Search

Peak power demand strains electrical grids and increases cost of electricity generation, transmission and distribution infrastructure. Many studies have examined ways of reducing this peak power demand, including modification of room air temperature setpoints or the reduction of lighting levels. However, very few or no studies have examined the peak power reduction resource offered by temporary curtailment of building ventilation systems. For this reason, we conducted a simulation campaign in which we examined the resource offered by temporary ventilation curtailment in commercial buildings of different use types across the United States and in residences in the state of California, with the essential constraint that any changes resulted in air quality acceptable to occupants through additional ventilation to compensate for the curtailment. To do this, we employed previously validated building models implemented in the airflow and contaminant transport tool CONTAM and building thermal and systems modeling tool EnergyPlus, in some cases co-simulated. Results show savings are highly dependent on building type and climate but range from 0-2 W/ft2 and up to 40% of total peak building power demand. Depending on building type, this power shed can be conducted for 1.5-8 hours before acute exposure or odor concerns are expected, assuming a safety factor of 2. This reduction is of the same magnitude as that offered by thermal control strategies such as setpoint increase, or from lighting reduction strategies.

An indoor thermal environment is affected by various heat elements, such as heat transfer through walls, solar radiation, and heat emissions from people, lighting and equipment. To promote both local thermal comfort and building energy efficiency, demand-oriented ventilation (such as personalized ventilation) has been developed. When using this method, a good understanding on indoor temperature distribution becomes necessary. For this purpose, an index known as Contribution Ratio of Indoor Climate (CRI) has been developed through extraction from the calculation results of Computational Fluid Dynamics (CFD). This index can be used to analyze the independent contribution of each heat element to indoor temperature distribution. In this paper, a complete and detailed introduction of the CRI is given, including its basic premises, definitions, and mathematical meaning. Particularly, calculation method of the CRI in natural convection airflow fields is further developed. Two cases (forced and natural convection airflow fields) have been carried out in different scenarios, with results showing that the CRI of a heat source had higher values in the area around itself. Also, it had a larger influence range in forced convection airflow field because of the convective airflow, while relatively larger CRI values only appear in the area above the heat source in the natural convection airflow field because of the heat plume. As a useful index for understanding the form of indoor temperature field, the CRI has guiding significance for regulating air-conditioning/ventilation systems to build better indoor thermal environment.

Mechanical Ventilation with Heat Recovery (MVHR) systems are gaining increasing interest in buildings with low energy demand, for improvement of the Indoor Air Quality (IAQ) and reduction of the ventilation energy loss. In retrofitted buildings, MVHRs are often integrated with an additional air heater to cover space heating demand. Hence, evaluation of the interactions between MVHR and heat emitter, and their effects on indoor airflow characteristics is of significant importance. The present study aims to investigate effects of a combined MVHR-fan-coil system in heating mode on IAQ and thermal comfort parameters inside a retrofitted room, by means of a computational fluid dynamic (CFD) code. The proposed CFD model is validated by comparing the numerical results with experimental data. The results yielded by numerical simulations allow evaluating the indoor environmental quality characteristics as well as addressing the MVHR and fan coil interactions. The results indicate that the airflow discharged from the fan coil could have a significant impact on the age of the air; while it provides a desirable thermal comfort condition within the room, it may hinder to some extent delivery of the fresh air to the occupied zone due to creation of counterflow fields. Furthermore, it is shown that although increasing the fan speed (ON mode) would slightly enhance the air change efficiency, the OFF mode yields not only a better distribution of the fresh air but also a higher ventilation efficiency than when fan coil operates.

The use of a metofluthrin-impregnated spatial repellent device (MSRD) is a new and effective method for preventing mosquito blood feeding. Indoor environmental factors such as room temperature and ventilation rate are thought to be important for MSRD activity. Measurements of room temperature and vaporization of metofluthrin from MSRD in typical rural metal-roof and thatched-roof houses in southeastern Malawi were conducted. The relationship between house structure and the number of collected Anopheline mosquitoes with and without MSRD treatment was also investigated. The difference between daytime and nighttime room temperature was significantly higher in metal-roof houses than in thatched-roof houses. The vaporization of metofluthrin from the MSRD was not accelerated by the high room temperature, but by the high indoor air flow by ventilation. The number of mosquito collections was significantly higher in thatched-roof houses than in metal-roof houses. MSRD-treated thatched-roof houses have a higher probability of mosquito infestation, but the vaporization of metofluthrin is also higher because of indoor air flow, resulting in a reduction in mosquito numbers. Metal-roof houses with closed eaves reduce the probability of mosquito invasion, and a longer predicted effectiveness occurs with MSRD because of the controlled release of metofluthrin through lower indoor air flow., Japanese Journal of Infectious Diseases, 75(3), pp. 288-295; 2022

AimTo describe the nature and causes of reported patient safety incidents relating to care in the community for children dependent on long-term ventilation with the further aim of improving safety.MethodsWe undertook an analysis of patient safety incident data relating to long-term ventilation in the community using incident reports from England and Wales’ National Reporting and Learning System occurring between January 2013 and December 2017. Manual screening by two authors identified 220 incidents which met the inclusion criteria. The free text for each report was descriptively analysed to identify the problems in the delivery of care, the contributory factors and the patient outcome.ResultsCommon problems in the delivery of care included issues with faulty equipment and the availability of equipment, and concerns around staff competency. There was a clearly stated harm to the child in 89 incidents (40%). Contributory factors included staff shortages, out of hours care, and issues with packaging and instructions for equipment.ConclusionsThis study identifies a range of problems relating to long-term ventilation in the community, some of which raise serious safety concerns. The provision of services to support children on long-term ventilation and their families needs to improve. Priorities include training of staff, maintenance and availability of equipment, support for families and coordination of care.

The objective of this study is to develop a modelling method for optimizing the design of a solar chimney integrated solarium to maximize the ventilation rate in the solarium. A thermal model is developed and implemented in SIMULINK to simulate the thermal response of the solarium combined with a solar chimney based on the first principle of thermal engineering. Thermal simulations are performed for critical summer days. The greenhouse air temperature and its ventilation rate with various geometrical configurations are calculated on the basis of solar irradiance intensity and ambient temperature. The preliminary numerical simulation results show that a solar chimney, combined with an appropriately inclined roof of a solarium, would be a better option for ventilation improvement in the solarium. The solarium height and solarium/solar chimney cross section areas are the critical parameters. The combination of a shorter solar chimney with a high solarium would be suitable for Toronto.

Blood oximetry provides a fundamental approach to blood gases for inpatients. Arterial blood gases (ABG) have been considered the gold standard for blood oximetry assessment. Venous blood gas (VBG) evaluation is frequently available and provides a source of a more comfortable method for the assessment of blood oximetry in pediatric patients. Some data provided by the venous blood gas can be additive and offer insights apart from the arterial blood gas. The purpose of this review is to provide an assessment of the performance of VBG in pediatric patients. The study concludes that VBG are helpful tools in assessing oxygenation and ventilation in critically ill children and can be used as a marker of adequacy of systemic oxygen delivery. In the setting of systemic oxygen delivery decrease or oxygen extraction increase, the partial pressure of oxygen on the VBG will decrease. Thus, the partial pressure of oxygen and the corresponding venous saturation can be a marker of systemic oxygen delivery in a variety of illnesses. Simultaneous ABG and VBG comparison can actually lend great insight to not only the respiratory status of a patient but provide an assessment of the adequacy of cardiac output and systemic oxygen delivery.

Evaluation of gas hygrometry allowed an improvement and progressive diversification of the humidification devices used. The main techniques to evaluate the performances of the heat and moisture exchangers (HME) and of the heated humidifiers (HH) in terms of humidification are mainly used within the framework of research. The technique of visual evaluation of condensation on the flex-tube or on the humidification chamber’s wall is feasible at the patient bedside but has several limitations. Many techniques to measure the moisture of gases exist. The most frequently used in the clinical setting are the psychrometric method and the capacitance hygrometers usable on patients (during invasive or non-invasive ventilation) or on benches. Gravimetry (used by the standard ISO 9360) has technical limitations and can be used only on bench. Psychrometry and gravimetry are generally used for clinical research, whereas the manufacturers of the humidification systems often use gravimetry.

Objective: To evaluate current practices of tracheostomy in children regarding the ideal timing of tracheostomy placement, complications, indications, mortality, and success in decannulation. Source of data: The authors searched PubMed, Embase, Cochrane Library, Google Scholar, and complemented by manual search. The guidelines of PRISMA and MOOSE were applied. The quality of the included studies was evaluated with the Newcastle-Ottawa Scale. Information extracted included patients’ characteristics, outcomes, time to tracheostomy, and associated complications. Odds ratios (ORs) with 95% CIs were computed using theMantel-Haenszel method. Synthesis of data: Sixty-six articles were included in the qualitative analysis, and 8 were included in the meta-analysis about timing for tracheostomy placement. The risk ratio for “death in hospital outcome” did not show any benefit from performing a tracheostomy before or after 14 days of mechanical ventilation (p = 0.49). The early tracheostomy before 14 days had a great impact on the days of mechanical ventilation (-26 days in mean difference, p < 0.00001). The authors also found a great reduction in hospital length of stay (-31.4 days, p < 0.008). For the days in PICU, the mean reduction was of 14.7 days (p < 0.007). Conclusions: The meta-analysis suggests that tracheostomy performed in the first 14 days of ventilation can reduce the time spent on the ventilator, and the length of stay in the hospital, with no effect on mortality. The decision to perform a tracheostomy early or late may be more dependent on the baseline disease than on the time spent on ventilation.

Summary The expense of creating exhaust ventilation in a gross anatomy laboratory can be an impediment to gross anatomical education, especially in locations with little availability of funds (e.g., developing countries). Thus, the need for inexpensive yet effective exhaust ventilation is important for gross anatomical education. This study details the creation of a downdraft ventilation table that cost less than 200 USD to build, was built with commonly available materials (i.e., lumber, tarps, rebar, corrugated steel, staples, and screws), was built by one person with little difficulty in a matter of hours, was relatively light weight (75.2 kg fully-assembled), and was easy to transport. Further, the table was structurally sound and handled a load of at least 331 kg without damage. The table was affixed to a simple local exhaust ventilation system that cost ∼300 USD and generated an exhaust flow of 3099 m3/h from the table. The table was capable of removing all airborne formaldehyde (0.00 ppm) despite a pool of 100% formalin placed 20.3 cm above the table. Furthermore, the height of the table could easily be adapted for handicapped accessibility and for individuals who are shorter or taller than average. The downdraft system also has applications beyond the gross anatomy laboratory (e.g., exhaust ventilation for embalming, manufacturing, and clinical/surgical aerosol-generating procedures). This report represents a proof-of-concept: a downdraft table that costs less than 200 USD can be built easily and paired effectively with an inexpensive local exhaust ventilation system at a total expense of approximately 500 USD. This report marks an improvement in gross anatomy laboratory safety and accessibility.

BACKGROUND Effective design and operation of Intensive Care Unit (ICU) ventilation systems is important to prevent hospital-acquired infections. Air purifiers may contribute to that. AIM In this study we aimed at detecting the number and types of microorganisms present in the air and on the high touch surfaces in the ICU; evaluating the effectiveness of the air purifying device in reducing the microbial load and thus the rate of nosocomial infections in the ICU. METHOD This interventional study was conducted in two similar ICUs between December 2019 and May 2020. Novaerus brand air purifiers were located in the "intervention ICU" for two months. Routine cleaning procedures and HEPA filtered ventilation continued in "control ICU" as well as in the "Intervention ICU". After two months the units were moved to the other ICU for the next two months to reduce any possible bias in the results. Air and surface samples were evaluated. FINDINGS The evaluation of the change in the interventional ICU over time revealed a significantly lower colony concentration in the air and on surfaces on Day 60 compared to Day 1 (pair

The level of airborne microbial contamination in operating rooms (ORs) is an important indicator of indoor air quality and ensures a clean surgical environment. It is necessary to research how different factors affect the colony forming unit (CFU) level during surgery in a mixing ventilation (MV) operating room (OR) to fulfil an ultra-clean air requirement. The main objective of this study is to clarify the possibility of achieving the requirement for an ultraclean operating room (≤ 10 CFU/m3) with mixing ventilation from two factors of clothing and human activities. The experiment results verified that the average CFU/m3 of three of five mock-up surgeries was 8.5 which was below or equal to the ultra-clean requirement, while the other two mock-up surgeries did not meet the ultra-clean requirement. Surgical activities together with clothing level of surgical staff in ORs seem to be the most significant reason for the high CFU level during surgery. It is possible to achieve the ultraclean air requirement (≤ 10 CFU/m3) during a surgical process with proper clothing and low surgical activities in ORs. This study clarifies the effect of clothing and human activities on the CFU level in the surgical microenvironment in ORs and contributes to developing new code of products for the surgical team.

Background: During general anesthesia, mechanical ventilation can cause pulmonary damage through mechanism of ventilator-induced lung injury, which is a major cause of post-operative pulmonary complications, which varies between 5 and 33% and increases the 30-day mortality of the surgical patient significantly. Objective: The aim of this review is to analyze different variables which played a key role in the safe application of mechanical ventilation in the operating room and emergency setting. Method: Also, we wanted to analyze different types of the population that underwent intraoperative mechanical ventilation like obese patients, pediatric and adult population and different strategies such as one lung ventilation and ventilation in trendelemburg position. The peer-reviewed articles analyzed were selected according to PRISMA (Preferred Reporting Items for Systematic reviews and Meta-Analyses) from Pubmed/Medline, Ovid/Wiley and Cochrane Library, combining key terms such as: “pulmonary post-operative complications”, “protective ventilation”, “alveolar recruitment maneuvers”, “respiratory compliance”, “intraoperative paediatric ventilation”, “best peep”, “types of ventilation”. Among the 230 papers identified, 150 articles were selected, after title - abstract examination and removing the duplicates, resulting in 94 articles related to mechanical ventilation in operating room and emergency setting that were analyzed. Results: Careful preoperative patient’s evaluation and protective ventilation (i.e., use of low tidal volumes, adequate PEEP and alveolar recruitment maneuvers) has been shown to be effective not only in limiting alveolar de-recruitment, alveolar overdistension and lung damage, but also in reducing the onset of Pulmonary Post-operative Complications (PPCs). Conclusion: Mechanical ventilation is like “Janus Bi-front” because it is essential for surgical procedures, for the care of critical care patients and in life-threatening conditions, but it can be harmful to the patient if continued for a long time and where an excessive dose of oxygen is administered into the lungs. Low tidal volume is associated with a minor rate of PPCs and other complications and every complication can increase the length of Stay, adding cost to NHS between 1580 € and 1650 € per day in Europe and currently the prevention of PPCS is the only weapon that we possess.

The rotor temperature rise of high voltage line-start solid rotor permanent magnet synchronous motors (HVLSSR-PMSMs) may be too high while operating, which properly causes thermal demagnetization for permanent magnets. Therefore, it is necessary to perform the thermal investigation on HVLSSR-PMSM. In this article, a 315-kW, 6-kV HVLSSR-PMSM with the air-cooled hybrid ventilation system is studied in the view of thermal phase. The losses, obtained from the electromagnetic analyses, are applied to the thermal investigation as the distributed heat sources. Whereas, both the mathematical and the geometrical models are proposed for the three-dimensional (3-D) fluid-thermal coupled investigation, from which the fluid velocity and the temperature in motor different components are determined. Whereas, with the hybrid ventilation system, temperatures in motor different components reduce, obviously comparing with those in motor with the original cooling system. The experimental investigations are performed on prototypes in both cases, which verify the calculation results and approve the effectiveness of the proposed hybrid air cooling system as well.

The mechanical power (MP) is the energy delivered into the respiratory system over time. It can be computed as a direct measurement of the inspiratory area of the airway pressure and volume loop during the respiratory cycle or calculated by "power equations". The absence of a bedside computation limited its widespread use. Recently, it has been developed an automatic monitoring system inside of a mechanical ventilator. Purpose Our aim was to investigate the repeatability and the accuracy of the measured MP at different PEEP values and tidal volume compared with the calculated MP. Material and methods MP was measured and calculated in sedated and paralyzed ARDS patients at low and high tidal volume, at 5-10-15 cmH2O of PEEP both in volume and pressure-controlled ventilation. The same measurements were performed twice. Results Fifty ARDS patients were enrolled. MP was measured and calculated for a total of 300 measurements. The bias and limits of agreement were 0.38 from -1.31 to 2.0 J/min. The measured and calculated MP were similar in each ventilatory condition. Conclusions The mechanical power measured by a new automatic real time system implemented in a mechanical ventilator was repeatable and accurate compared with the computed one.

Residents tend to close the doors and windows of their residential kitchens in severe cold conditions, making insufficient outdoor air supply and aggravating indoor air pollution. In order to understand the ventilation and pollution status of the residential kitchens in a severe cold region and improve the ventilation system, this study used questionnaires, on-site tests, and Computational Fluid Dynamics (CFD) simulation to analyze a pollution and ventilation case in Shenyang, China. The method of using ceiling openings to compensate for outdoor air supply was proposed and optimized to improve air distribution in the residential kitchen. The average CO2 concentration in the breathing region, air velocity, and temperature levels in the kitchen, before and after the improvement, were compared. The results indicated that the kitchen pollution in severe cold area of Shenyang is serious, and the ventilation habit has regional characteristics. Furthermore, the overall kitchen environment including air velocity, temperature, pollutant levels, static pressure, CO2 concentration, indoor airflow fluctuation, and cooking fire were obviously improved for the ceiling make-up air cases. These findings provide a basis for improving the reasonable air distribution of residential kitchens in cold regions and for building a thermally comfortable environment.

In order to effectively purify the diesel particulate matter (DPM) emitted by the trackless rubber wheel car in coal mining under the premise of dust control. This paper comprehensively investigated the laws of dust and DPM diffusion under forced ventilation and mixed ventilation and under different air intake volumes of the dust removal fan Q and different distances between the extractive air duct outlet and the head L by means of CFD numerical simulation. The following conclusions were drawn. Under mixed ventilation (Q=450 m3/min) dominated by forced ventilation, when L=5 m, the overall control effects on low-concentration dust, high-concentration dust and DPM are the best, with the diffusion distances being 46 m, 62 m and 54 m. Under mixed ventilation (Q=750 m3/min) dominated by exhaust ventilation, when L=5 m, the overall control effects on low-concentration dust, high-concentration dust and DPM are the best, with the diffusion distances being 23 m, 24 m and 39 m, respectively. Therefore, under the above two air volumes, when L=5 m, the best control effects can be achieved on dust and DPM in the working face.

The aero engine turbine rotors are under strong centrifugal load and the highest thermal load. The ventilation openings on the rotors are inevitable, because air flow need to pass through them to cool the temperatures down and keep the air pressure balanced in internal aero engine. The ventilation openings will lead to stress concentration effect. In this paper, the stress concentration factor of elliptical opening on rotating disc is deduced by superposition method. How to define the optimal location and shape of the elliptical opening on rotating disc to decrease the stress concentration effect has been investigated specifically. The reliability and accuracy of the theoretical deviation process is verified by Finite Element Method (FEM). The process of how to obtain the optimal location of the elliptical ventilation opening with particular shape on turbine sealing disc is described as an engineering application case. The investigation provides sufficient theoretical support for optimal location and shape definition of elliptical ventilation opening on aero engine rotors with stress concentration effect by pure mechanics consideration.

Summer days are quite difficult to live in a non-ventilated house, thus most people choose for air conditioning or air coolers at home, which consumes electricity, money, and other resources. In this research paper, you will learn about the HVAC (Heat, Ventilation, and Air-conditioning) system, which is a revolutionary means of producing air conditioning by utilising natural resources such as wind and sunlight. The component required for this system is readily available. The maintenance is free, and it may be mounted on the roof of a house or elsewhere in the garden. Because the energy used in this system is freely available in nature, it is absolutely free and extremely efficient.

One of the major effects of the COVID-19 pandemic within nuclear medicine was to halt performance of lung ventilation studies, due to concern regarding spread of contaminated secretions into the ambient air. A number of variant protocols for performing lung scintigraphy emerged in the medical literature which minimized or eliminated the ventilation component, due to the persistent need to provide this critical diagnostic service without compromising the safety of staff and patients. We have summarized and reviewed these protocols, many of which are based on concepts developed earlier in the history of lung scintigraphy. It is possible that some of these interim remedies may gain traction and earn a more permanent place in the ongoing practice of nuclear medicine.

The bacteria or virus from an infected source can transmit through the airflow in an enclosed space. The risk of such transmission is more in the operation theatres of healthcare units where the various kind of surgeries takes place and several people from the healthcare field come in the contact of open wounds or body parts of patients. Various measurements are taken to prevent such transmission, such as PPE kits, UV devices, filters of higher efficiency, etc. However, all the stated preventive measurements are found inefficient to avoid the transmission of such airborne bacteria. The adoption of different types of ventilation systems is also studied in the literature to prevent bacteria transmission. Based on the presented comparative study on the different ventilation systems, the temperature control airflow ventilation system is found as most suitable in the hospital, specifically in the operating theatres. A temperature control airflow ventilation system is an efficient approach to disinfect the contaminants in the operating room, with low energy consumption as compared to the laminar airflow and mixed airflow ventilation systems.

Objective High tidal volume ventilation is associated with ventilator-induced lung injury. Early introduction of lung protective ventilation improves patient outcomes. This study describes ventilator management during critical care transport and the association between transport ventilator settings and ventilator settings in the intensive care unit (ICU). Methods This was a retrospective review of mechanically ventilated adult patients transported to an academic medical center via a critical care transport program between January 2018 and April 2019. Ventilator settings during transport were compared with the initial and 6- and 12-hour postadmission ventilator settings. Results Three hundred eighty patients were identified; 114 (30%) received tidal volumes > 8 mL/kg predicted body weight at the time of transfer. The transport handoff tidal volume strongly correlated with the ICU tidal volume (Pearson r = 0.7). Patients receiving high tidal volumes during transport were more likely to receive high tidal volumes initially upon transfer (relative risk [RR] = 4.6; 95% confidence interval [CI], 3.3-6.5) and at 6 and 12 hours after admission (RR = 2.6; 95% CI, 1.8-3.8 and RR = 2.7; 95% CI, 1.7-4.3, respectively). Conclusion Exposure to high tidal volumes during transport is associated with high tidal volume ventilation in the ICU, even up to 12 hours after admission. This study identifies opportunities for improving patient care through the application of lung protective ventilation strategies during transport.

With the spreading of the green environmental protection concept, increasing attention has been paid to improving the tunneling environment. In this paper, the distribution characteristics of airflow fields, the diffusion laws of pollutants, and the influence of airflow rate changes on pollutants in tunnels under single-forced ventilation conditions were simulated according to the computational fluid dynamics (CFD) theory. In addition, the reliability of the simulation results was verified through field measurements. A three-stage distribution was observed once the dust concentration stabilized: we noticed areas with relatively low dust concentrations ( 500 mg/m3), and medium dust concentrations (~400 mg/m3, near the tunnel exit). Meanwhile, after stabilizing, the gas concentration was 0.67%. Properly increasing the airflow rate (Q) can effectively improve the tunnel environment: when Q reached 600 m3/min, the air in the tunnel was effectively purified. However, under a continuous increase of the airflow rate, there is a risk of pollution rebound.We conclude that, to effectively improve the tunnel environment and achieve a sustainable utilization of resources, the optimal operation airflow rate should be 600 m3/min.

Uniform ventilation is important for the safety of long tunnel in underground buildings, it is difficult to install the large size air duct to ensure the centerline of each cross-section of the traditional variable cross-section ventilation system(VCVS) superimposed on the same horizontal axis, which is significant to the ventilation uniformity, energy consumption and installation convenience of the VCVS. On the contrary, each cross-section of the Equal Cross-section Ventilation System (ECVS) has the same horizontal axis, therefore, it is more convenient to manufacture and install the large size air duct in the underground long tunnel and achieve uniform ventilation. This study proposes an ECVS, using computational fluid dynamics(CFD) numerical simulation analyzed the influences of main duct velocity, aspect ratio, and outlet numbers on uniformity and energy consumption per unit air volume(ECPV). It revealed that when each ventilation equalizer's valve Angle β is given, uniformity of air supply decreases slightly with an increase in the inlet velocity. When the air supply main duct aspect ratio increases, the outlet velocity standard deviation range is from 0.22 to 0.34. When outlet numbers N=7~12 and β are constant, air supply uniformity and resistance coefficient ξ also decrease with the decrease of outlet numbers. The outlet number has a significant influence on the uniformity of system air supply, main duct velocity, and aspect ratio are relatively small. ECPV is positively correlated with the main duct velocity and outlet number, and is negatively correlated with aspect ratio.

The transmission of coronavirus disease 2019 (COVID-19) has presented challenges for the control of the indoor environment of isolation wards. Scientific air distribution design and operation management are crucial to ensure the environmental safety of medical staff. This paper proposes the application of adaptive wall-based attachment ventilation and evaluates this air supply mode based on contaminants dispersion, removal efficiency, thermal comfort, and operating expense. Adaptive wall-based attachment ventilation provides a direct supply of fresh air to the occupied zone. In comparison with a ceiling air supply or upper sidewall air supply, adaptive wall-based attachment ventilation results in a 15%–47% lower average concentration of contaminants, for a continual release of contaminants at the same air changes per hour (ACH; 10 h–1). The contaminant removal efficiency of complete mixing ventilation cannot exceed 1.0. For adaptive wall-based attachment ventilation, the contaminant removal efficiency is an exponential function of the ACH. Compared with the ceiling air supply mode or upper sidewall air supply mode, adaptive wall-based attachment ventilation achieves a similar thermal comfort level (predicted mean vote (PMV) of –0.1–0.4; draught rate of 2.5%–6.7%) and a similar performance in removing contaminants, but has a lower ACH and uses less energy.

The research presents a simulation model of a hybrid cooling and passive ventilation system by using the ANSYS FLUENT 19.2 program. The system consists of two floors, each floor contains a room of 1 m3 connected to a vertical solar chimney 3 m long towards the south, Each room is connected to a northward evaporative cooler with a volume of 0.054 m3. The air entering the evaporative cooler comes from the earth air heat exchanger with a length of 17 m and a depth of 3 m under the soil. The solar chimney represents the passive ventilation system, while the earth air heat exchanger and the evaporative cooler represent the hybrid cooling system. The model is simulated for the climatic conditions of the city of Kut, Iraq. In this study, we will study the effect of several factors (ambient temperature, relative humidity, solar radiation intensity, soil temperature and ventilation). The results showed that the use of this system reduces the average temperature inside the rooms by 10–15 °C and maximum ventilation rate (ACH) was 13.8 and the relative humidity increased by 20% compared to the surrounding relative humidity.

A novel dual source vapor injection heat pump (DSVIHP) using exhaust and ambient air is proposed. The air exhausted from the building first releases energy to the medium-pressure evaporator and is then mixed with the ambient air to heat the low-pressure evaporator. A vapor injection (VI) compressor of two inlets is connected with the low and medium pressure evaporators. It's first time that a VI compressor is employed to recover the ventilation heat. The system can minimize the ventilation heat loss and provide a unique defrosting approach by using the exhaust waste heat. Fundamentals of the proposed DSVIHP are illustrated. Mathematical models are built. Both energetic and exergetic analyses are carried out under variable conditions. The results indicate that the DSVIHP has superior thermodynamic performance. The superiority is more appreciable at a lower ambient temperature. It has a higher COP than the conventional vapor injection heat pump and air source heat pump by 11.3% and 23.2% respectively at an ambient temperature of -10 °C and condensation temperature of 45 °C. The waste heat recovery ratio from the exhaust air is more than 100%. The novel DSVIHP has great potential in the cold climate area application.

Made available in DSpace on 2022-04-29T08:37:58Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-01-01 Background: The possibility of accurately and continuously measuring arterial oxygen partial pressure (PaO2) in horses may facilitate the management of hypoxaemia during general anaesthesia. Objectives: The aim of this study was to evaluate the ability of a novel fibreoptic sensor to measure PaO2 (PaO2Sensor) continuously and in real time in horses undergoing ventilatory manoeuvres during general anaesthesia. Study design: In vivo experimental study. Methods: Six adult healthy horses were anaesthetised and mechanically ventilated in dorsal recumbency. A fibreoptic sensor was placed in one of the facial arteries through a catheter to continuously measure and record PaO2Sensor. After an alveolar recruitment manoeuvre, a decremental positive end-expiratory pressure (PEEP) titration using 20-minute steps of 5 cm H2O from 20 to 0 cm H2O was performed. An arterial blood sample was collected at 15 minutes of ventilation at each PEEP level for PaO2 measurement using an automated blood gas machine (PaO2Ref). The agreement between PaO2Sensor and PaO2Ref was assessed by Pearson's correlation, Bland-Altman plot and four-quadrant plot analysis. In the last minute of ventilation at each PEEP level, a slow tidal inflation/deflation manoeuvre was performed. Results: The mean relative bias between PaO2Sensor and PaO2Ref was 4% with limits of agreement between −17% and 29%. The correlation coefficient between PaO2Sensor and PaO2Ref was 0.98 (P

This article presents the results of a theoretical study of the infl uence the outside air infi ltration through the enclosing structures of the walls on the amount the air’s exchange in low-rise residential buildings. Based on the information analysis from offi cial documents of state statistical and analytical bodies, the most frequently used external wall structures in modern low-rise residential construction have been determined. Based on the provisions analysis of modern regulatory documents in the construction’s fi eld, the minimum values the required air exchange were determined and the calculations of the values the infi ltration air fl ow through the outer walls for various premises of low-rise residential buildings were made. Based on the results of the analysis and calculations was made a generalizing conclusion that for the considered premises of modern low-rise residential buildings, at the expense of the infi ltration of outside air through the enclosing structures of the walls, it is impossible to provide even 20 % of the minimum air exchange.

The systemic challenges in providing safe anesthesia, including safe ventilation, to children in resource-constrained settings are many. For anesthesia providers caring for children, the lack of appropriate equipment, inadequate anesthesia workforce and deficiencies in postoperative care are especially difficult. The clinical decisions made by anesthesia providers around when and how to ventilate a child for surgery are influenced by all of these factors and can result in patient management which may vary significantly from that in a high-resource setting. This educational review considers the intraoperative ventilation of a small child in a resource-constrained setting and discusses specific challenges and context-sensitive solutions.

This paper describes the development of a new adaptation of the traditional tracer gas test (TGT) used for total air change rates (ACH) measurement. This adapted TGT, based on constant tracer injec...

Transmission of COVID-19 through close contact and droplets is well established, but the influence of aerosol and surface contamination remains to be determined. Literature is scarce and inconsistent about the viable virus particles free-distance from infected patients, as well as about different swabbing methods for surface contamination evaluation. The aim of this study was to evaluate the most sensitive method for the assessment of surface contamination, classify the likelihood of environmental contamination in risk zones and compare the environmental contamination between oxygenation and ventilatory support.Swabs from potentially contaminated surfaces in a COVID-19 ward, with patients treated with different types of oxygen and ventilatory support, were collected. Three types of swabs were compared in order to evaluate the most sensitive collection method. For risk zone categorization, areas were divided according to the distance from the patient.Of the 63 swabs collected, 17 (27%) tested positive for the presence of SARS-CoV-2. The highest positivity rate was observed with the sterile premoistened swab with saline (n = 8; 38%), but without statistically significant differences. The highest number of positive samples were collected from the high-risk zones, specifically those located one meter from the patient (n = 13; 48%), with statistically significant differences. Only the rooms of patients supported with non-invasive ventilation or high-flow nasal cannula had evidence of bedroom contamination, with 45% and 27% of swab positivity, with statistically significant differences.Our findings favour the premoistened swab without transport medium for surface contamination assessment, even though without statistical differences. A statistically significant trend supporting the division in risk zones, according to the distance from the patient, was also identified. The higher positivity rate from the non-invasive ventilation and high-flow nasal cannula bedrooms suggests a significant association between ventilatory strategies and surface contamination, probably due to higher particle dispersion.Our findings support the use of the sterile premoistened swab without preservation medium, the classification of risk areas considering the distance from the patient, and the variability of RNA dispersion between oxygenation and ventilatory support.Introdução: A transmissão da COVID-19 através do contacto e gotículas está bem estabelecida, mas a importância da sua transmissão através do aerossol e da contaminação das superfícies permanece por determinar. A literatura é escassa e inconsistente em relação à distância mínima livre de partículas víricas, desde um paciente, e também acerca dos mais adequados métodos de colheita de zaragatoas para avaliação da contaminação das superfícies. Os objectivos deste estudo foram avaliar qual o método mais sensível para avaliação da contaminação de superfícies, classificar a contaminação ambiental de acordo com zonas de risco e comparar a contaminação ambiental sob diferentes dispositivos para oxigenoterapia e suporte ventilatório. Material e Métodos: Realizamos colheitas de zaragatoas em superfícies potencialmente contaminadas numa ala COVID-19, onde se encontravam doentes sob diferentes dispositivos para oxigenoterapia e suporte ventilatório. Para avaliar o método de recolha mais sensível para verificação da contaminação das superfícies, comparámos três tipos de zaragatoas. Para a classificação das zonas de risco, dividimos as áreas de acordo com a distância ao doente. Resultados: Das 63 zaragatoas, 17 (27%) testaram positivo para SARS-CoV-2 (27%). A maior positividade foi observada na zaragatoa estéril pré-humedecida com soro fisiológico (n = 8; 38%), mas sem significância estatística. O maior número de amostras positivas obteve-se nas zonas de alto risco, especialmente aquelas a um metro do paciente (n = 13; 48%), com diferenças significativas. Apenas os quartos dos doentes sob ventilação não invasiva e cânula nasal de alto fluxo tiveram evidência de contaminação com 45% e 27% de positividade das zaragatoas, e significância estatística. Discussão: Os nossos resultados favorecem a zaragatoa estéril pré-humedecida sem meio de preservação para avaliação da contaminação das superfícies, embora sem significância estatística. Os resultados suportam também com significância estatística a divisão em zonas de risco de acordo com a distância ao doente. A maior positividade obtida nos quartos dos pacientes que se encontravam a utilizar ventilação não invasiva e cânula nasal de alto fluxo sugere uma associação, com significância, entre as estratégias ventilatória e a contaminação ambiental, provavelmente relacionada com uma maior dispersão das partículas. Conclusão: Os nossos resultados apoiam o uso da zaragatoa estéril pré-humedecida sem meio de preservação, a classificação das áreas de risco considerando a distância ao doente, e a variabilidade da dispersão do RNA entre diferentes dispositivos para oxigenoterapia e ventilação.

Introdução: O presente trabalho estima o risco de infeção por SARS-CoV-2 em ambientes interiores onde a elevada densidade de ocupação resulta numa probabilidade acrescida de contágio, como escolas, escritórios, supermercados, restaurantes e ginásios.Material e Métodos: Foram testadas várias condições nos espaços interiores, tais como a utilização e eficácia de máscaras, a ventilação, a utilização de equipamentos que permitem uma assepsia do ar recorrendo a filtros HEPA, a densidade de ocupação e o tempo de permanência nos espaços, tendo sido utilizado um modelo baseado na dispersão de partículas de aerossóis em espaços fechados e na acumulação e inalação destas partículas ao longo do tempo.Resultados: Os resultados mostraram que a substituição de máscaras sociais por máscaras com classificação FFP2 diminuiu o risco de infeção em 90% nas escolas. Em escolas com ventilação natural, a abertura das janelas na sua totalidade reduziu o risco de infeção em 64% comparativamente com o cenário de janelas fechadas. Nos espaços onde a ventilação mecânica é normalmente utilizada, a probabilidade de infeção reduziu significativamente quando os caudais de ar novo regulamentares foram duplicados (redução de 32% nos escritórios, 42% nos restaurantes, 24% nos supermercados e 46% nos ginásios). A filtragem de ar com filtros HEPA permitiu a redução da probabilidade de infeção em 72% nas escolas, escritórios e restaurantes e 61% nos ginásios. O tempo de permanência nos espaços foi também um fator relevante na variação da probabilidade de infeção, principalmente nas escolas onde se verificou que aulas mais curtas e com um maior número de intervalos reduzem o risco de infeção.Discussão: Os resultados evidenciam a importância de uma adequada ventilação em ambientes fechados, principalmente em locais onde a densidade de ocupação e os tempos de permanência são mais longos, sendo essencial a introdução de ar exterior no interior dos espaços, seja através de meios naturais ou mecânicos. É expectável que os valores de risco de infeção apresentados ao longo do trabalho estejam subvalorizados pelo facto do modelo utilizado apenas considerar a transmissão por partículas inferiores a 10 μm e por, ao assumir o distanciamento social, não incluir a transmissão de curto alcance. A vacinação não foi considerada no modelo pelo facto de ainda não estar disponível quando o trabalho foi realizado.Conclusão: Este estudo vem contribuir para a identificação de medidas que permitem um menor risco de transmissão viral, e consequentemente, uma maior segurança no interior dos espaços fechados.

Refrigerants in vapor-compression systems have a global warming potential thousands of times that of carbon dioxide, yet their spread on the market is unrivalled. Elastocaloric systems, based on solid state cooling, feature among the most promising alternatives. In this paper, an elastocaloric device for air ventilation (ECV) composed by parallel and serial connection of multiple shape memory alloy (SMA) films, is investigated via volume-based finite difference simulation in MATLAB and dynamic building simulation in TRNSYS considering eight cities across the globe. The models assume experimentally demonstrated thermal parameters for the elastocaloric phase transformation around room temperature and a single-storey reference building. The ECV operates according to an optimized, energy-saving logic that includes load partialization and recirculation. Parametric analyses suggest that moderate terminal velocities (∼2 m/s) and a climate-specific design aimed at maximizing the use of the ECV device at nominal cooling capacity are key to reach building cooling needs reductions up to 70% in the considered scenarios. Partialization results in enhanced energy flexibility and conservation, whereas recirculation extends the ECV usability to extreme heat conditions. In absolute terms, the ECV works best under hot climates (e.g. Cairo, Dubai, Brisbane), with monthly cooling load reductions about 2/3-fold compared to cold locations (e.g. Milan, Hobart). The performance is extremely sensitive to the ventilation rate. Thermal zones requiring 1 to 2 air changes per hour are best suited. These findings provide initial insight into design criteria, opportunities and limitations on the use of elastocaloric devices for building ventilation to guide future experimental verification.

Few studies have documented the air quality, noise, thermal comfort, and health risk assessment of household kitchens related to Sub-Sahara Africa. In this paper, air quality (CO and PM2.5), thermal comfort (relative humidity (RH) and temperature), noise, and health risk in urban household kitchens with kerosene-fueled stoves were presented. This study was carried out during the dry season (summer) in the Southwestern part of Nigeria. At the breathing zone, PM2.5 and CO concentrations in the assessed kitchens were measured. In addition, the noise level, RH, and air temperature in the assessed kitchens were also determined. Furthermore, an evaluation of the heat index and health risk of the exposed population to the kerosene-fueled stove kitchens was carried out. During cooking, average CO and PM2.5 concentrations were 24.77 ± 1.05 ppm and 138.10 ± 2.61 µg/m3, respectively, while the RH was 68.34 ± 0.73%, noise level was 51.14 ± 1.08 dB, and temperature was 29.86 ± 0.23 °C. The CO and noise levels were relatively slightly lower and PM2.5 was significantly higher than the thresholds recommended by World Health Organisation. In most of the kitchens, the heat index evaluation revealed the possibility of heat exhaustion, heat cramps, and sunstroke with prolonged exposure of the vulnerable group. The air quality index depicted unhealthy (CO exposure) and very unhealthy (PM2.5 exposure) while the hazard quotient (> 1) implied possible health risk concerning exposure by inhalation. Better design of kitchen with adequate ventilation and improved stoves are suggested.

Spontaneous coal combustion was proved to cause methane accumulation and methane explosions in coal mine goafs. To avoid possible methane explosions, the empirical engineering measure, ventilation dilution, is proposed in coal mines though its disaster prevention mechanism has not been well understood. Through experimental and numerical simulations, the superposition effect of the air leakage and coal combustion-induced chimney effect was studied to reveal disaster prevention effect of ventilation dilution. Research results show that the high temperature area of coal combustion is steady and can provide continuous buoyancy force to form upward airflow even under ventilation dilution; the drifting methane accumulation is observed under the superposition effect of air leakage and upward airflow; ventilation dilution can weaken and even eliminate methane accumulation by overcoming chimney effect, but an increase in coal combustion temperature will enhance the upward airflow of chimney effect to cause methane accumulation again. The competitive relationship between the coal combustion-induced chimney effect and air leakage provides a new insight to study methane migration for the disaster formation and prevention mechanism.

Volume-targeted ventilation (VTV) has been increasingly used in neonatology. In systematic reviews, VTV has been shown to reduce the risk of neonatal morbidities and improve long-term outcomes. It is adaptive ventilation using complex computer algorithms to deliver ventilator inflations with expired tidal volumes close to a target set by clinicians. Significant endotracheal tube leak and patient-ventilator interactions may complicate VTV and make ventilator parameters and waveforms difficult to interpret. In this article, we review the rationale for using VTV and the evidence supporting its use and provide practical advice for clinicians ventilating newborn infants.

Building mechanical ventilation systems are a major driver of indoor air chemistry as their design and operation influences indoor ozone (O3) concentrations, the dilution and transport of indoor-generated volatile organic compounds (VOCs), and indoor environmental conditions. Real-time VOC and O3 measurements were integrated with a building sensing platform to evaluate the influence of mechanical ventilation modes and human occupancy on the dynamics of skin oil ozonolysis products (SOOPs) in an office in a LEED-certified building during the winter. The ventilation system operated under variable recirculation ratios (RRs) from RR = 0 (100% outdoor air) to RR = 1 (100% recirculation air). Time-resolved source rates for 6-methyl-5-hepten-2-one (6-MHO), 4-oxopentanal (4-OPA), and decanal were highly dynamic and changed throughout the day with RR and occupancy. Total SOOP source rates during high-occupancy periods (10:00-18:00) varied from 2500-3000 μg h-1 when RR = 0.1 to 6300-6700 μg h-1 when RR = 1. Source rates for gas-phase reactions, outdoor air, and occupant-associated emissions generally decreased with increasing RR. The recirculation air source rate increased with RR and typically became the dominant source for RR > 0.5. SOOP emissions from surface reservoirs were also a prominent source, contributing 10-50% to total source rates. Elevated per person SOOP emission factors were observed, potentially due to multiple layers of soiled clothing worn during winter.

The proactive control of building’s heating, ventilation, and air conditioning (HVAC) system can reduce energy consumption and provides cost saving. An efficient design of a controller for a complex system such as a building, which is also prone to uncertainties and disturbances, calls for advanced control methods such as model predictive control (MPC). This article presents a tube-based MPC to minimize the net cost of energy usage by the building’s HVAC system while satisfying the comfort level of the building’s occupants. Contrary to the conventional MPC, this controller is robust against model uncertainty and exogenous disturbances affecting the building thermal load model. Compared to other robust approaches such as the min–max controller, the proposed controller is of lower computational complexity and can be used with the environment having complex models, e.g., with nonlinear dynamics. Moreover, the proposed controller shows a satisfactory performance when optimizing an economic objective, such as cost minimization. The merits of using the proposed MPC controller are demonstrated using several simulation cases.

Introduction When a patient suffers an out-of-hospital cardiac arrest, ventilation and chest compressions are often given simultaneously during cardiopulmonary resuscitation. These simultaneous chest compressions may cause a fragmentation of the airflow, which may lead to an ineffective ventilation. This study focusses on the occurrence and quantification of this fragmentation and its effect on ventilation. Materials and methods This study is a single-center observational study, held at Ghent University Hospital. A custom-built bidirectional flow sensor was used to quantify the volumes of ventilation. Adult cardiac arrest patients who were prehospitally intubated and resuscitated by the medical emergency team were eligible for inclusion. Data of the patients who were ventilated and received simultaneous chest compressions, was used to calculate the volumes of ventilation and the amount and volumes of fragmentation. All data in this study is reported as mean (standard deviation; range). Results Data of 10 patients (7 male) with a mean age of 71 years (14;51–87) was used in this study. The mean ventilation frequency was 12/min (2;9–16), the mean minute volume and tidal volume were respectively 6.21 L (1.51;3.79–8.15) and 514 mL (99;422–682). Fragmentation of the airflow was observed in all patients, with an average of 3 (1;2–5) fragments per inspiration and a mean volume of 214 mL (65;112–341) per fragment. Discussion and conclusion Chest compressions during ventilation caused fragmentation of the airflow in all patients. There was wide variation in the number and volume of the fragments between patients. The importance of quantification of airflow volumes and the effect fragmentation of the airflow on the efficacy of ventilation can be essential in improving cardiopulmonary resuscitation techniques and therefore needs further investigation.

Introduction Secondhand cannabis smoke, like secondhand tobacco smoke, creates unhealthy indoor air quality. Ventilation and engineering techniques cannot reduce this pollution to healthy levels, and complete smoke-free policies are the only way to provide healthy indoor environments. Even so, multiple state and local governments have begun to allow indoor smoking of cannabis in businesses. Methods A systematic search of Lexis Advance, NewsBank, and government websites for U.S. state and local laws passed between November 6, 2012 and June 10, 2020 that permit and regulate onsite cannabis consumption businesses was conducted in February–July 2020. Results In total, 6 of 11 states and the District of Columbia that legalized adult-use cannabis as of June 10, 2020 allowed onsite consumption and ≥56 localities within these 6 states allowed onsite cannabis consumption. Only 9% (5/56) of localities ban indoor smoking in these businesses; 23% (13/56) require indoor smoking to occur in physically isolated rooms. Other common local legal requirements address onsite odor control, ventilation/filtration, and building location. Conclusions The majority of the localities that allow onsite cannabis consumption do not explicitly prohibit smoking or vaping inside. Policymakers should be made aware that ventilation and other engineering interventions cannot fully protect workers and patrons. Health authorities and local leaders should educate policymakers on the science of secondhand smoke remediation and advocate for the same standards for secondhand cannabis smoking and vaping that apply to tobacco, particularly because other modes of cannabis administration do not pollute the air.

In modern buildings are also currently used the wooden-based construction systems. A wide range of uses the timber constructions in apartment buildings is a vision of the countries of the EU. The use of timber and the other recyclable materials in apartment buildings creates the precondition for the implementation, operation and disposal of environmental impacts of the EU 2020 Strategy. In the long term is important to transform the construction of buildings to a sustainable standard, which the application of wood in construction supports. Currently, the fire height of timber-based residential construction in most EU countries is limited to 5 storeys, provided that the timber structures are fire-protected. This paper deals with the influence of the ventilation parameter in the time and the intensity of the gas temperature during a fire in a model of an apartment building with a timber load-bearing structure. The load-bearing structure is made of CLT panels, with a mixed structural unit, i.e. with fire-resistant cladding of all load-bearing and fire-dividing structures. FDS (Fire Dynamics Simulator - PyroSim software) is used for dynamic simulations of fire in the model apartment.

In this article, an optimal strategy is proposed for heating, ventilation, and air conditioning (HVAC) systems in commercial buildings to fairly ensure the occupants’ comfort, while participating in frequency regulation. With the nonlinear relationship between temperature setpoint and the fan power, the differences between indoor temperatures and temperature setpoints are considered as the objective to fairly ensure the occupants’ comfort. By the proposed strategy, the task for frequency regulation is optimally distributed according to the capacity of HVAC systems in a load aggregator. Therefore, performing frequency regulation and fairly ensuring occupants’ comfort are achieved simultaneously. Simulations on a two-area interconnected power system show that the proposed optimal strategy can improve the quality of frequency, reduce traditional generator regulation, and ensure the occupants’ comfort fairly.

With the advent of thoracoscopic surgery, the benefits of lung isolation in children have been increasingly recognized. However, because of the small airway dimensions, equipment limitations in size and maneuverability, and limited respiratory reserve, one-lung ventilation in children remains challenging. This article highlights some of the most common error traps in the management of pediatric lung isolation and focuses on practical solutions for their management. The error traps discussed are as follows: (1) the failure to take into consideration relevant aspects of tracheobronchial anatomy when selecting the size of the lung isolation device, (2) failure to execute correct placement of the device chosen for lung isolation, (3) failure to maintain lung isolation related to surgical manipulation and isolation device movement, (4) failure to select appropriate ventilator strategies during one-lung ventilation, and (5) failure to appropriately manage and treat hypoxemia in the setting of one-lung ventilation.

Heat accumulation from wearing personal protective equipment can result in the development of heat-related illnesses. This study aimed to investigate factors of heat stress with and without a US standard issue wildland firefighter helmet. Ten male subjects finished a 90-min exercise protocol in a heat chamber (35°C and 30% relative humidity), with standard issue meta-aramid shirt and pants and a cotton t-shirt, and either with or without a wildland firefighter helmet. A randomised crossover design was implemented, with a minimum 2-week washout period. Heart rate, physiologic strain index, perceived head heat, head heat and skin blood flow of the head and neck were measured. At the conclusion of the 90-min trial, heart rate, physiological strain index, core temperature, rating of perceived exertion and perceived head heat showed a main effect of time (P

The advantages of the demand control ventilation system (DCV) have been widely discussed in previous research studies. However, the literature has not addressed the benefits of DCV on controlling indoor CO2 concentration and minimizing cooling energy consumption for school buildings located in extremely hot climates. Therefore, this paper contributes to the development of DCV and mechanical ventilation systems through a comprehensive evaluation of these systems to maintain acceptable indoor air quality (IAQ) while minimizing cooling energy demands for school buildings located in the harsh hot climate of Saudi Arabia. The evaluation is based on a calibrated whole-building energy model and validated IAQ predictions using field data obtained from a school case study in Jeddah. The results of this research study confirm that hourly and sub-hourly monitoring of indoor CO2 concentration is required to ensure optimal design and operation of the ventilation systems in schools. In addition, the analyses indicate that a 13% increase in cooling energy end-use can result for any additional 0.1 students/m2 density increase in the classrooms. However, the energy penalties related to ventilation needs can be reduced by up to 25% using DCV instead of conventional mechanical ventilation systems for school buildings located in Saudi Arabia’s hot climate.

This research addresses different issues related to the ventilation and the aerosol concentration present in a metal additive manufacturing facility using Laser Powder Bed Fusion (L-PBF) machine. Performing air monitoring requires quantifying the emissions potentially generated in the different areas and during the different L-PBF process phases. A practical Indoor Air Quality (IAQ) assessment protocol is addressed in this research questioning the type of emissions to measure, and the way to collect them. As a measurement strategy for the airborne particles lower than 700 nm, real-time metrology discmini instruments were used (Testo, 1 L.min−1, Forbach, France). The particle number concentration was assessed during three operations: (i) before cleaning the room where the L-PBF machine is located, (ii) during the cleaning phase of the room, and (iii) after the cleaning phase. Without ventilation and without human activity, the background concentration level in the additive manufacturing facility was 5.103 #/cm3 either before or after cleaning. With ventilation and without human activity, the background concentration level was decreased to 4.103 #/cm3 before cleaning, and increased to 1.5.104 #/cm3 after cleaning. Besides, human activity leads to an increase in the number of suspended particles, since they passed from 5.103 #/cm3 to 1.9.104 #/cm3. Finally, a value of 105 #/cm3 was recorded on the operator during the cleaning phase and clearly, show peaks of particle number concentration. It was found that the local ventilation plays a role in the resuspension of particles from surfaces. Indeed, particles deposited on the floor are a source of exposure and hence the need for a clean room. The result section reinforces the necessity of wearing individual protective equipment during the maintenance and cleaning operations of a facility including L-PBF machine.

Ventilation ducts can have a negative effect on the sound reduction index between two rooms if they pass through the dividing structure without treatments. The overall sound reduction of a ventilation duct is dependent on several factors including the transmission loss when sound is breaking in and out from the duct. This study aims to model the sound reduction of a combined system with a separating wall and a ventilation duct through it. Three walls, characterized according to ISO 717-1, are combined with three different ventilation ducts, two circular and one rectangular with different dimensions. Laboratory measurement data are used to determine the sound reduction of the different configurations and the type of treatments needed for each configuration. A proposed model with existing theory for describing sound transmission losses of circular and rectangular ventilation ducts predicts the shape of the measurement data for many frequency bands. A new theory part is developed through an iterative process for circular ducts, which is based on measurements with previous methods and studies as a guide because the existing prediction scheme is somewhat perplexing. For rectangular ducts, the existing theory has been updated to better match measurement data. The application of the proposed theory and model in this article shows similar results when compared to measurements. The difference in weighted sound reduction index between developed theories and measurement data is 0–1 dB for every configuration.