Maximum CO2 Concentration Research Articles

Preparation of 3DOM ZrTiO4 Support, WxCeMnOδ/3DOM ZrTiO4 Catalysts, and Their Catalytic Performance for the Simultaneous Removal of Soot and NOx.

As an efficient and durable engine, a diesel engine has a broad application. However, soot particles (PM) and nitrogen oxides (NOx) coming from diesel engines are the main causes of air pollution, so it is necessary to design and prepare an effective catalyst for the simultaneous elimination of PM and NOx. In this work, a novel 3DOM ZrTiO4 support and a series of WxCeMnOδ/3DOM ZrTiO4 catalysts (where x indicates the wt% of W) were designed and fabricated by the colloidal crystal template technique. Among the as-prepared catalysts, the W1CeMnOδ/3DOM ZrTiO4 catalyst exhibits the highest NO conversion rate (52%) at the temperature of maximum CO2 concentration (474°C) and achieves 90% NO conversion in the temperature range of 250–396°C. The excellent catalytic performance is associated with the macroporous structure, abundant oxygen vacancies, sufficient acid sites, and the synergistic effect among the active components. The possible reaction mechanisms of WxCeMnOδ/3DOM ZrTiO4 catalysts were also discussed based on the characterization results.

Environmental Health Risk Assessment of Air Pollutants in Online Motorcycle Taxi Drivers in the Special Capital Region of Jakarta

Introduction: Online motorcycle taxi drivers spend most of their time outside as either driving or waiting for their customers. Therefore, chances of exposure to various air pollutants are higher and may cause various health problems, especially the respiratory problems. Methods: This is a descriptive study that used the Environmental Health Risk Analysis method to estimate the Risk Quotient (RQ) from exposure to PM10, SO2, CO, O3, and NO2 in drivers. The RQ was calculated based on exposure concentrations from the Special Capital Region of Jakarta Environment Agency; daily working hours, working days in a year, and working period obtained from interviews; additionally, body weight measurement, reference concentration (RfC), and the default value of inhalation intake were also collected. The population of this study was adult online motorcycle taxi drivers who operate around areas which become the air quality measurement stations in the Special Capital Region of Jakarta with a total sample of 81 people. Results and Discussion: The RQ for all minimum, average, and maximum concentrations of SO2, CO, and NO2 were <1. While for the average and maximum concentrations of PM10 and the maximum concentration of O3, the RQ was >1. The safe concentrations, work duration, and the number of working days also surpassed the maximum safety limit levels. Conclusion: PM10 and O3 ambient exposures are categorized unsafe for drivers. Environmental health efforts are necessary to reduce the concentration of air pollutants, and the guidelines to reduce pollutants exposure should be provided for drivers.

Bubalus bubalis Blood as Biological Tool to Track Impacts from Cobalt: Bioaccumulation and Health Risks Perspectives from a Water-Soil-Forage-Livestock Ecosystem.

Cobalt (Co) bioaccumulation, contamination, and toxicity in the soil environment, plant growth, and cattles' health are becoming a severe matter that can cause unembellished consequences in environmental safety and human health. The present research was conducted for the assurance of cobalt (Co) amassing in three forage plant species (Zea mays, Sorghum bicolor, Trifolium alaxandrium), from four ecological sites, and sewage water and in buffaloes blood was investigated. The analysis of variance showed significant differences for Co concentration in the soil and sewage water collected from all ecological sites. Meanwhile, summer and winter seasons and forage ecotypes significantly influenced the quantity of Co. The forage pastures also vary significantly in the concentration of Co in the above-ground parts. The highest Co level was present in Trifolium alaxandrium at ecological site-5. Cobalt taken from wastewater had a higher concentration in Trifolium alaxandrium during the winter. The samples which are collected from site-V and site-IV have the maximum concentration of Co because these areas receive highly contaminated water for irrigation. Cobalt tends to be bioaccumulated in the food chain and can cause serious problems in humans and animals. Bioaccumulation of cobalt in collected samples could be accredited to anthropogenic activities. Pollution load index values for all samples fell in the range below 1. The health risk index indicated the probability of health damage caused by the ingestion of contaminated fodder. An increase of Co concentration in soil, fodder, and blood owing to wastewater irrigation to crops was indicated as an outcome of this investigation. The results indicate that the Co toxicity in forage crops is attributed to Co bioaccumulation, transfer, and pollution load in the soil-water-cattle triangle. Efforts should be extended to avoid contamination of the food chain via Co-rich sewage water. Other nonconventional water resources should be used for forage irrigation.

Estimation of environmental pollutants using the AERMOD model in Shazand thermal power plant, Arak, Iran

This study aimed to estimate the environmental pollutants emitted from a thermal power plant’s chimney. The power plant emission distribution during the 8-hour and average annual periods was modeled using the AERMOD and compared with national and international standards from December 22 2019 to September 21 2020. When the use of mazut fuel, the PM10, NOX, CO concentrations as fuel burn are less than the national and international standard. The maximum CO concentration at the 8-hour time interval is 0.15, which indicates power plants have a smaller share of CO emissions in an urban environment.

Towards enabling accurate measurements of CO2 exposure indoors

Indoor climate standards recommend maximum CO2 concentration levels in rooms. At present the CO2 exposure of occupants is assessed by measurements in a room's exhaust air or near the walls. However, most often room air is not perfectly mixed and CO2 emitted in air exhaled by occupants is non-uniformly distributed. It is more reliable to assess CO2 concentration in the air inhaled by occupants by measurements in the breathing zone as close as possible to the face. In this work the importance of the location of air sampling in front of the face, the time and frequency of sampling, and the breathing mode, for the accuracy of CO2 measurements were studied. For this a breathing thermal manikin was used. The CO2 concentration in the air exhaled by the manikin was adjusted to be the same as that for an average person. The results show that synchronization of the air sampling with the inhalation period of breathing is the most accurate method. The air sampling locations positioned between the centre of the chin and the mouth, or at the left (or right) corner of the mouth, or next to and above the nostrils, are the most representative for assessing CO2 concentration in the inhaled air. The obtained results can be used for the development of wearable devices for accurate assessment of exposure to CO2 and other indoor pollution, as well as advanced air distribution methods, such as personalized ventilation that supplies clean air to the breathing zone.

Modeling NOx, CO, SO2 and PM emissions from Sabzevar cement plant using SCREEN3 software

Introduction: Nowadays, the cement industry is regarded as one of the most important air pollution industries globally. This study aimed to simulate the emission of NOx, CO, SO2, and PM pollutants caused by the Sabzevar Cement Factory chimney by SCREEN3 software. Materials and Methods: In this study, the SCREEN3 software was employed for the distribution of NOx, CO, SO2, and PM pollutants. The inputs of the model include the concentration and emission of pollutant gases, physical factors associated with the cement factory chimney, wind speed and direction, ambient temperature, and stability classes. Results: The results of this study indicated that the maximum concentrations of NOx, CO, SO2, and PM by the SCREEN3 software occurred in unstable weather conditions (B) and wind speed of 5 m.s. The highest concentrations of NOx, CO, and PM (use of gas) were at a distance of 1400 meters from the factory chimney with the rates of 0.9, 0.32, 6.2 μg.m³, respectively. Moreover, the highest concentrations of NOx, CO, SO2, and PM (using fuel oil) were predicted at a distance of 1100 m from the factory chimney with 19.5, 360, 9, and 7.9 μg.m³, respectively. A comparison of the obtained results with the standard of the Environmental Protection Agency of Iran (EPA) revealed that the concentrations of NOx, CO, SO2, and PM were not higher than the standards. Conclusion: The comparison of results with EPA standard and Iranian clean air standard showed that NOX, CO, SO2, and PM concentrations were not higher than standards during the sampling period.

Review of the assumption of ideal mixed ventilation and estimation of attendances at trade fairs in exhibition halls

During the SARS-CoV-2 pandemic, large-scale events were initially suspended categorically without consideration of ventilation technology. In this study, CO2 concentrations were measured during three trade fairs in the fall of 2021 at Messe Frankfurt with the aim of assessing air mixing and dilution of loads emitted through human respiration. 24 sensors were installed on columns near aisles, in peripheral areas and exhaust/ambient air ducts. At three positions, in addition to a height of 2 m, measurements were taken at 3.2 m height to reveal potential stratification effects. Finally, attendances were estimated based on exhaust/ambient air CO2 levels and ambient air volume flows. Results show that the maximum CO2 concentration during visiting hours never exceeded 835 ppm. Indoor air quality thus qualified as hygienically insignificant at all times. Furthermore, no stratification was detected, indicating that air was mixed well without apparent local accumulations of CO2 and thus potentially infectious aerosols within the breathing zone. Estimated mean attendance corresponds to information provided by Messe Frankfurt. Finally, results indicate that the exhaust CO2 concentration represents a good indicator to assess air quality within the occupied zone in large-scale halls, making elaborate measurements within the occupied zone obsolete. Further evaluation is needed to support this.

An augmented Cobb-Douglas production functional modeling of the impact of climate change on Teff yields in Ethiopia

The study analyzed the impacts of climate change and related factors on yields of teff crop in Ethiopia using quantitative time series data for the period 1981 – 2018. The study adopted Augmented Cobb-Douglas Production Functional model to examine the impact of climate and non-climatic factors on yield of teff in the country. The study confirmed that long-season rainfall has negative and significant impact on yields of teff. The results indicate that an increase in rainfall during long-rainfall season, the period when crop vegetative and reproductive growth is high (J-S), revealed harmful impact on the yield of teff. This witnesses that excessive rainfall affects the yield of teff crop negatively. Conversely, the regression coefficient for maximum temperature and CO2 during crop growing season in teff growing areas portrayed positive and significant (at 5 percent) impact on yield of teff, implying that a rise in maximum temperature and CO2 concentration in teff growing areas would increase the yield of teff per unit area, i.e., would affect teff yield positively. Furthermore, the estimated coefficients for land area under teff crop production has positive and significant impact on teff yields. In general, based on the validating proofs of the current study, the hypothesis stating there is ‘‘no impact of rainfall and temperature variables’’ on yield of cereal crop is rejected, signifying that changes in climate adversely affects yields of teff, wheat and maize crops.

Optimization analysis of hydrogen separation from an H2/CO2 gas mixture via a palladium membrane with a vacuum using response surface methodology

This study uses a palladium membrane to separate hydrogen from an H2/CO2 (90/10 vol%) gas mixture. Three different operating parameters of temperature (320–380 °C), total pressure difference (2–3.5 atm), and vacuum degree (15–49 kPa) on hydrogen are taken into account, and the experiments are designed utilizing a central composite design (CCD). Analysis of variance (ANOVA) is also used to analyze the importance and suitability of the operating factors. Both the H2 flux and CO2 (impurity) concentration on the permeate side are the targets in this study. The ANOVA results indicate that the influences of the three factors on the H2 flux follow the order of vacuum degree, temperature, and total pressure difference. However, for CO2 transport across the membrane, the parameters rank as total pressure difference > vacuum degree > temperature. The predictions of the maximum H2 flux and minimum CO2 concentration by the response surface methodology are close to those by experiments. The maximum H2 flux is 0.2163 mol s−1 m−2, occurring at 380 °C, 3.5 atm total pressure difference, and 49 kPa vacuum degree. Meanwhile, the minimum CO2 concentration in the permeate stream is t 643.58 ppm with the operations of 320 °C, 2 atm total pressure difference, and 15 kPa vacuum degree. The operation with a vacuum can significantly intensify H2 permeation, but it also facilitates CO2 diffusion across the Pd membrane. Therefore, a compromise between the H2 flux and the impurity in the treated gas should be taken into account, depending on the requirement of the gas product.

Ventilation conditions and their influence on thermal comfort in examination classrooms in times of COVID-19. A case study in a Spanish area with Mediterranean climate.

Current evidence and recent publications have led to the recognition that aerosol-borne transmission of COVID-19 is possible in indoor areas such as educational centers. A crucial measure to reduce the risk of infection in high occupancy indoors is ventilation. In this global pandemic context of SARS-CoV-2 virus infection, a study has been carried out with the main objective of analyzing the effects of natural ventilation conditions through windows on indoor air quality and thermal comfort during on-site examinations in higher education centers during the winter season, as this implies situations of unusual occupation and the impossibility in many cases of taking breaks or leaving classrooms, as well as the existence of unfavorable outdoor weather conditions in terms of low temperatures. For this purpose, in situ measurements of the environmental variables were taken during different evaluation tests. As the main results of the study, ventilation conditions were generally adequate in all the tests carried out, regardless of the ventilation strategy used, with average CO2 concentration levels of between 450 and 670 ppm. The maximum CO2 concentration value recorded in one of the tests was 808 ppm. On this basis, the limit for category IDA 2 buildings, corresponding to educational establishments, was not exceeded in any case. However, these measures affected the thermal comfort of the occupants, especially when the outside temperature was below 6 °C, with a dissatisfaction rate of between 25 and 72%. Examinations carried out with outside temperatures above 12 °C were conducted in acceptable comfort conditions regardless of outside air supply and classroom occupancy. In these cases, the dissatisfaction rate was less than 10%. The results obtained have made it possible to establish strategies for ventilation in the implementation of future exams, depending on the climatic conditions outside.

Pollutant and heat removal of a small fire in a cinema hall by different ventilation systems

This paper investigates the effects of chair burning on the concentration of toxic gases and heat exhaust in a cinema hall. Different ventilation systems, including displacement ventilation (DV), impingement jets ventilation (IJV), stratum ventilation (SV), and hybrid ventilation (combination of displacement and stratum ventilation) were considered in this study. Large Eddy Simulation (LES) of the turbulent flows was performed using Pyrosim software. Concentrations of the toxic gases (CO and CO2) and the heat generated by the fire in the exit doors have been discussed in detail. Concentrations of the generated toxic gases from the fire in all three systems were within the permissible safe ranges. However, among the tested systems, displacement ventilation and impingement jet had better results. Displacement ventilation could decrease the concentrations of soot by 31%, CO by 16%, and CO2 by 11% rather than stratum ventilation. The maximum concentrations of CO and CO2 were 6.35 ppm and 335 ppm, respectively, in the displacement ventilation system. For the stratum ventilation, the concentrations of CO and CO2 were reported 7.5 ppm and 370 ppm, respectively. Using the displacement and the impingement jet ventilation systems, the heat exhaust from door #1 and door #2 are, respectively, 66.6%, and 96% lower than those obtained by the stratum ventilation system.

Indoor environmental quality and global comfort: an in-field study in workspaces

The EN 16798-1 specifies the requirements to assess indoor environmental quality (IEQ) considering thermal, air quality, lighting and acoustics domains. A drawback of the standard is that it is based on an objective evaluation approach and does not account for the subjective perception. Also, the standard does not assess global IEQ nor comfort as a single index for the interaction of all the domains. This work tests the metrics proposed in the standard relating them to the occupants’ evaluations. An in-field monitoring campaign was performed in the ARPA headquarter in Aosta (Italy), acquiring quantities to be correlated with the subjective perception of IEQ gained through surveys. An insight on the possible approach to communicate IEQ and comfort feedbacks to the occupants was investigated to promote their awareness. Preliminary results show that the occupants’ perception can be predicted by adopting the approach proposed in EN 16798-1 in the case of thermal comfort, but limitations emerge about air quality, lighting and acoustics. Such result allows investigating how the environmental variables considered by the standard (e.g., the maximum sound pressure level or the maximum CO2 concentration) can be adopted as predictors of comfort, thus how new parameters and assessment methods should be introduced.

Analysis of the combustion mechanism of diesel surrogate fuel under CO2/O2 atmosphere

Closed-cycle diesel engine (CCDE) can effectively control CO2 emissions and reduce the greenhouse gas effect, but diesel fuel combustion under an atmosphere with CO2 has the problem of misfire and unclear mechanism. In order to study the CO2 impact on diesel combustion under the CO2/O2 atmosphere, a quantum chemical (QC) model of diesel surrogate fuel (DSF) is proposed, which takes into account the CO2 pyrolysis effect (CO2⇆CO+12O2) and the new reaction of OH radical generation from pyrolysis products (CO+O2+H∙→CO2+OH∙). Firstly, the active sites of the DSF molecules are predicted by average local ionization energy (ALIE) and electrostatic potential (ESP). New chemical reaction paths are obtained using ab initio theory and density functional theory combined with thermodynamic combination algorithm. The QC model is then established by sensitivity analysis and simplification of the mechanism and computational fluid dynamics (CFD) simulation of constant volume combustion chamber (CVCC.) Secondly, the CVCC experiment bench and visualization system are set up. The flame propagation at different times (1.5 ms, 1.9 ms, 2.3 ms, 2.7 ms, 3.1 ms and 3.5 ms) are captured by high-speed cameras under four different CO2 concentrations (air condition, 50%CO2 + 50%O2, 43%CO2 + 57%O2 and 35%CO2 + 65%O2). Finally, the comparison between experiment and model shows that the QC model is suitable for studying combustion characteristics of diesel fuel under CO2/O2 atmosphere. Under maximum CO2 concentration (50%CO2 + 50%O2), The maximum errors of flame combustion limit length (FCLL) and Flame longitudinal section area (FLSA) are 8.54% and 4.94%, respectively. In addition, the CO2 pyrolysis reaction and the new reaction of generating OH radicals indicate that the CO2 chemical effect can promote the combustion of diesel fuel under CO2/O2 atmosphere.

Effects of hydrogen-enriched methane combustion on latent heat recovery potential and environmental impact of condensing boilers

Decarbonization has received significant interest from the energy sector in recent years. In particular, hydrogen enrichment of fuels has been analyzed by several researchers. A side effect of hydrogen enrichment is that it increases the water vapor content in the resulting flue gas. Although this is an undesirable phenomenon in non-condensing energy systems, the higher water vapor content is an advantage in condensing boilers as more energy can be harnessed through condensation. This study analyzes the carbon emission mitigation and latent heat recovery potential of condensing boilers using a mixture of methane and hydrogen as fuel. Accordingly, analyses were performed considering hydrogen volumetric fractions ranging from 0% (pure methane) to 100% (pure hydrogen). The maximum concentrations of CO2 and CO in the flue gas were calculated using the Ostwald diagram. The characteristics of the hydrogen–methane fuel mixture, namely the partial pressure of the water vapor inside the flue gas and the dew point temperature, were investigated as well. The fuel consumption and overall energy saving potential due to the water vapor inside the flue gas were calculated considering a condensing boiler with a gross heat input of 25 kW. As NOx emissions are correlated to the adiabatic flame temperature, the latter was investigated as well. In addition to carbon emission mitigation, the results demonstrated that the condensing boiler efficiency in terms of the higher heating value increased by 1.3%, owing to the additional latent energy saved as the hydrogen volumetric fraction increased from 0% to 80%.

Gaseous air pollutants dispersion emitted from point and line sources by coupling WRF-AERMOD models (Case study: Lowshan, Guilan Province, Iran)

The cement factories in urban areas can affect the air quality of cities due to the variety of pollutants emitted from cement production processes. In the present study, the impacts of the Khazar cement factory and two transportation axes between Guilan and Qazvin provinces were investigated on the air quality of Lowshan in Guilan Province, Iran in 2019. Due to the lack of suitable meteorological data for dispersion modeling, the WRF model was used to predict the meteorological parameters. The pollutants dispersion modeling was conducted by AERMOD software and the accuracy of results was confirmed by field measurements of NO2 obtained by passive samplers. The CO and NO2 dispersion modeling results showed that the air quality of Lowshan is in an acceptable situation compared to the ambient air quality standards. So that, the maximum one-hour concentration of NO2 in most residential areas was lower than the ambient standard, and only in small parts of the areas close to line sources, the concentration value was close to the standard limits. The maximum value of annually-averaged concentration of NO2 and the maximum one-hour concentration of CO were 17 ppb and 2.5 ppm, respectively, which are much lower than the clean air standards. Further investigation showed that in the cold weather seasons, due to the less vertical displacement of air and the decrease in the boundary layer height, the concentration of pollutants in the urban environment is higher than that in the warm weather seasons. Considering the night and day time wind roses showed that despite the existence of valley-mountain structure in the city, the air quality of the city is not affected by the mountain and valley breezes and also night and day wind roses do not follow the trend of these breezes.

Inventory of pollutant emissions into the atmosphere from gas turbine installations of gas pumping units

Development of a single method for inventory of pollutant emissions from installations based on the elaboration of existing methods for calculation of air pollution is an important scientific and practical task in the field of environmental safety.
 The main purpose of the study is to test and compare models of stationary emission sources and to assess air quality based on them.
 In the inventory of pollutant emissions, the following materials are used: direct measurements, which are based on direct instrumental measurements, and calculated measurements or combinations thereof.
 According to the direct measurements of NOx and CO emissions from the operation of gas turbines at the Valley compressor station with a nominal capacity of 1 to 50 MW, we found that: the actual emissions of NO and CO increase with the average load on the installation and the time of introduction into operation and date of issue and the actual values of the maximum allowable concentration of NOx (from 100.13 to 467 mg / m) and CO (from 16.08 to 444.88 mg / m) do not exceed the permissible levels of NO-500 mg / m and CO-250 mg / m according to the instructional documents.
 Comparison of these calculation methods showed the same results, which confirms the need for their systematization with the subsequent development of a single methodology.
 The distance of 106 m, where the maximum concentration of pollution in adverse weather conditions is expected, was obtained by the calculation method of determining the surface concentration of NOx and CO emissions from the installation.
 To assess the effectiveness of the methods for inventory of pollutant emissions into the atmosphere from gas turbines, we have developed a scheme of relationship between the object being assessed for efficiency and the object being serviced. Particularly noteworthy are the results and analysis of direct measurements of NOx and CO emissions, as well as the developed scheme for linking the inventory process for pollutant emissions into the atmosphere from installations.
 The actual concentration of pollutants can be estimated by measuring the background, although in this case it is impossible to exclude the influence of other neighboring and remote emission sources on the results of the air pollution assessment. Depending on the specific task, the results of computer simulation for given parameters of the external environment can also be used to assess the actual, retrospective or prospective conditions. Future conditions can be modeled only with the help of computer simulation.
 The method of air pollutant concentration calculation for emissions of enterprises does not consider all possible features of emission sources and, in terms of passive stationary sources and cold emissions, the algorithm needs to be clarified and the justifications in the paper indicate ways to make these improvements.
 Inventory is the first stage in the strategy of air quality regulation, as it provides information for the development, justification and decision-making in regulating the activities of gas turbines to reduce adverse effects on the environment and public health.

Indoor air quality in schools in Beijing: Field tests, problems and recommendations

This study investigated indoor CO2 and PM2.5 real-time concentrations together with air temperature, humidity and air-cleaning effectiveness of 33 classrooms in 21 schools in Beijing, China by natural ventilation with air cleaners (NV system) compared to mechanical ventilation with fresh air ventilators (MV system).We found that: (1) The proportions of PM2.5 concentrations >37.5 μg/m3 when the classrooms were occupied were 28 % and 31 % in MV and NV classrooms. (2) During periods of severe ambient pollution, the averaged PM2.5 I/O ratio was 0.47. (3) The proportions of CO2 concentrations >1000 ppm when the classrooms were occupied were 40 % and 60 % in MV and NV classrooms, although we note that the maximum CO2 concentration in NV classrooms occasionally exceeded 5000 ppm. (4)The mean ventilation rate was only 1.9 L/(s⋅person) during class in NV classrooms, and the air exchange rates (AERs) for NV and MV classrooms were smaller by 58 % and 4 % during class in times of severe ambient pollution than during those days that ambient PM2.5 ≤35 μg/m3. (5) During the days close to the beginning or end of central space heating, both MV and NV classrooms had indoor air temperatures lower than the 18 °C mandated by the Chinese Thermal Comfort Standard (GB/T 17225-2017). (6) Although MV systems showed lower energy efficiency than NV systems in removing PM2.5 in classrooms, the benefits of CO2 reduction and ventilation rates increase afforded by MV systems are important. These findings can help to identify or develop a suitable ventilation system (NV or MV system) and an operating strategy in classrooms in severe ambient pollution regions.

Experimental Investigation on Diesel Fire Toxicity in a Compartment Under Different Pool Locations

The objective of this study is to investigate how the location of fire source impacts the species generation. From the standpoint of fire safety, toxicity need to be estimated from the product gases evolved under different conditions of pool fire inside the compartment. However, industries like chemical, nuclear and thermal power plants also possess fuel positions significantly above the floor level inside an enclosure. Also, marine diesel fuel storage position in the ship cabin is just above the base, which implies an elevated pool fire conditions. In the present investigation, the severity of product gases with different pan diameters (ranges from 0.2 to 0.8 m) along with diesel fuel pan elevations in terms of toxicity were analysed. In order to study the behaviour of various fuel position, a large pool diameter 0.8 m was burned in centre, corner and rear wall centre along with six different fire source elevation. Results were analysed in terms of heat release rate (HRR), ratio of CO2/CO, upper hot gas temperature, residence time of upper hot gas, CO yield, CO2 yield and fractional effective dose (FED). The maximum HRR was obtained in the range of 10 kW to 1100 kW. For large pool diameter, results of CO2/CO ratio shows exponential decay trend along with fuel pan elevation, the maximum concentration of CO increased with increase in ceiling temperature showed parabolic trend. Moreover, lower CO2/CO ratio addresses incomplete combustion and thereby leads to higher toxicity inside the compartment.

Preparation and Absorption Carbon Monoxide Properties of a Novel Flame Retardants Based Fire-Fighting Foam

The toxicity of CO threatens the life of people in the fire site. In this study, flame retardants of nano magnesium hydroxide particles and water-soluble flame retardant 8124 are used to be mixed into the aqueous film forming fire extinguishing agent (AFFF). Smoke-suppressed fire extinguishing agent was prepared in Waring-Blender mixing cup and then stirred at 3,000 r/min for 5 min. The new extinguishing agent shows a good performance of absorption of CO and reducing the flue gas temperature. The concentration of CO was decreased below 131 ppm and flue gas temperature was basically kept below 40°C, which was 367 ppm and 83.1°C less than that in free-fire. Using new extinguishing agent can effectively reduce the harm to the trapped personnel and firemen in the fire site. It was of great significance. The harm of CO concentration below 131 ppm and flue gas temperature below 40°C was low. The time to reach the maximum CO concentration and the maximum flue gas temperature was delayed, which ensures that people have more time to escape. Even if there was not enough time to escape, people will not be seriously threatened.

Evolution of grain microbiota during hermetic storage of corn (Zea mays L.)

Respiration of biotic components of the grain ecosystem generates self-modified atmospheres (oxygen reduced and carbon dioxide enriched) during hermetic storage. The effect of temperature, moisture content and modified atmospheres on the evolution of maize microbiota is not entirely known. In this study, corn grain samples were conditioned to different moisture contents (14.3, 16.5 and 18.4%) and hermetically stored in glass jars at 15, 25 and 35 °C. Grain samples were collected at different stages of modified atmosphere evolution of each experiment: T0 (O2: 21% initial concentration); T1 (O2: 10%); T2 (O2: 0%); T3 (CO2 maximum concentration stabilized). Microbiota was quantified with Petri dish counts using selective growth media for different microbial groups. Additionally, ethanol, acetic acid and lactic acid were measured for monitoring anaerobic activity. Results indicated that there was a high correlation between water activity (aw) and the time to reach anaerobiosis (R2 of 0.85), the maximum CO2 concentration (R2 of 0.86), and the reduction of filamentous fungi and bacterial counts during hermetic storage (R2 of 0.72 and 0.48, respectively). A differential behavior of the hermetic storage was observed according to aw of the grain, and a general conceptual model is offered for its understanding. It was concluded that modified atmospheres reduced or inhibited microbial growth in stored corn, and that aw was the most influential factor in the time to reach anaerobiosis, maximum CO2 concentration, and the filamentous fungi and bacterial counts reduction during hermetic storage.