smoke Exhaust Effect

Numerical Simulation on the Effect of Fire Shutter Descending Height on Smoke Extraction Efficiency in a Large Atrium

In this study, a series of numerical simulations were carried out to investigate the effect of fire shutter descending height on the smoke extraction efficiency in a large space atrium. Based on the full-scale fire experiments, this paper carried out more numerical simulations to explore factors affecting the smoke extraction efficiency in the atrium. The smoke flow characteristics, temperature distribution law and smoke extraction efficiency of natural and mechanical smoke exhaust systems were discussed under different heat release rates and fire shutter descending heights. The results show that the smoke spread rate and the average temperature of the smoke are higher with a greater heat release rate. After the mechanical smoke exhaust system is activated, the smoke layer thickness and smoke temperature decrease, and the stable period of heat release rate is shorter. In the condition of natural smoke exhaust, the smoke extraction efficiency increases exponentially with the increase of heat release rate and the descending height of the fire shutter, and the maximum smoke extraction efficiency is 48.8%. In the condition of mechanical smoke exhaust, the smoke extraction efficiency increases with the increase of mechanical exhaust velocity. When the velocity increases to the critical value (8 m/s), the smoke extraction efficiency is essentially stable. The smoke extraction efficiency is increased first with the increase of fire shutter descending height and then has a downward trend when the descending height drops to half, and the maximum smoke extraction efficiency is 70.3% in the condition of mechanical smoke exhaust. Empirical correlations between the smoke extraction efficiency and the dimensionless fire shutter descending height, the dimensionless heat release rate and the dimensionless smoke exhaust velocity have been established. The results of this study can provide a reference for the design of smoke prevention and exhaust systems in the atrium.

Fire Safety Evaluation of Natural Smoke Ventilators Opening to outside due to Changing Outside Wind Speed

The reduction of the smoke exhaust performance of the natural smoke ventilator due to the influence of the external wind speed causes the problem of not being able to appropriately exhaust the heat and smoke generated by the fire compartment into the outflow air, which has a huge impact on the evacuation of the occupants, and at the same time can be a major problems to remaining life safety and fire suppression of the fire brigade. In this study, the type of projected window natural smoke ventilators opening to exterior which was selected from the preliminary smoke performance evaluation study and then the fire simulation was performed to quantitatively evaluate the smoke exhaust performance of the n atural smoke v entilator by the s iz e of the outside w ind speed. A s a result of the analysis, a s the wind speed increased, the smoke exhaust performance of the natural smoke ventilator was further reduced, and the amount of flue smoke due to the inlet flow was reduced, and it was predicted to negatively affect the main evacuation factors such as smoke layer height and fire room temperature.

Effect of Opening Size on the Development of Ventilation-limited Fire

There are many factors, that affect the development of indoor fire, such as the size of the fire source, the opening or space of the room, and the nature of the combustible materials. Among them, the space of the room, has a significant impact on the development of a ventilation-limited fire. In this paper, the Fire Dynamics Simulator (FDS) software is used to analyze, the risk of fire initiation in the restricted ventilated compartment, when the size of vertical ventilation space is different. Through, a combination of experimental design, numerical simulation, and theoretical analysis, the changes in the level of carbon monoxide, visibility, temperature, Heat Release Rate (HRR) and, the smoke exhaust efficiency of natural smoke at different opening sizes are observed. It is observed that, when the ratio of inlet and outlet area reaches 2:1, the natural smoke exhaust effect is the best, however, the increasing in the opening size has little significance on the smoke exhaust effect. The research on the influence of smoke outlet size, will helps in the development of the law regarding fire prevention, smoke exhaust design, and fire rescue work of a building.

The Impact of Outdoor Temperatures on the Efficacy of Natural Ventilation and Smoke Exhaust Systems

Natural smoke control systems in staircases are one of the available systems used for the protection of escape routes from smoke and are one of the most utilised for medium to high rise buildings. However, their effectiveness (as well as other ventilation systems) is strongly dependent on the weather conditions, especially the outdoor temperature. This paper describes the results of real-scale experiments of the airflow in a staircase’s natural smoke exhaust system. The experimental staircase was localised in a medium-high building, “LabFactor” at the Lodz University of Technology in Poland. The experiments were performed over a period of six months, from February to July 2019, and included measurements of external and internal air temperature as well as the airflow through the staircase. The results obtained enabled an evaluation of the effectiveness of the ventilation and natural smoke exhaust system in the staircase, in relation to external temperatures. It was found that natural smoke exhaust systems could operate below an acceptable level of effectiveness for nearly 25% of the year. The experimental results were confirmed with CFD simulations.

The Impact of COVID-19 Lockdowns on Satellite-Observed Aerosol Optical Thickness over the Surrounding Coastal Oceanic Areas of Megacities in the Coastal Zone

Nearly 40 years of aerosol optical thickness (AOT) climate data record (CDR) derived from NOAA operational satellite Advanced Very High Resolution Radiometer (AVHRR) observation over the global oceans is used to study the AOT changes due to the COVID-19 lockdown over the surrounding coastal oceanic areas of 18 megacities in the coast zone (MCCZ). The AOT difference between the annual mean AOT values of 2020 with COVID-19 lockdown and 2019 without the lockdown along with the 2020 AOT annual anomaly are used to effectively identify the AOT changes that are a result of the lockdown. We found that for most of the 18 MCCZ, the COVID-19 lockdowns implemented to contain the spread of the coronavirus resulted in a decrease between 1% and 30% in AOT due to reduced anthropogenic emissions associated with the lockdowns. However, the AOT long-term trend and other aerosol interannual variations due to favorable or unfavorable meteorological conditions may mask AOT changes due to the lockdown effect in some MCCZ. Different seasonal variations of aerosol amount in 2020 relative to 2019 due to other natural aerosol emission sources not influenced by the lockdown, such as dust storms and natural biomass burning and smoke, may also conceal a limited reduction in the annual mean AOT due to the lockdown in MCCZ with relatively loose lockdown. This study indicates that the use of long-term satellite observation is helpful for studying and monitoring the aerosol changes due to the emission reduction associated with the COVID-19 lockdown in the surrounding coastal oceanic areas of MCCZ, which will benefit the future development of the mitigation strategy for air pollution and emissions in megacities.

Influence of opening ratios and directions of windows on natural smoke exhaust effect in atrium buildings

Influence of opening ratios and directions of windows on natural smoke exhaust effect in atrium buildings