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During anatomy dissection, the release of formaldehyde (FA) from cadavers and embalming fluids can negatively affect the well-being of students and staff. The exposure of students, staff, and technicians to FA in the dissection hall is a concern. To address this issue, a study measured the FA and air quality (CO2 and Total Volatile Organic Compounds- TVOC) with different ventilation setups: natural, fan-based, and air-conditioned. The FA levels and the indoor air quality at the breathing zone were estimated using an air conditioning (AC), fan-based, and naturally ventilated setup. The FA, CO2, and TVOC levels were calculated at the cadavers' head and toe ends, in the pathway, and between the dissection tables. The FA, CO2, and TVOC levels were higher near the cadaver and lower in the pathway and between the tables, regardless of the type of ventilation used. Fan-based ventilation had the lowest mean FA, CO2, and TVOC levels compared to AC and natural ventilation. However, there was no significant difference in these levels between the ventilation types, except for the toe-ends of the cadavers (P <.05), where the toe-end farther from the AC vents had higher levels. The study suggests that areas away from the source of ventilation in the anatomy dissection hall are at risk of having lower air quality. Therefore, in addition to selecting an appropriate ventilation system, placing the donor bodies near the source of ventilation would help optimize FA levels and improve indoor air quality for better working conditions suitable for students and staff. Plain language summary: In anatomy labs, the chemicals used to preserve bodies can be harmful to the people working there. A study looked at how different ways of getting fresh air into the lab could help. We found that using fans to bring in fresh air resulted in the lowest levels of harmful chemicals. The study suggests that placing the bodies near the source of fresh air can help make the air safer for students and lab staff. [ABSTRACT FROM AUTHOR]

As the depth of mine excavation increases, ventilation shifts from an easy to a challenging phase. To address potential issues of high temperature and low airflow in the underground working face of Yanqianshan Iron Mine, 2 optimization plans were proposed with the -269 m level as the research subject. A 3D visualization simulation model of the underground ventilation system was created, and mine ventilation system network analysis software was used for 3D simulation and network calculations to simulate and analyze the optimization plans. Numerical simulation results of the optimized ventilation system showed that Plan 1 increased the average airflow in the northern area of the -269 m roadway by 1. 13 m³/s and decreased the temperature by an average of 0. 14 ℃ . Plan 2 increased the overall airflow in the -269 m roadway by an average of 5. 51 m³/s, with a temperature reduction of 0. 34 ℃ in most roadways near the mining area. A comparison indicates that Plan 2 provided a greater increase in airflow and a wider impact range for temperature reduction. Both plans improved the ventilation system, offering valuable reference for optimizing underground ventilation systems in most domestic underground mines. [ABSTRACT FROM AUTHOR]

Objective. The identification of increased noise levels from ventilation systems during the operation of buildings necessitates complex and costly procedures to detect and eliminate noise sources, conduct dismantling work, install additional silencers, or replace ventilation equipment. Therefore, accurate acoustic calculations are one of the most critical tasks in the design of various facilities. Method. This article presents an analysis of domestic and international methods for determining the noise generated by throttling devices. The accuracy of the calculation results was evaluated by comparing them with data from field tests. Result. A sharp increase in sound power level within the throttling device was observed when the blade angle exceeded 60 degrees, significantly impacting the acoustic environment of the premises and leading to an exceedance of regulated noise levels. Conclusion. The conducted comparative analysis of existing calculation methods revealed that the domestic calculation method provides the required margin for the sound power level of the throttling device across all octave bands. A notable drawback of international calculation methods is the lack of consideration for the acoustic impact of duct fittings and the connection of the duct to the throttle, which underscores the need for further validation of these methods for complex systems.

The purpose of the study was the impact of different types of ventilation systems in boar`s pen on the microclimate and their physiological parameters. The control group of boars was kept in a house with a transverse ventilation system, and the animals of the experimental group were kept in a geothermal air supply. It was found that, regardless of the season, transverse ventilation provides a significantly higher air velocity and relative humidity: in Winter - 0.15 m s–1 and 5.4%; in Spring - 0.35 m s–1 and 5.3%; in Summer - 0.41 m s–1 and 0.7%; in Autumn - 0.28 m s–1 and 8.1%. Maintaining a stable temperature by the normative values in the boar housing was due to geothermal ventilation, regardless of the season, especially the "basement effect" was observed in the summer months, where the air temperature was cooled to 4.5°C (P < 0.001), compared to the transverse ventilation system. Compared with the boars in the experimental group, under the influence of the temperature increase in Summer, the boars in the control group increased significantly the respiratory rate to 50.9 ppm (P < 0.001) and heartbeat rate of 45.7 ppm (P < 0.001). An increase in rectal temperature in boars at elevated ambient temperature under both air ventilation systems was not found. The obtained results make it possible to introduce the use of cost-effective geothermal air supply technology in pig farms to harmonize the physiological parameters of boars to meet their biological needs, even in closed housing to improve their welfare. [ABSTRACT FROM AUTHOR]

Copyright of Railway Construction Technology is the property of Railway Construction Technology Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

To control the diffusion of high concentrations of coal dust during tunnel boring and minimize the threat to the life and health of coal miners, theoretical analysis, numerical simulations, and field measurements were combined in this study. First, computational fluid dynamic simulation software was used to simulate the generation of dust particles and their transport pattern in the tunnel. Subsequently, an innovative orthogonal test was performed to study the effect of four ventilation parameters [the pressure airflow rate (Q), distance between the air duct center and heading face (LA), distance between the air duct center and tunnel floor (LB), and distance between the air duct center and nearest coal wall (LC)] on dust diffusion. According to the orthogonal test results, the optimal ventilation parameters for effective dust control are as follows: Q = 1400 m3/min, LA = 7 m, LB = 2.8 m, and LC = 1 m. The optimized set of ventilation parameters was applied to the Wangpo 3206 working face. The results show that dust diffusion in the tunnel was effectively controlled and that the air quality was sufficiently improved. [ABSTRACT FROM AUTHOR]

Copyright of Chinese Medical Equipment Journal is the property of Chinese Medical Equipment Journal Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Abstract Nitrogen is widely used in various laboratories as a suppressive gas and a protective gas. Once nitrogen leaks and accumulates in a such confined space, it will bring serious threats to the experimental staff. Especially in underground tunnels or underground laboratories where there is no natural wind, the threat is more intense. In this work, the ventilation design factors and potential leakage factors are identified by taking the leakage and diffusion of a large liquid nitrogen tank in China Jinping Underground Laboratory (CJPL) as an example. Based on computational fluid dynamics (CFD) research, the effects of fresh air inlet position, fresh air velocity, exhaust outlet position, leakage hole position, leakage hole size, and leaked nitrogen mass flow rate on nitrogen diffusion behavior in specific environments are discussed in detail from the perspectives of nitrogen concentration field and nitrogen diffusion characteristics. The influencing factors are parameterized, and the Latin hypercube sampling (LHS) is used to uniformly sample within the specified range of each factor to obtain samples that can represent the whole sample space. The nitrogen concentration is measured by numerical value, and the nitrogen diffusion characteristics are measured by category. The GA-BP-ANN numerical regression and classification regression models for nitrogen concentration prediction and nitrogen diffusion characteristics prediction are established. By using various rating indicators to evaluate the performance of the trained model, it is found that models have high accuracy and recognition rate, indicating that it is effective in predicting and determining the concentration value and diffusion characteristics of nitrogen according to ventilation factors and potential leakage factors. The research results can provide a theoretical reference for the parametric design of the ventilation system.

Nitrogen is widely used in various laboratories as a suppressive gas and a protective gas. Once nitrogen leaks and accumulates in a such confined space, it will bring serious threats to the experimental staff. Especially in underground tunnels or underground laboratories where there is no natural wind, the threat is more intense. In this work, the ventilation design factors and potential leakage factors are identified by taking the leakage and diffusion of a large liquid nitrogen tank in China Jinping Underground Laboratory (CJPL) as an example. Based on computational fluid dynamics (CFD) research, the effects of fresh air inlet position, fresh air velocity, exhaust outlet position, leakage hole position, leakage hole size, and leaked nitrogen mass flow rate on nitrogen diffusion behavior in specific environments are discussed in detail from the perspectives of nitrogen concentration field and nitrogen diffusion characteristics. The influencing factors are parameterized, and the Latin hypercube sampling (LHS) is used to uniformly sample within the specified range of each factor to obtain samples that can represent the whole sample space. The nitrogen concentration is measured by numerical value, and the nitrogen diffusion characteristics are measured by category. The GA-BP-ANN numerical regression and classification regression models for nitrogen concentration prediction and nitrogen diffusion characteristics prediction are established. By using various rating indicators to evaluate the performance of the trained model, it is found that models have high accuracy and recognition rate, indicating that it is effective in predicting and determining the concentration value and diffusion characteristics of nitrogen according to ventilation factors and potential leakage factors. The research results can provide a theoretical reference for the parametric design of the ventilation system. [ABSTRACT FROM AUTHOR]

[Objectives]In order to solve the problem of poor ventilation areas of grain pile, the effect of the fractal structure on the ventilation uniformity in the ventilation process was explored. [Methods]A porous medium(sand)packing wrapped non-uniform section ventilation pipeline ventilation system was proposed. The relevant parameters of fractal structure were obtained by the minimum flow resistance optimization method of rectangular unit configuration. Combining the fractal branch pipelines designed according to the optimization parameters with the non-uniform section ventilation pipelines, a porous medium packing wrapped non-uniform section pipelines and fractal structure ventilation system was proposed. The grain type was selected as rice, and the porous medium material of the packing zone was selected as sand. The ventilation and cooling simulation of the two ventilation systems was carried out. The study simulated the cooling process of the granary with an initial temperature of 300 K and cold inlet air with a constant temperature of 293 K. The ventilation time lasted for 7.5 days. The ventilation velocity field, temperature field of the two ventilation systems were compared and verified. [Results]In the non-fractal ventilation system, most of the poor ventilation areas were in the packing zone, and the ventilation intensity of the grain pile was guaranteed. However, the strong ventilation and strong cooling areas were concentrated near and above the ventilation pipelines, and the cooling uniformity was not good. In the fractal ventilation system, the poor ventilation areas were suppressed under the ventilation pipelines and the fractal branch pipelines. From the velocity field, the ventilation uniformity and the cooling uniformity in the grain pile were better, and the maximum temperature difference was reduced from 2.8 K to 1.3 K. From the ventilation uniformity index, the ventilation uniformity of the fractal ventilation system was good, and exponent of uniformity was 0.919. [Conclusions]The sand packing zone could help the grain pile avoid most of the poor ventilation areas. The fractal structure could effectively enhance the ventilation intensity in the weak ventilation areas of the velocity field, and the temperature field had excellent effect in improving the uniformity of cooling. [ABSTRACT FROM AUTHOR]

Volatile organic compounds (VOCs) can cause health problems for residents and are one of the causes of sick building syndrome. Therefore, this study measured VOCs in 116 houses in the winter and 66 in the summer in Japan, including detached and apartment houses. The diffusion sampler method was used for field measurements. Living rooms and bedrooms were sampled to confirm the concentration characteristics and differences between the two locations. In addition, a questionnaire survey was conducted to identify the type of house, residence period, and type of ventilation system used. Most VOC concentrations did not exceed the Japanese guidelines during the winter and summer. However, in the winter, the acetaldehyde concentrations exceeded the Ministry of Health, Labour, and Welfare of Japan (MHLW) guidelines, reaching 14.7% in the living room and 12.9% in the bedroom. The VOC concentration was higher in apartments than in detached houses. Even among detached houses, built-for-sale houses had slightly higher VOC concentrations than custom-made houses. The concentration of VOCs according to characteristics, such as the residence period, did not show significant differences except for acetaldehyde. In houses with unbalanced ventilation, formaldehyde and other VOC concentrations were higher in the living room and bedroom than in houses with balanced ventilation.

Pre-dehumidification time (τpre) and pre-dehumidification energy consumption (Epre) play important roles in preventing the condensation of moisture on the floors of rooms that use a radiant floor cooling (RFC) system. However, there are few theoretical or experimental studies that focus on these two important quantities. In this study, an artificial neural network (ANN) was used to predict condensation risk for the integration of RFC systems with mixed ventilation (MV), stratum ventilation (SV), and displacement ventilation (DV) systems. A genetic algorithm-back-propagation (GA-BP) neural network model was established to predict τpre and Epre. Both training data and validation data were obtained from tests in a computational fluid dynamics (CFD) simulation. The results show that the established GA-BP model can predict τpre and Epre well. The coefficient of determination (R2) of τpre and of Epre were, respectively, 0.973 and 0.956. For an RFC system integrated with an MV, SV, or DV system, the lowest values of τpre and Epre were with the DV system, 23.1 s and 0.237 kWh, respectively, for a 67.5 m3 room. Therefore, the best pre-dehumidification effect was with integration of the DV and RFC systems. This study showed that an ANN-based method can be used for predictive control for condensation prevention in RFC systems. It also provides a novel and effective method by which to assess the pre-dehumidification control of radiant floor surfaces.

The distribution of velocity and temperature field inside the granary can be used to evaluate ventilation quality. A well-ventilated system with uniform air-flow and cooling can effectively prevent moisture accumulation. To address the issue of poor uniformity in ventilation and cooling, this research introduces two new ventilation systems: the non-fractal ventilation system and the fractal ventilation system. The fractal structure was designed based on optimized parameters obtained from rectangular elements with minimum flow resistance. Numerical simulation methods were employed to verify the effectiveness of these ventilation systems. A comparative analysis was conducted, examining the velocity field, temperature field, and velocity uniformity of the two systems. The results demonstrated that the presence of a sand packing zone helped the grain pile zone avoid most of the areas with poor ventilation. The discontinuous pores at the interface between the sand packing zone and the grain pile zone significantly increased flow resistance, effectively reducing the velocity of high speed ventilation into the grain pile zone and decreasing the permeability of the grain pile zone towards the poorly ventilated areas of the sand pile zone. Furthermore, the fractal structure greatly enhanced ventilation intensity in areas with poor ventilation in the velocity field, while also improving the uniformity of cooling in the temperature field. This research presents an innovative solution for ventilation in room-type warehouses, offering a new option for effective and efficient ventilation. [ABSTRACT FROM AUTHOR]

Carbon dioxide from human breath contributes significantly to airborne diseases. Breathing can expose us to usually dangerous airborne infections, which rapidly spread. By using a bus, there is a chance of contracting an infection. This study takes into account a mathematical model of airborne infection caused by human breath. The purpose of this research is to evaluate the probability that passengers in a bus with ventilation systems may well get an airborne infection. The model can be divided into five submodels, such as an exhaled air concentration measurement model for a bus with a variable number of passengers, the volume fraction of exhaled air model, the concentration of airborne infectious particles model, the number of airborne infectious particles model, and the risk of airborne infection model. The model's solution might be used to determine the probability that susceptible people will get an airborne infection. An explicit forward-time centered-space finite difference method is used to approximate the solution. In order to reduce the risk of airborne infection and improve ventilation, the provided mathematical models were used to assess the risk of airborne infection among bus passengers using ventilation systems. Better air quality control that balances the number of passengers allowed to travel on a bus will be among the ventilation's main advantages. [ABSTRACT FROM AUTHOR]

This study aimed to evaluate the effect of two circulation modes of a plasma deodorization unit on the air environment of pig-fattening houses in winter. Two pig-fattening houses were selected, one of which was installed with a plasma deodorizing device with two modes of operation, alternating internal and external circulation on a day-by-day basis. The other house did not have any form of treatment and was used as the control house. Upon installing the system, this study revealed that in the internal circulation mode, indoor temperature and humidity were sustained at elevated levels, with the NH3 and H2S concentrations decreasing by 63.87% and 100%, respectively, in comparison to the control house. Conversely, in the external circulation mode, the indoor temperature and humidity remained subdued, accompanied by a 16.43% reduction in CO2 concentration. The adept interchange between these two operational modes facilitates the regulation of indoor air quality within a secure environment. This not only effectively diminishes deleterious gases in the pig-fattening house but also achieves the remote automation of environmental monitoring and hazardous gas management; thereby, it mitigates the likelihood of diseases and minimizes breeding risks. [ABSTRACT FROM AUTHOR]

The article focuses on an analysis of the indoor climate in a small, newly-built auditorium. Providing optimal indoor climate parameters in the interiors of a university is extremely important for students. Meeting these parameters is essential not only from a physiological point of view, but also to achieve desirable student performances. The parameters of CO2 concentration are also influenced by the air distribution system in a small auditorium. The correct positions of the supply and extract air is very important. The first experimental measurements of CO2 concentration were carried out in a small auditorium in an old building. The natural ventilation of the small auditorium was evaluated. The second experimental measurements of the CO2 concentration were made in a small auditorium in a newly-built building. The ventilation system and the modern air distribution system of the small, newly-built auditorium were evaluated based on the CO2 concentration and the PMV index. A Testo 480 was used for the measurements. The conclusion of this paper contains the recommendations for the design of a newly-built ventilation system in a small auditorium.

Bacteria and viruses can travel along air currents, remain in the air, or cling to surfaces before being breathed in by another person. They are transferred by tiny respiratory droplets and are referred to as airborne infections. Lack of ventilation or low ventilation rates is associated with increased infection rates or clusters of airborne infections. While normal people remain in the same outpatient room as infectors, this research will utilize a two-dimensional mathematical model for approximating the exhaled air concentration in the specified region with an outlet ventilation system and the risk of infection. As a result, the exhaled air concentration and infection risk are affected by the initial concentration level, the distance of the seating position, and the rate of ventilation. The forward time center space technique is used to estimate the model solution. A good agreement solution is obtained using the forward time center space. The model can also be used as part of an internet of things (IoT) system to explore inventive ways to infection)free zone management. The proposed strategy represents the balance in the air quality management process between the distance of the seating position and the performance of the air ventilation system for optimal outcomes. We illustrate that the suggested technique works in real-world circumstances. [ABSTRACT FROM AUTHOR]

Air distribution system could critically affect SARS-CoV-2 transmission in indoor space; therefore, this study aims at demonstrating numerical characteristics of SARS-CoV-2 migration with varied air distribution system configurations. Seven cases were investigated regarding three major aspects: how fast suspended particles can be removed from the ventilated space or changed into deposited particles; how much particles are attached to various object surfaces which leads to an infection by touching fomite. All cases were analyzed through computational fluid dynamics (CFD). Both different shapes (round or linear diffusers) and installation locations (ceiling or floor) of inlet and outlet diffusers were investigated. Results showed that different air distribution system would lead to different dispersion profiles of infectious particles and different deposition pattern of particles on interior surfaces. With the same air flow rate, linear-diffuser would perform better for CO2 extraction while requiring less time to remove or collide the same magnitude of suspended droplets compared to round-diffuser. However, how quickly removed or suspended droplets collide is not proportional to how less the number of total particles are remained. Two additional cases with double sized space possessing best ventilation configuration were also examined to explore potential application of the best-ventilated configuration to various spatial expansion cases. [ABSTRACT FROM AUTHOR]

COVID-19 is transmitted through droplets or aerosols containing the virus, the very small particles exhaled by infected people or exposure to items infected with the virus. These droplets, aerosols and particles may be inhaled by others, or fall into their eyes, mouth and nose. In some cases, they may contaminate the contact surface. It is most likely to be infected if they are less than 1 m away from the infected person. To evaluate the effects of different air conditioning systems on the spread of human exhaled pollutants, computational fluid dynamics (CFD) was used to study the movement and diffusion of exhaled air from two rows of 12 sitting adults in a hospital's closed transfusion room. In this paper, a closed transfusion room with 12 human models was established firstly, and the mathematical model verified by experimental test results was used to study the propagation of viral aerosol particles in the enclosed space under different air conditioning systems. The result showed that when the transverse strong air flow is generated in the room, the concentration distribution of virus particles will show a roll like distribution and the personnel inside the roll will cause new infection. The air flow generated by the air conditioning system will affect the dispersion of droplets in the air. Evaluating and guiding the air flow to avoid blowing air from one person to another may reduce the risk. [ABSTRACT FROM AUTHOR]

In this study, we analyze the performance of ventilation modules to improve air quality in educational facilities. Using (CFD), we examine the flow design variables of a window-mounted ventilation module. Using computational analysis, we analyze various flow design characteristics of window-mounted ventilation modules and review optimal conditions. First, we measure the carbon dioxide concentration in the classroom and use CFD to analyze the internal air characteristics according to the ventilation module's inflow speed, inflow angle, and indoor temperature conditions. According to classroom air quality management standards, the concentration of carbon dioxide must be managed below 1000 ppm. When the ventilation module's inflow velocity was 2.0 m/s, a carbon dioxide concentration of less than 1000 ppm was measured in the classroom. Additionally, an air filter was selected to prevent the inflow of external fine dust through the ventilation module. The suitability of HEPA H14 was reviewed to design the weight concentration of fine dust flowing from the ventilation module to be less than 50 μg/m3. Through research, flow design conditions for a window-mounted ventilation module were presented to reduce carbon dioxide concentration inside the classroom. The analysis of the ventilation system flow characteristics proposed in this study derived primary data for improving the classroom ventilation system. [ABSTRACT FROM AUTHOR]

Global warming could be slowed down by removing carbon dioxide from the atmosphere, yet classical methods for carbon dioxide capture are fewly adapted to indoor settings with carbon dioxide concentrations of 1000–2000 ppmv. Here we review advanced indoor carbon dioxide capture technology with focus on physical adsorption, chemical adsorption, and materials for carbon capture. Physical adsorption includes thermal swing adsorption, ion exchange, and activated carbon impregnation. Chemical adsorption comprises wet impregnation, chemical grafting, the sol–gel method, electric mixing, the solvothermal method, and phase inversion. We observed that thermal swing adsorption is efficient, requires low energy, and is long-lasting. Wet impregnation fosters the development of high-performance materials with exceptional adsorption capacity through modifications in loading mass fraction and functionalization. Silicon dioxide is the most prevalent support material for wet impregnation, with tetraethylenepentamine and polyethyleneimine loading on silica exhibiting remarkable adsorption capacities, up to 4.05 mmol/g. Coupling of ventilation systems with indoor capture devices is promising for applications. The current research on indoor capture primarily focuses on the enhancement of adsorption capacity, thus often overlooking material stability and adsorption rates. Therefore, mathematical models are needed to optimize cyclic stability. [ABSTRACT FROM AUTHOR]

In view of the problem of high-temperature heat hazard caused by poor ventilation deep in Linglong Gold Mine, the optimization scheme of the ventilation system in Jiuqu sub-mine of Linglong Gold Mine is determined by means of field investigation, calculation of total air volume, optimal setting of fan station and newly-added ventilation shaft and roadway engineering.The research results show that through the newly excavated-470 m to-620 m level return air shaft project in Jiuqu ore block, a "two-in-three-return" ventilation mode was formed with air intake from the main shaft and auxiliary shaft, and return air from the east and west wings and the reverse section of Line 55 in the middle.At the same time, return fan stations are set at the return air shafts in the-620 m level（east wing） of Jiuqu ore block and-620 m level（west wing） of Dakaitou ore block and Line 55（central） of the-620 m level.The total air volume of the system reaches 204.7 m³/s through Ventsim 3D ventilation simulation software calculation, which can meet the requirements of deep ventilation.The research results lay the foundation for the optimization of deep mining systems. [ABSTRACT FROM AUTHOR]

AbstractThis article examines the challenges and solutions associated with protecting railway workers from the negative effects of exposure to diesel emissions and dangerous dust emissions during tunnel maintenance works. A major difficulty in this matter is the increased risk of respiratory and cardiovascular diseases for railway workers due to exposure to diesel and gasoline-powered vehicles and dangerous dust emissions, which is further compounded in enclosed spaces such as tunnels. The article analyses the feasibility of renouncing the currently imposed use of ventilation systems during certain railway maintenance work in Germany while still ensuring occupational safety of the employees. The research methodology involves a comprehensive investigation of the applicable national legislation and limit values for dangerous carcinogenic chemicals. The hypothesis is then validated by interpreting the measured values for elementary carbon and for the gases CO, CO2, NO and NO2 during a pilot project conducted in 2022. The findings indicate that it is theoretically possible to forego the technical ventilation system in certain cases of railway maintenance, such as cleaning and flushing a railway drainage located in a tunnel, without jeopardising the occupational safety of employees if an alternative and less expensive fallback measure (face masks for employees) is implemented. The implications of these findings for railway workers and rail maintenance projects are discussed. In the conclusion of the article, recommendations for conducting additional research and improving the current understanding of the topic are provided.

The gas accumulation in the return corner of a high-gas fully mechanized mining face can easily cause the gas volume fraction to exceed the safety limit, threatening the safety of coal mines. In this study, the unit method was used to analyze the gas sources and emissions based on the actual case. The airflow and gas distribution characteristics of the two-inlet-one-outlet (TIOO) ventilation system and the one-inlet-two-outlet (OITO) ventilation system were studied using CFD numerical simulation. The results show that under the TIOO ventilation system, the "U"-type air leakage in the goaf leads deep gas into the return corner, which causes the gas volume fraction in the return corner to rise to 0.4–2.0%. After the mining face is optimized into the OITO ventilation system, the "J"-type air leakage of the goaf suppresses the high concentration of gas in the deep position of the goaf. Combined with the gas extraction measures, the gas volume fraction in the return corner, exhaust roadway's outlet, and retaining roadway's outlet is controlled at 0.28%, 0.34%, and 0.23%. This study will provide new ideas for solving the problem of gas accumulation in the return corner of a high-gas fully mechanized mining face. [ABSTRACT FROM AUTHOR]

High-concentration oil mists can cause serious health problems to workers, which are generally mitigated by ventilation and purification systems. However, the coupling relationship between these systems is not clear. In this study, the effects of purifier outlet direction, purification air volume, installation height, and purification efficiency on indoor oil mist distribution were investigated by numerical simulation using an actual machining factory. The mitigation of oil mist in various combinations of ventilation and purification systems was also discussed. The results show that the outlet direction of the purifier has a great influence on the distribution of oil mist in the factory, and the maximum difference of oil mist concentration in the breathing zone under different orientations is 17%. The best purifier outlet direction is vertically upward. When the purifier outlet direction is upward, a larger purification air volume is beneficial for contaminant removal, and a lower purifier exhaust installation height is helpful for oil mist discharge from the bottom of the factory and reducing the concentration of oil mist in the breathing area. The oil mist concentration of purifier exhaust increases from 0 to 2 mg/m3 and the oil mist concentration in the breathing zone increases by 67%. The combined system of purification system with the roof exhaust system and displacement ventilation system has the optimal pollution removal efficiency and the lowest concentration of oil mist in the breathing zone compared to other systems. The research results can provide a reference for the design, installation, and operation of ventilation and purification systems in machining factories. [ABSTRACT FROM AUTHOR]

In 2020, the COVID-19 pandemic has had a huge impact on the education system in Malaysia, especially at higher education level. A number of public or private universities have carried out online learning classes due to the Covid-19 pandemic and avoid the spread of the virus among university students. Face to-face learning can not be implemented because the learning efficiency in class management decreased. Thus, this study discussed the integration of wireless sensors within the classroom, focusing on improvement of ventilation system and learning efficiency in classroom design. As a result, the goals of this research are to identify the types of wireless sensors that can be used to improve the ventilation system in classroom design, to identify the mechanisms of wireless sensors that can be used to improve the ventilation system in classroom design, and to propose design guidelines for using wireless sensors to improve the ventilation system and learning efficiency in classroom design. Reviews on related topics such as wireless sensor technology and smart classroom will be made via online searching articles and journals. Acquisition of primary data and secondary data will be done via case study of smart classroom from relevant articles and journals.

This study investigated the air quality and ventilation systems of 22 public toilets in 10 railway stations in China. Approximately 80% of public toilets meet the standard for ammonia concentration in Class I toilets, while 20% exceed the standard. It was found that the concentration of pollutants is mainly related to the number of toilet users and the ventilation system. In 20% of public toilets, the change in ammonia concentration was delayed by about 1 to 2 h with the change in hourly service number. In order to improve the air quality, a design method for calculating the number of toilet cubicles was proposed. Results show that the service capacity of the cubicle per hour (SCCH) of a female toilet is 12, the SCCH of male toilets is related to the ratio of squatting pans to urinals (RSU), which is suggested to be 1:1~1:0.8, and the corresponding SCCH is 16~20. Then, the effect of different ventilation forms was simulated by computational fluid dynamics (CFD) 2019 software. The results show that the bottom exhaust was better than the top exhaust and that the fresh air supply system is unnecessary. The recommended ventilation rate for toilets is 20 air changes per hour (ACH). The scale design method of toilets proposed in this paper was meant to address the gender imbalance and avoid queuing and provides a reference for the renovation and design of public toilets. [ABSTRACT FROM AUTHOR]

Fire tests are used to determine whether fire protection products meet the minimum performance criteria set out in codes and legislation, as well as to certify these products. Experimental large-scale fires are used to test the performance of safety systems in tunnels, which are confined environments with a high probability of accidents and significant consequences due to the evolution of the event and whether there is the capability of counteracting it by safety measures. In this study, we conducted a systematic literature review following PRISMA guidelines. We searched the Scopus and Web of Science databases for publications from 2013 to 2022, resulting in a selection of 72 articles. An analysis was conducted on the following main topics: tunnel fires, fire characteristics (measured variables, spread, and smoke), model-scale tests, automatic shutdown systems, and ventilation solutions. One of the most important contributions of this study is the suggestion that fire tests represent an effective method not only to prevent fire events in tunnels but also to ensure the resilience of the infrastructure. Based on this state-of-the-art literature review, future tunnels could be designed by linking new smart technology and artificial intelligence to create interactive and high-performing safety systems. [ABSTRACT FROM AUTHOR]

People inside a road tunnel may be in grave danger if there is a fire. When a fire is developing, mechanical ventilation can be crucial in protecting occupants and facilitating the arrival of emergency crews. In this paper, a new calculation method that can analyze the evolution of the fire and of the airflow is illustrated. An assumed fire inside an 800 m long one-way road tunnel in Northern Italy was dealt with using the developed method. Subsequently, the acquired results were successfully compared to those of numerical modeling. By varying the position of the fire inside the studied tunnel, it was then possible to detect situations of high risk for the people when the fire is located at a limited distance from the upstream entrance. The newly developed calculation procedure was then able to verify how a simple different positioning of the pairs of jet fans inside the tunnel can eliminate the risks that people intent on escaping towards the upstream entrance can be reached by the fire fumes (back-layering phenomenon). It can therefore be a useful tool to improve the jet fan design in one-way road tunnels in accordance with safety principles. [ABSTRACT FROM AUTHOR]

With frequent outbreaks of COVID-19, the rapid and effective construction of large-space buildings into Fangcang shelter hospitals has gradually become one of the effective means to control the epidemic. Reasonable design of the ventilation system of the Fangcang shelter hospital can optimize the indoor airflow organization, so that the internal environment can meet the comfort of patients and at the same time can effectively discharge pollutants, which is particularly important for the establishment of the Fangcang shelter hospital. In this paper, through the reconstruction of a large-space gymnasium, CFD software is used to simulate the living environment and pollutant emission efficiency of the reconstructed Fangcang shelter hospital in summer under different air supply temperatures, air supply heights and exhaust air volume parameters. The results show that when the air supply parameters are set to an air supply height of 4.5 m, an air supply temperature of 18 °C, and an exhaust air volume of a single bed of 150 m3/h, the thermal comfort can reach level I, and the ventilation efficiency for pollutants can reach 69.6%. In addition, the ventilation efficiency is 70.1% and 70.3% when the exhaust air volume of a single bed is continuously increased to 200 and 250 m3/h, which can no longer effectively improve the pollutant emission and will cause an uncomfortable blowing feeling to patients. [ABSTRACT FROM AUTHOR]

This study aimed to evaluate the effect of two circulation modes of a plasma deodorization unit on the air environment of pig-fattening houses in winter. Two pig-fattening houses were selected, one of which was installed with a plasma deodorizing device with two modes of operation, alternating internal and external circulation on a day-by-day basis. The other house did not have any form of treatment and was used as the control house. Upon installing the system, this study revealed that in the internal circulation mode, indoor temperature and humidity were sustained at elevated levels, with the NH3 and H2S concentrations decreasing by 63.87% and 100%, respectively, in comparison to the control house. Conversely, in the external circulation mode, the indoor temperature and humidity remained subdued, accompanied by a 16.43% reduction in CO2 concentration. The adept interchange between these two operational modes facilitates the regulation of indoor air quality within a secure environment. This not only effectively diminishes deleterious gases in the pig-fattening house but also achieves the remote automation of environmental monitoring and hazardous gas management; thereby, it mitigates the likelihood of diseases and minimizes breeding risks.

Abstract Ventilation system affects the water evaporation rate, energy consumption and the paper quality, which is considered as the largest optimization potential part of multi-cylinder dryer section. Energy consumption of drying system is divided into three parts: steam consumption of cylinders, steam consumption of air heaters, power consumption of blowers and exhaust fans. An energy consumption model of drying system integrating steam condensation system and ventilation system is constructed according to the control logic and process flow of the actual ventilation system, by combining the established models of each module and energy consumption indexes. It is the premise to realize the intelligent control of paper drying process. The research results perfects the mechanism of ventilation system for assisted drying, which can promote the improvement of the monitoring, and enable intelligent computing technology to play a greater role in optimizing drying operation and reducing drying energy consumption.

Screening clinics play a major role in preventing the transmission of infectious diseases. The main problem that should be addressed is the exposure to cross-infection between healthcare workers and individuals intended to be tested. In this study, a noncontact modular screening clinic (NCMSC) was developed that addresses the problems of existing screening clinics and the risks of cross-contamination during the infectious disease sampling process. The space and ventilation system of the NCMSC were designed to effectively remove viral aerosols to avoid cross-contamination. The spatial configurations that enabled noncontact specimen sampling and pressure differential control was achieved. Regarding the measurement method with the use of tracer gas, an experimental field test framework and procedure that can evaluate the cross-contamination between rooms were presented. It is the observation of pollutants (tracer gas) in two different modes (normal breathing and AGP from a patient) in a screening clinic with ventilation, compared to the room next door, where the HCW is located. Additionally, based on onsite experiments using SF6 tracer gas that mimics the viral aerosol at an actual scale, it was verified that no cross-contamination occurred in the NCMSC; accordingly, it was possible to protect sufficiently the healthcare workers. It will be possible to use the outcomes of this study as basic data for the development of standards for the installation and operation of screening clinics for infectious diseases.

The paper presents a 2D mathematical model for a regenerative heat exchanger designed for a ventilation system operating with a periodic swap of airflow direction. This kind of ventilation system saves the heat energy required for heating of domestic premises during a winter season. Results for calculations by a two-dimensional model are compared with one-dimensional modeling and with experimental data. The authors formulated a definition of energy efficiency in terms of the reduction of heat losses. Our calculations demonstrate that the efficiency of a regenerative heat exchanger might exceed 90 %. The numerical simulation was applied for a parametric study of this problem; we revealed the influence of the heat exchanger operational and design parameters on the energy efficiency. Numerical experiments found a group of parameters that are most significant for energy efficiency of this ventilation system; recommendations on system optimization were formulated. [ABSTRACT FROM AUTHOR]