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Graphene quantum dot-based sensors have demonstrated significant promise in the detection of dangerous air pollutants that harm the environment and endanger human health. The efficient trapping and separation of numerous hazardous gases from the environment have recently garnered substantial experimental and computational attention. Nitrogen doping significantly tunes the properties of graphene quantum dots and expands their potential applications. In this study, we have investigated the sensing mechanism of pristine graphene quantum dots (GQD) along with pyridinic nitrogen-doped defective graphene systems, i.e., GQD-DV/N4, for various hazardous gases, such as arsine (AsH3), hydrogen sulfide (H2S), formaldehyde (HCHO), hydrogen cyanide (HCN), and phosphine (PH3). Our study suggests that nitrogen doping in GQDs can significantly increase the adsorption strength for these hazardous gases. Our in-depth analysis proposes that adsorption is governed by the presence of hydrogen bonds between the hydrogen in the adsorbates and the nitrogen in the adsorbents. These findings should persuade scientists to rationally and methodically modify surfaces to serve as sensors for the detection of hazardous gases. [ABSTRACT FROM AUTHOR]

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In this study, a full-scale storage tank was established to investigate the potential risks of leakage accident. We have developed a series of leak scenarios that close to real accidents and have divided the ambient areas according to relevant regulations. Considering the variety and complexity of real-life accident scenarios, the presented work revealed the combined effect of source release intensity and ambient wind speed on dispersion features by classifying leakage scenarios into active or passive release. The environmental hazards in each area is evaluated under various leak scenarios. The results show that when the approaching wind speed is low, the leakage on the windward side is the most dangerous release pattern. With the increase of the wind speed, the case with jet angle perpendicular to the incoming wind produces the largest cloud volume. Top release is the least dangerous way among the studied leak scenarios. However, the results illustrate that under some release angles, the cloud volume near the tank is not sensitive to wind speed. In leak accidents, quantitatively analysis reveals that the commonly used dimensionless concentrations ( K c ) cannot be used as a suitable parameter to discuss the concentration field except under top/leeward passive release conditions. This study will be beneficial to on-site rescue and decision-making when leakage accidents occur and provide reasonable suggestions for subsequent research on the environmental impact of container leakage and the diffusion of pollutants. [ABSTRACT FROM AUTHOR]

The increasing demand to mitigate the alarming effects of the emission of ammonia (NH3) on human health and the environment has highlighted the growing attention to the design of reliable and effective sensing technologies using novel materials and unique nanocomposites with tunable functionalities. Among the state-of-the-art ammonia detection materials, graphene-based polymeric nanocomposites have gained significant attention. Despite the ever-increasing number of publications on graphene-based polymeric nanocomposites for ammonia detection, various understandings and information regarding the process, mechanisms, and new material components have not been fully explored. Therefore, this review summarises the recent progress of graphene-based polymeric nanocomposites for ammonia detection. A comprehensive discussion is provided on the various gas sensor designs, including chemiresistive, Quartz Crystal Microbalance (QCM), and Field-Effect Transistor (FET), as well as gas sensors utilising the graphene-based polymer nanocomposites, in addition to highlighting the pros and cons of graphene to enhance the performance of gas sensors. Moreover, the various techniques used to fabricate graphene-based nanocomposites and the numerous polymer electrolytes (e.g., conductive polymeric electrolytes), the ion transport models, and the fabrication and detection mechanisms of ammonia are critically addressed. Finally, a brief outlook on the significant progress, future opportunities, and challenges of graphene-based polymer nanocomposites for the application of ammonia detection are presented. [ABSTRACT FROM AUTHOR]

The green and pollution-free mining of resources has always been a research field that people have focused on. In the process of mining resources, the production of CO, SO2 and other pollutants directly affects the health of miners and the atmospheric environment in the mining area. Therefore, it is particularly important to deal with and control the polluting gases generated by mining. Taking the underground roadway of a coal mine in Hengdong City, Hunan Province, as the research object, we studied the migration law of pollutant gas there. Comsol software was used to determine the changing state of pollutant gas migration in the roadway, and a simulation model of the wind field and the pollutant concentration field in the roadway under turbulent conditions was established. The results showed that, when the air flow moved to the front face of the roadway, it generated backflow to form a counterclockwise-rotating air flow vortex. Here, the air flow stagnated, hindering the diffusion of pollutants. The gas moved with the air flow in the roadway, and the flow's velocity decreased in the middle of the roadway, causing pollutants to accumulate. The whole wind field tended to be stable at a plane 25 m from the roadway's outlet. This indicates that the middle part of the roadway is the place where the polluted gas accumulates, and it is of representative significance to study the concentration of the polluted gas in the roadway in this section. [ABSTRACT FROM AUTHOR]

Tunnels are widely used in high-grade roads, particularly in mountainous areas; however, tunnel fires often result in severe economic losses and casualties. The fire effluents produced from asphalt pavement have attracted significant research attention. The main objective of this study is to assimilate information on various aspects of bituminous mixture emissions during fires. In this study, the fume emissions of bitumen and bituminous mixtures during combustion are comprehensively reviewed and summarized. First, the test methods for fire effluents produced by bitumen and bituminous mixtures after combustion are summarized. Second, the factors influencing the fume concentration and composition are determined. In addition, different methods to reduce the emission of fire effluents are compared, particularly for the suppression of toxic gas emissions. Then, reasonable suggestions are proposed to reduce the damage caused by hazardous gases to humans and the environment. This review is beneficial for comprehensively understanding the fume emission behaviour and future research on the smoke suppression of highway tunnel asphalt pavements during fires. [ABSTRACT FROM AUTHOR]

The adsorption behaviors of hazardous gases (NO 2 and SO 2) on MoS 2 monolayer decorated by Pd n (n =1–4) clusters (Pd n -MoS 2) are investigated by first-principles calculations, and the performance of Pd n -MoS 2 gas sensors has also been studied in this work. Our results show that Pd n nanocluster can enhance the electrical conductivity of MoS 2 monolayer with band gaps of Pd n -MoS 2 (n =1–4) sharply decreased, and the adsorption performance of NO 2 and SO 2 with higher adsorption energy and larger charge transfer. Thus, Pd n -MoS 2 show higher sensitive to NO 2 and SO 2 molecules compared with pristine MoS 2. The band gaps of Pd n -MoS 2 can be further decreased upon the adsorption of NO 2 and SO 2 (except for SO 2 /Pd 4 -MoS 2), indicating Pd n -MoS 2 (n =1–3) gas sensor shows improved gas-sensitive response to both NO 2 and SO 2 , and Pd 4 -MoS 2 shows improved gas-sensitive response only to NO 2. The recovery time analysis indicates that Pd n -MoS 2 (n =1–4) is applicable to be utilized as NO 2 and SO 2 scavenger at ambient temperature, and the recovery process can be realized simply by heating. Our results indicate that Pd n -MoS 2 (n =1–4) monolayer is a favorable candidate as adsorbent for detection and removal of NO 2 and SO 2 , and also provides guidance for further study of the MoS 2 monolayer decorated by transition metal clusters. [Display omitted] • Decoration of Pd n clusters enhances the electrical conductivity of MoS 2. • Pd n clusters enhance the adsorption of hazardous gases on MoS 2. • Pd n -MoS 2 gas sensors show improved gas-sensitive response to hazardous gases compared to prinstine MoS 2. • Pd n -MoS 2 show better sensing performance towards NO 2 and SO 2 than Cu n -MoTe 2 , Au-MoTe 2 and Ta-MoSe 2 sensors. [ABSTRACT FROM AUTHOR]

Power-to-Gas technologies could play an important role in future energy systems, since they make it possible to store surplus electric energy from fluctuating renewable energy sources such as solar and wind. In Power-to-Gas concepts, the first step towards storage is the production of H 2 by electrolysis, a possible further step is methanation. The Engler-Bunte-Institute, Fuel Technology at Karlsruhe Institute of Technology is conducting research on catalytic methanation in slurry bubble column reactors, which represent a highly load flexible reactor technology. To obtain experimental data at a semi-industrial scale a methanation pilot plant was built and commissioned. The plant is equipped with various safety valves, which may release the hazardous gases H 2 , CO and CH 4 in the chemical reactor into the environment in the unintended case of overpressure, which may lead to a flammable and/or toxic cloud, threatening the safety of the workers and other humans near the plant. In this work, the safety evaluation of the accidental release in the methanation plant is performed using the numerical tool GASFLOW-MPI. Both toxicity and flammability of the hazardous gas cloud are analyzed and discussed. A local-global two-step simulation strategy, including a local computational model and a global computational model, is employed to calculate the hazardous gas dispersion efficiently and accurately. In the first step, a local detailed computational model with fine mesh is used to calculate the release mass flow through the exhaust tube and the complicated shock waves directly without any further assumption model such as the notional nozzle model. In the second step, a large-scale model with the relatively coarse mesh is chosen to efficiently predict the hazardous gas dispersion around the entire methanation plant. Moreover, the performances of two different types of exhaust pipes are compared and discussed, and the recommended exhaust pipe design is provided. The simulation results show that version B of the exhaust tubes is more recommendable from the viewpoint of safety. • The safety evaluation of accidental release in the methanation plant is performed. • Both toxicity and flammability of the hazardous gas cloud are analyzed. • A local-global two step strategy is used to predict the hazardous gas dispersion. • Performances of two different types of exhaust pipes are compared and discussed. [ABSTRACT FROM AUTHOR]

There have been studies recently on bubble-column scrubbers with low cost and high efficiency for the absorption and treatment of hazardous gases in the event of a chemical spill. Bubble columns are vulnerable to freezing at temperatures below zero because the absorbents generally do not circulate. To address this issue, this study focused on the applicability, absorbed amount, and performance of brine as an absorbent. Under three different temperatures, i.e., −5 °C, −8 °C and −10 °C we examined brine (NaCl, CaCl2, and MgCl2) by varying the concentration required at each temperature. Following the experiments, CaCl2 brine was determined as the optimal brine for its absorption performance and affordability. Based on the experimental results, the absorption performance for ammonia, ethylene oxide, and methylamine, which are hazardous and water-soluble gases among accident preparedness substances (APS), was tested by using ASEPN PLUS. Our results suggested although the efficiency dropped by about 5% to 25% when brine was used as an absorbent, it can be used at the low temperatures because the gas solubility increased with decreasing temperature. Therefore, if brine, as an alternative, is used at temperatures about 15 °C, it can operate efficiently and stably without deterioration in the absorption performance. Given our experimental results and design data on the absorbed amount and absorbent replacement period for major hazardous gases are utilized to prevent bubble columns from freezing, it can be commercially used for small and medium-sized enterprises because it can help reduce installation and operation costs.

In the United States, industrial compounds are routinely transported by rail in pressurized vessels, often near urban areas. A rupture of a vessel, for example due to a derailment, can result in the rapid release of a liquid-aerosol-gas mixture. The health consequences of such a release, especially close to population centers, are not well understood. To address this question, a series of controlled experimental releases of pressurized chlorine (Cl 2) was conducted at the Dugway Proving Ground (Dugway, Utah). Each trial consisted of the sudden breach of a tank containing at least 4,500 kg (kg) of pressurized liquid Cl 2. In this paper, we report on measured Cl 2 concentrations in three test structures downwind of the release. Based on these data, we estimate the indoor-outdoor exchange, transport through a multi-room structure, and the first-order loss rate due to reaction or sorption. This loss rate is particularly important for consequence assessment. For example, in a mobile office with a ventilation rate of about three air changes per hour, the reaction loss rate was approximately 2.5 h−1. This accounts for a nearly 20 percent reduction in toxic load to indoor occupants. Finally, the paper discusses the modeling and analysis of a typical urban hazard assessment. • In 2015 and 2016, a series of controlled release experiments of pressurized chlorine (Cl 2) was conducted. • An experiment consisted of the sudden breaching of a tank containing greater than 4,500 kg (kg) of pressurized liquid Cl 2. • The measurement of the Cl 2 plume's transport through an array of downwind structures. • This paper reports the results of an experiment that is unlikely to be conducted often. • The reaction between the gas and indoor surfaces is important for hazard and consequence assessment. • The current study found that total Cl 2 gas loss was faster than the trailer's air change rate. [ABSTRACT FROM AUTHOR]

Highlights • Nickel oxide polycrystalline nanowires are grown via hydrothermal way & calcination. • The nanosensor undergoes a thermal gradient, becoming a virtual array. • 7 hazardous gases are tested, giving each a different thermal fingerprint. • The nanosensor shows categorization (100%) and quantitative prediction (error <15%). Abstract Monitoring of hazardous gases is nowadays very important, since the urbanized environment is more subject to this kind of pollutants. Therefore, a capillary network of small gas sensors capable to check the quality of the environment is necessary. Metal oxide gas nanosensors are small economic devices that can be easily integrated in any context, however they unfortunately lack of selectivity. We present an approach using hydrothermally grown nickel oxide nanowires working at different temperatures and creating a virtual sensors array, thus exploiting the thermal fingerprints (sensor response as a function of temperature) of the gases. Using only one nanostructured material (nickel oxide) and different machine learning techniques, the system can easily discriminate any of 7 harmful gases (C 2 H 5 OH, H 2 , CO, LPG, CO 2 , NH 3 and H 2 S, all of them reducing gases) with an accuracy of 100%. Furthermore, the nanosensor also evaluates the gas concentration with an average error lower than 15%. Our results show that, exploiting thermal fingerprints from a temperature gradient, single metal oxide resistive nanosensors can efficiently discriminate specific hazardous gases. [ABSTRACT FROM AUTHOR]

Unsatisfactory sensing selectivity remains a challenging issue for zirconia-based gas sensors and severely restrains their wide application. In view of the response selectivity for the amperometric sensor can be simply controlled by the applied bias voltage, we proposed the following strategy: operating the sensor at various bias voltage and disparate response patterns is expected; through processing these response patterns with pattern recognition algorithm, response selectivity of the sensor would be further promoted. Interestingly, research results indicate that bias voltage remarkably affects the electrocatalytic activity to each examined hazardous gas and indirectly controls the sensing behavior of the resultant sensor. In combining with principle component analysis algorithm, the sensor operated at different bias voltage (− 75, 0, 35, and 75 mV) demonstrates acceptable performance in discriminating hazardous gas. Such satisfactory sensing behavior discloses the potential future of differentiating gas mixture with an amperometric gas sensor by simply adjusting the applied bias voltage. [ABSTRACT FROM AUTHOR]

Nowadays, Atomization is the need of an industrial sector for processing various sections of a typical industry. On survey it is observed that Atomization may help to increase the reliability, quality, security and reduce cost. The Wireless Sensor Actuator Network (WSAN) is the challenging technology in the field of Industrial sectors, has been proposed in this paper to monitor, detect, and control the leakage of gases. The present research work is carried out to detect and control the hazardous gas in industrial transportation system to avoid the catastrophic accidents as well as reduce effect on environment. For this purpose, Sensor Actuator Node (SA-Node) is wired about PIC 18F4550 microcontroller along with sensing and signal conditioning capabilities. The IEEE 802.15.4 standard is deployed for wireless communication. On the other hand, the control action is carried out through Coordinator SA-Node, which is capable for the electromechanical action. To synchronize the on-chip as well as off-chip peripherals, the firmware is developed realizing the concept of real time operating system. It is observed that the system works satisfactorily with great accuracy. [ABSTRACT FROM AUTHOR]

In recent years, many studies have focused on the application of advanced technology as a way to improve management of construction safety management. A Wireless Sensor Network (WSN), one of the key technologies in Internet of Things (IoT) development, enables objects and devices to sense and communicate environmental conditions; Building Information Modeling (BIM), a revolutionary technology in construction, integrates database and geometry into a digital model which provides a visualized way in all construction lifecycle management. This paper integrates BIM and WSN into a unique system which enables the construction site to visually monitor the safety status via a spatial, colored interface and remove any hazardous gas automatically. Many wireless sensor nodes were placed on an underground construction site and to collect hazardous gas level and environmental condition (temperature and humidity) data, and in any region where an abnormal status is detected, the BIM model will alert the region and an alarm and ventilator on site will start automatically for warning and removing the hazard. The proposed system can greatly enhance the efficiency in construction safety management and provide an important reference information in rescue tasks. Finally, a case study demonstrates the applicability of the proposed system and the practical benefits, limitations, conclusions, and suggestions are summarized for further applications. [ABSTRACT FROM AUTHOR]

There is very little scientific understanding of photoexcitation effect on the adsorption properties of adsorbent. The adsorption of four hazardous gases (SARIN (propan-2-ylmethylphospho-nofluoridate), methyl dichlorophosphate (MDCP), trimethyl phosphate (TMP) and hydrogen sulfide (H 2 S)) on silica surface is taken as target sample in this work. The adsorption energy order (MDCP < SARIN < TMP) in the ground state is consistent with the strength order of intermolecular hydrogen bond (inter-HB) between hydroxyl group of silica surface and hazardous gas, and the desorption order of the three gases in previous reports. However, with the adsorption energy increase of MDCP and the decrease of SARIN and TMP, this order changes remarkably to SARIN < TMP < MDCP after photoexcitation to excited state by absorbing shortwave ultraviolet irradiation. This change is opposite to the inter-HB weakening of MDCP in the first excited (S 1 ) state and the strengthening of TMP and SARIN in the second excited (S 2 ) state. This opposite change is caused by formation of intermolecular charge transfer state of MDCP and local excitation of SARIN and TMP. The H 2 S is dissociated after photoexcitation to the S 1 state. This work presents photoexcitation as a new standard for the design and detection of adsorption properties of adsorbent for its striking effect on adsorption behaviors. [ABSTRACT FROM AUTHOR]

In recent years, many studies have focused on the application of advanced technology as a way to improve management of construction safety management. A Wireless Sensor Network (WSN), one of the key technologies in Internet of Things (IoT) development, enables objects and devices to sense and communicate environmental conditions; Building Information Modeling (BIM), a revolutionary technology in construction, integrates database and geometry into a digital model which provides a visualized way in all construction lifecycle management. This paper integrates BIM and WSN into a unique system which enables the construction site to visually monitor the safety status via a spatial, colored interface and remove any hazardous gas automatically. Many wireless sensor nodes were placed on an underground construction site and to collect hazardous gas level and environmental condition (temperature and humidity) data, and in any region where an abnormal status is detected, the BIM model will alert the region and an alarm and ventilator on site will start automatically for warning and removing the hazard. The proposed system can greatly enhance the efficiency in construction safety management and provide an important reference information in rescue tasks. Finally, a case study demonstrates the applicability of the proposed system and the practical benefits, limitations, conclusions, and suggestions are summarized for further applications.

There have been studies recently on bubble-column scrubbers with low cost and high efficiency for the absorption and treatment of hazardous gases in the event of a chemical spill. Bubble columns are vulnerable to freezing at temperatures below zero because the absorbents generally do not circulate. To address this issue, this study focused on the applicability, absorbed amount, and performance of brine as an absorbent. Under three different temperatures, i.e., −5 °C, −8 °C and −10 °C we examined brine (NaCl, CaCl2, and MgCl2) by varying the concentration required at each temperature. Following the experiments, CaCl2 brine was determined as the optimal brine for its absorption performance and affordability. Based on the experimental results, the absorption performance for ammonia, ethylene oxide, and methylamine, which are hazardous and water-soluble gases among accident preparedness substances (APS), was tested by using ASEPN PLUS. Our results suggested although the efficiency dropped by about 5% to 25% when brine was used as an absorbent, it can be used at the low temperatures because the gas solubility increased with decreasing temperature. Therefore, if brine, as an alternative, is used at temperatures about 15 °C, it can operate efficiently and stably without deterioration in the absorption performance. Given our experimental results and design data on the absorbed amount and absorbent replacement period for major hazardous gases are utilized to prevent bubble columns from freezing, it can be commercially used for small and medium-sized enterprises because it can help reduce installation and operation costs. [ABSTRACT FROM AUTHOR]

Abstract: The oscillating behaviour of TGS813 and TGS203S sensors in hazardous gases such as LPG and CO was studied under the oscillating conditions of rectangular wave, applied voltage 5V, and duty ratio as 30s/(30s+20s). It was shown that the oscillating behaviour was obviously different with the two type sensors. The data features were extracted by using Fourier and wavelet transform (WT). There were some very obscure differences among the amplitudes in fast Fourier transform (FFT) under different concentrations of LPG or CO. Further FFT analysis showed that it was difficult to discriminate between 800ppm LPG and 800ppm CO because of very little difference in the frequency content. By comparison, the corresponding coefficient plots in continuous wavelet transform (CWT) were investigated, and the original signal was also decomposed into coarse approximation A1 and five detailed information D5–D1. The results showed that the WT was more appropriate than FFT for the frequency–time problem. [Copyright &y& Elsevier]

A room temperature, highly sensitive and low ppm detection sensor device is proposed through the studies on the resonance effects of the highly toxic gas, namely, sulphur dioxide, on nanomaterial-assisted sensor, which resonates at radio frequency, via dielectric constant manipulation. [Display omitted] • Resonance effects of sulphur dioxide, on nanomaterial-assisted sensor is studied. • A two-stage, rapid and low-ppm detection system in RF range is proposed. • Unit cell of complementary split-ring resonator is used for rapid and selective detection. • Sensitivity of ∼ 17.3 KHz/ppm in the range of 0–300 ppm of SO 2 is demonstrated. SOx gases are the emissions from the industrial belt, ship exhausts, burning of fossil fuels and also a product for propellants and high-energy materials. Not only are these emissions hazardous to human health, but are toxic to the environment. Due to their ozone depletion and acid raineffects, these are extremely detrimental to the sensitive ecosystem. Detection of traces of such gaseous emissions is a challenge; which has sought various solutions; however, the answer is not satisfactory, especially in terms of selectivity and low-concentration detections. Titanium dioxide nanoparticles, which are conventionally known to exhibit gas sensing properties, due to their oxygen vacancies, have been used in ourstudies to demonstrate extremely sensitive, selective and rapid detection of SOx gaseous moieties, using a resonant frequency approach. TiO 2 nanoparticles interact with entrapped SO 2 molecules to form unique signatures of SO 4 − and shift in hydroxyl group (Ti−OH), thereby generating shifts in the resonant frequency signatures of the complementary split-ring resonator (CSRR) sensor designed for430 MHz. The duly simulated CSRR unit cell sensor is designed on copper clad with FR4 substrate. The electromagnetic waves passing through the waveguide are intercepted by the resonant structure, creating distinct resonant dips at the detector. These are manipulated by the changes in the dielectric constant of the various concentrations of SO 2 -entrapped-TiO 2 nanoparticles subjected to the sensor surface. The sensor shows the sensitivity of ∼ 17.3 KHz/ppm with discrete and selective variations in the range of 0–300 ppm of SO 2 gas moieties. The two-unit device is hence demonstrated, exhibiting a room-temperature, sensitive, selective, rapid and re-usable sensor. Using effective permittivity calculations of the SO 2 -entrapped-TiO 2 nanoparticles, the sensor is duly calibrated for a probable device application. [ABSTRACT FROM AUTHOR]

In this work, we use the first-principles method to study in details the characteristics of the adsorption of hazardous NO2, NO, CO2, CO and SO2 gas molecules by pure and heteroatom (Ti, Si, Mn) modified Al60N60 nanoclusters. It is found that the pure Al60N60 cluster is not sensitive to CO. When NO2, NO, CO2, CO and SO2 are adsorbed on Al60N60 cluster'stop.b, edge.ap, edge.ah, edge.ap andedge.ah sites respectively, the obtained configuration is the most stable for each gas. Ti, Si and Mn atoms prefer to stay on the top sites of Al60N60 cluster when these heteroatoms are used to modify the pure clusters. The adsorption characteristics of above hazardous gas molecules on these hetero-atom modified nanoclusters are also revealed. It is found that when Ti-Al60N60 cluster adsorbs CO and SO2, the energy gap decreases sharply and the change rate of gap is 62% and 50%, respectively. The Ti-modified Al60N60 improves the adsorption sensitivity of the cluster to CO and SO2. This theoretical work is proposed to predict and understand the basic adsorption characteristics of AlN-based nanoclusters for hazardous gases, which will help and guide researchers to design better nanomaterials for gas adsorption or detection. [ABSTRACT FROM AUTHOR]