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Dental procedures produce aerosols which may remain suspended and travel significant distances from the source. Dental aerosols and droplets contain oral microbes and there is potential for infectious disease transmission and major disruption to dental services during infectious disease outbreaks. One method to control hazardous aerosols often used in industry is Local Exhaust Ventilation (LEV). The aim of this study was to investigate the effect of LEV on aerosols and droplets produced during dental procedures. Experiments were conducted on dental mannequins in an 825.4 m3 open plan clinic, and a 49.3 m3 single surgery. 10-minute crown preparations were performed with an air-turbine handpiece in the open plan clinic, and 10-minute full mouth ultrasonic scaling in the single surgery. Fluorescein was added to instrument irrigation reservoirs as a tracer. In both settings, Optical Particle Counters (OPCs) were used to measure aerosol particles between 0.3 – 10.0 μm and liquid cyclone air samplers were used to capture aerosolised fluorescein tracer. Additionally, in the open plan setting fluorescein tracer was captured by passive settling onto filter papers in the environment. Tracer was quantified fluorometrically. An LEV device with High Efficiency Particulate Air (HEPA) filtration and a flow rate of 5,000 L/min was used. LEV reduced aerosol production from the air-turbine handpiece by 90% within 0.5 m, and this was 99% for the ultrasonic scaler. OPC particle counts were substantially reduced for both procedures, and air-turbine settled droplet detection reduced by 95% within 0.5 m. The effect of LEV was substantially greater than suction alone for the air-turbine and was similar to the effect of suction for the ultrasonic scaler. LEV reduces aerosol and droplet contamination from dental procedures by at least 90% in the breathing zone of the operator and it is therefore a valuable tool to reduce the dispersion of dental aerosols.

Based on the metro undersea interval from Wawuzhuang Station to Guizhou Road Station of Qingdao Metro Line 1, a physical model system is built for the sake to further study the Ventilation and Smoke Exhaust System (VSES) of this interval tunnel. In the VSES experimental system, it gains data of variable frequencies inputting to fans, consumed-power values of fans, velocities in carriageways and SEDs (Smoke Exhaust Ducts), static pressure in carriageways under the conditions of the TP (Two Pressing-in) and TP+OE (Two Pressing-in + One Extracted-out) combinations of fans. The experimental data are shown that the static pressure field in horizontal carriageways has a symmetrical distribution, whose symmetry axis is as the plane of a smoke ceiling, whether TP or TP+OE. Under the TP+OE, the velocities in SEDs and carriageways are influenced dominantly by an extracted-out fan; two pressing-in fans of the TP combination influence mainly those velocities. A velocity is capable to dilute and coerce a smog flue. The pushing force of the smog flue is supplied by a pressing-in fan with consumed-power values, and another pressing-in fan with the lower values prevents this flue from another carriageway; furthermore, the pulling force of this flue is supplied by an extracted-out fan with the largest consumed-power values. The ratio of the total values of fans to the discharged volume flow rates in both SEDs is proposed as a new criterion, which can quantify VSES performance and is equivalent to airflow pressure; it is shown that the VSES performance of the TP+OE combination promotes gradually and becomes superior to one of the TP. Finally, it is advisory that the TP+OE should be a preferential combination of fans in designs and engineering situ management of extra length and large section tunnel ventilation.

Office occupants spend most of their time in an enclosed indoor environment, controlled by heating, ventilation and air-conditioning (HVAC) systems especially in subtropical regions owing to the hot and humid climate. A reasonable indoor environment evaluation model is necessary to achieve the reliable control of HVAC systems that satisfies the occupants’ health and comfort needs. However, traditional HVAC systems are controlled based on a simple index that does not consider the synthesis of indoor air quality, thermal comfort and occupant preferences. In this paper, we develop a comprehensive evaluation model that encompasses these three aspects based on field survey. Field surveys were conducted to investigate indoor environmental conditions and preferences of the occupants. Collected data were then verified for model hypothesis rationality and reviewed to identify weighting factors using Pearson and regression analysis. Results showed that these parameters had significant correlations without noticeable collinearity and can be integrated using regression method. The weighting factors of each parameter were calculated using occupants’ sensation and expectation to reflect the subjective preferences in model. Finally, an evaluation model expressing the indoor thermal, air quality and occupant preferences was developed to provide an HVAC intelligent control system that is more responsive to occupant needs.

Roadway tunnels often include a reinforced concrete drop ceiling that is hung from the liner to create a plenum that facilitates ventilation and houses utilities. Drop ceiling panels are lightweight compared with the much thicker tunnel liner and can experience significant damage from a fire on the roadway below. This paper examines the flexural response of drop ceiling panels in two representative tunnels to standard fire curves as well as several realistic fires due to vehicular accidents. Standard fire demands as per the Rijkswaterstaat and ASTM E1529 fire curves are uniformly applied to the ceiling panels, and heat exposure contours for typical vehicle fires with heat release rates of 30, 100, and 200 MW are generated from the software CFAST. The finite element analysis software SAFIR is used to evaluate the thermo-mechanical behavior of the ceiling panels when subjected to various thermal demands from the fire below. The analysis results indicate that drop ceiling panels are highly vulnerable to fire-induced damage and potential collapse both during a fire’s active heating phase (from simultaneous loss of capacity and restraint of thermal expansion) and during the subsequent cooling period (from tension that develops when the permanently deformed panel thermally retracts). The potential for fire-induced damage or collapse of the drop ceiling panels can be mitigated by reducing the fire hazard, removing the drop ceiling, or enhancing the fire resistance of the panels via the application of passive protection or structural hardening.

In factories where high-risk chemical pollutants are treated, it is essential to anticipate response measures in the event of chemical pollutant leakage to minimize adverse health effects on workers. When high-risk liquid chemical pollutants are assumed to be leaked inside enclosed spaces, it becomes crucial to predict the non-uniform concentration distributions in enclosed spaces and evaluate the health impacts and risks of short-time exposure to prevent large-scale accidents. Therefore, we have developed an emergency ventilation system for controlling the inhaled contaminant dose of factory workers. In this study, assuming a worst-case scenario liquid chemical pollutant leak in an enclosed factory space, the advantages and performance of a hybrid ventilation system that combines displacement and push–pull type ventilation systems were numerically investigated. Installation of wall materials that facilitate photocatalytic oxidation (PCO) reactions for background passive concentration control was also discussed. Based on the demonstrative numerical analyses for a realistic factory space, push–pull type ventilation system was confirmed to effectively suppress chemical pollutant diffusion in enclosed spaces with a low ventilation rate. Wall materials with the PCO mechanism had a certain contribution to the control of peak concentration.

In the first months of the COVID-19 pandemic in Europe, many patients were treated in hospitals using mechanical ventilation. However, due to a shortage of ICU ventilators, hospitals worldwide needed to deploy anesthesia machines for ICU ventilation (which is off-label use). A joint guidance was written to apply anesthesia machines for long-term ventilation. The goal of this research is to retrospectively evaluate the differences in measurable ventilation parameters between the ICU ventilator and the anesthesia machine as used for COVID-19 patients. In this study, we included 32 patients treated in March and April 2020, who had more than 3 days of mechanical ventilation, either in the regular ICU with ICU ventilators (Hamilton S1), or in the temporary emergency ICU with anesthetic ventilators (Aisys, GE). The data acquired during regular clinical treatment was collected from the Patient Data Management Systems. Available ventilation parameters (pressures and volumes: PEEP, Ppeak, Pinsp, Vtidal), monitored parameters EtCO2, SpO2, derived compliance C, and resistance R were processed and analyzed. A sub-analysis was performed to compare closed-loop ventilation (INTELLiVENT-ASV) to other ventilation modes. The results showed no major differences in the compared parameters, except for Pinsp. PEEP was reduced over time in the with Hamilton treated patients. This is most likely attributed to changing clinical protocol as more clinical experience and literature became available. A comparison of compliance between the 2 ventilators could not be made due to variances in the measurement of compliance. Closed loop ventilation could be used in 79% of the time, resulting in more stable EtCO2. From the analysis it can be concluded that the off-label usage of the anesthetic ventilator in our hospital did not result in differences in ventilation parameters compared to the ICU treatment in the first 4 days of ventilation.

Occupancy behaviour in buildings can impact the energy performance and the operation of heating, ventilation and air-conditioning systems. To ensure building operations become optimised, it is vital to develop solutions that can monitor the utilisation of indoor spaces and provide occupants’ actual thermal comfort requirements. This study presents the analysis of the application of a vision-based deep learning approach for human activity detection and recognition in buildings. A convolutional neural network was employed to enable the detection and classification of occupancy activities. The model was deployed to a camera that enabled real-time detections, giving an average detection accuracy of 98.65%. Data on the number of occupants performing each of the selected activities were collected, and deep learning–influenced profile was generated. Building energy simulation and various scenario-based cases were used to assess the impact of such an approach on the building energy demand and provide insights into how the proposed detection method can enable heating, ventilation and air-conditioning systems to respond to occupancy’s dynamic changes. Results indicated that the deep learning approach could reduce the over- or under-estimation of occupancy heat gains. It is envisioned that the approach can be coupled with heating, ventilation and air-conditioning controls to adjust the setpoint based on the building space’s actual requirements, which could provide more comfortable environments and minimise unnecessary building energy loads. Practical application Occupancy behaviour has been identified as an important issue impacting the energy demand of building and heating, ventilation and air-conditioning systems. This study proposes a vision-based deep learning approach to capture, detect and recognise in real-time the occupancy patterns and activities within an office space environment. Initial building energy simulation analysis of the application of such an approach within buildings was performed. The proposed approach is envisioned to enable heating, ventilation and air-conditioning systems to adapt and make a timely response based on occupancy’s dynamic changes. The results presented here show the practicality of such an approach that could be integrated with heating, ventilation and air-conditioning systems for various building spaces and environments.

Damaging factors such as airborne microorganisms, relative humidity, ventilation, temperature and air pollutants are the major concerns of the tropical climate of Kolkata, India where our study site, 172-year-old St. Paul’s Cathedral is located. In this context, the aim was to develop an equation to assess the management priority and which factors would be more responsible for potentially damaging the heritage building. The temperature varied from 28°C to 31°C, relative humidity was recorded 72% over a period of 14 days in the prayer hall whereas almost constant temperature (27°C) and relative humidity (55%) were recorded in crypt. Air movement was recorded 0.5–3 m s−1 in both crypt and prayer hall. Sulphur dioxide and oxide of nitrogen concentration were lower than the standard mentioned by the Central Pollution Control Board, India. The fungal load was lower inside the crypt (237 CFU m−3) than in the prayer hall (793 CFU m−3). Calculated potential damage for prayer hall and crypt was found to be 48.75% and 37.08%, respectively. Results revealed that microbial load and relative humidity were the potent factors for damage to the building. Continuous air movement, that is, ventilation and building design here played significant roles. The Heritage Conservation Committee can use the data for better management.

This study investigated effects of incident wind angles on wind velocity distributions in wakes of two generic building configurations, namely, ‘T’- and ‘+’-shaped, and the air pressure distributions along their leeward walls by using computational fluid dynamics simulations. Results show that when the wind approaches laterally (90°) (vs. when the wind is direct (0°)), the downwind length and maximum bilateral width of the low-wind velocity zone in the wake of ‘T’-shaped building decrease by 11.5% and 37.9%, respectively. When the incident wind is oblique (45°) (vs. when it is direct), the length and width of this low-wind velocity zone in the wake of ‘+’-shaped building decrease by 15.0% and 30.9%, respectively. Furthermore, results show that the air pressure on the leeward walls of the ‘T’- and ‘+’-shaped buildings gradually decreases along with the building height. The resulting low-wind conditions on upper floors of buildings reduce the fresh air intake of their leeward units utilizing natural ventilation. It is particularly apparent in the case of direct approaching wind. Thus, the appropriate selection of building configurations and their orientations allows for the most effective use of wind to enhance ventilation in indoor and urban environments.

The indoor air quality (IAQ) of five low-energy London apartments has been assessed through the measurement of 16 key pollutants, using continuous and diffusive methods across heating and non-heating seasons. This case study approach aimed to assess the presence of pollutants within low-energy apartments and to better understand the role of ventilation and seasonal variations in indoor air quality. The results indicate strong seasonal variations, driven by increased natural ventilation rates over the summer monitoring period. A combined metric for indoor and outdoor pollutants ( Itot) suggests that the IAQ in the winter ( Itot = 17.7) is more than twice as bad as that seen in the summer ( Itot = 8.6). Formaldehyde concentrations were lower in the non-heating season, indicating increased ventilation rates more than offset increased off-gassing, in contrast to findings in other studies. However, increased summertime ventilation rates were observed to increase the proportion of outdoor pollutants entering the internal environment. This resulted in higher indoor concentrations of NO2 in the summer than the winter, despite significant reductions in outdoor concentrations. These results demonstrate the impact of ventilation practices upon IAQ, the influence of occupant actions and the complex relationship ventilation rates play in balancing indoor and outdoor sources of air pollution.

Occupant health can be strongly influenced by indoor air quality due to time spent indoors (90%). Such quality can be impacted by indoor atmospheric pollutants present. Therefore, demand-controlled ventilation can be a key to improving indoor air quality. The main aim herein is to scrutinize measurement results of several air pollutants possibly existing inside university building including CO2, volatile organic compounds, formaldehyde, benzene, CO, PM2.5 during three measurement campaigns (March 2017, May 2017 and October–November 2017) via a smart sensor specially developed. Likewise, some factors to assess comfort such as relative humidity and ambient air temperature were examined. CO2 were found to be higher during periods of occupancy with concentrations exceeding 2000 ppm during the first campaign. As a result, the occupants felt uncomfortable. Analysis of the survey results regarding the indoor air temperature showed that 80% of occupants found the temperature during school periods to be uncomfortable. In addition, the ICONE air containment index was extremely high, indicating that the deemed class was confined during occupancy. The outcomes will be useful for the development of future indoor air quality guidelines, ventilation design and occupant satisfaction in buildings.

A closed suction system is used to remove endotracheal secretions without interrupting the patient’s ventilation. Closed suctioning may reduce adverse effects associated with suctioning with, for example, decreased clinical signs of hypoxemia and limited environmental, personnel, and patient contamination. However, it is not clear whether ventilation is maintained during the procedure. We aimed to determine the effects of endotracheal tube (ETT) size, suction catheter (SC) size, and SC length in the ETT on ventilation parameters measured during suction. Suction was performed on a test lung, ventilated with either volume-controlled continuous mandatory ventilation (VC-CMV) or pressure-controlled continuous mandatory ventilation (PC-CMV) using ETT sizes of 6.0–8.5 mm paired with SC sizes of 8–16 French gauge (Fr = 0.33 mm). Airway resistance ( Raw), peak inspiratory pressure (PIP), positive end-expiratory pressure (PEEP), and expiratory minute volume ( Vexp) were recorded for each ventilation episode by a HAMILTON-G5 ventilator. Here, Raw was considerably increased by insertion of the SC into the ETT. This Raw effect altered the PIP and Vexp. PIP was increased in VC-CMV because the ventilation area of the ETT was reduced, and Vexp was decreased in PC-CMV in relation to the size of the SC. PEEP decreased with application of the 16 Fr SC and 30 L/min flow rate in VC-CMV. We conclude that airway pressure and minute volume are not maintained during closed endotracheal suctioning with VC-CMV and PC-CMV, respectively. The degree of interference to ventilation is affected through selection of appropriate SC size and ventilation settings.

The objective of this research was to determine the effect of multiple layers of materials typical of those used in air pneumatic compression devices (which require air impermeable layers to function) on thermal and water vapor resistance. The experimental set-up included: (a) single layers of two next-to-skin knit fabrics in both relaxed and extended conditions, (b) two layers of silicone, and (c) a multi-layered assembly comprised of a next-to-skin fabric and two layers of silicone. Structural properties (thickness, mass) dominated thermal resistance of the multi-layered assembly, and the silicone layers rendered this assembly impermeable to water vapor as expected. Results confirmed the need for some form of 'ventilation' to facilitate water vapor transfer from a potential user’s skin to the environment. By creating 18 circular vents across the silicone layers (each vent 314 mm2), which formed ventilation of ∼2% of total surface area, the water vapor resistance of the multi-layered assembly dropped significantly from very high (but non-measurable) to below ∼300 m2Pa/W, although ventilation did not improve the thermal resistance of the multi-layer arrangements. Results of this research will enable manufacturers of pneumatic compression devices to develop devices comprised of a multiple layer arrangements i.e. a knit fabric next-to-skin layer and silicone layers with optimized vents across the silicone layers, so that the user can continue the compression treatment with an acceptable microenvironment.

The article presents experimental studies of typical Finnish highly insulated (HI) envelopes with thermal resistance values ( R value) for the wall and roof inside the ventilation cavity between 7.7 and 8.1 m2K/W and 13 m2K/W, respectively. The conditions in the ventilation cavities were studied by using typical and increased R values for the exterior part of the cavity, which were 0.18 m2K/W and 1.57 m2K/W in the walls, and 0.13 m2K/W and 2.13 m2K/W for the roof. With higher exterior R values of 1.57 m2K/W and 2.13 m2K/W, the cavity temperature increased only after closing the inlet gap of the cavities. If the cavity inlet was closed, the restriction of the outlet gap from 20–25 mm to 10 mm had no significant effect on the temperatures. A closed ventilation inlet resulted in increased absolute humidity in the cavity, which indicates that the restriction of cavity ventilation should be made with care to avoid impairing the drying-out ability. The computational analysis showed that the optimal air change rates in the wall and roof cavities of HI structures were 4–40 1/h and 20 1/h, respectively. The conventional 22-mm-thick wood cladding enables safe cavity conditions in HI walls if the vapor barrier is vapor tight and other moisture sources are low. A lower heat flux and additional heat loss caused by cloudless sky at night support the observation that HI roofs have a higher moisture risk. In HI roofs, a conventional exterior R value of 0.13 m2K/W should at least be increased to the range of 0.3–0.4 m2K/W, which is achieved, for example, by a 20-mm-thick mineral wool board under the roofing. The use of mold-resistant materials in the ventilation cavity is recommended to mitigate the possible ramifications of the moisture behavior of HI roofs.

In this study, adaptive branch fan performance in a distributed fan ventilation system was tested. The results demonstrate that the adaptive branch fan stabilises the branch air flow rate within a certain air pressure range corresponding to the branch duct inlet, and this range becomes increasingly narrow as the fan control signal is adjusted to reduce the speed of the fan. The adaptive branch fan is less affected by the main fan and other branch fans in the distributed fan ventilation system because it has a good self-adaptive ability of ventilation duct resistance characteristics and anti-interference ability of the air flow rate. Furthermore, the hydraulic characteristics of the branch fans in the distributed fan ventilation system were analysed. The new performance characterisation parameters and method for modifying the engineering design for the adaptive branch fan were presented. Practical application: This study investigates the adaptive performance of the branch fan in a distributed fan ventilation system. Our results demonstrate that the new branch fan can stabilise the air flow rate in a mechanical ventilation system. More importantly, we not only propose performance characterisation parameters of the adaptive branch fan that are important for understanding the operation of a mechanical ventilation system, but also present a method of engineering design application. This study can guide the design and operation of mechanical ventilation systems.

The impact of human body heat dissipation on the containment of a fume hood was conducted via experiments and numerical model. The experiments evaluated hood face velocity and the temperature around the mannequin; the results validated the simulation. The numerical model was based on the governing equations of fluid flow via the finite volume method. The face velocities (0.3–0.9 m·s− 1 ) and temperature differences (11°C, 8°C and 5°C) between the surface of the mannequin and its surroundings were used as variables. The numerical results show that in addition to the blockage effect of the worker standing in front of the fume hood, there is a more important thermal effect on the containment of fume hood. The thermal plume carries pollutants leaking out of the hood face to the breathing zone. The face velocity and dimensionless value (Gr/Re 2 ) are recommended to be 0.4–0.6 m·s− 1 and 20–35 respectively, to reduce the influence of human thermal plume on the containment of fume hood and energy waste. The formula related to the rising distance of thermal plume, Grashof and Reynolds numbers (Gr/Re 2 ) was determined.

The outbreak of pneumonia caused by 2019 Novel Coronavirus arises significant concern for virus transmission and control. The control of the indoor environment or public-enclosed environment is crucial to reduce the risk of infection. Heating, ventilation, air-conditioning (HVAC) systems are used to create a healthy, thermal-comfort indoor environments. Thus, the rational use of HVAC systems is of great importance for the environmental control to reduce infection risk and to improve human wellbeing in the pandemic. In order to satisfy the requirement of better healthy environment and more thermal comfort performance of indoor ventilation system, prevention of indoor pollution is essential, especially considering the purpose of disease transmission resistance. This paper investigated the collective contagion events in enclosed spaces as well as engineering control against virus spread with ventilation systems for health-care facilities and public vehicles. Future challenges of HVAC design and control were discussed.

In Portugal, residential buildings commonly have their ventilation strategy changed after commissioning. This occurs due to the building managers' willingness to reduce shared costs with the electricity needed for fan operation. However, this option is not technically supported, and the effects of such a strategy on indoor air quality-related to human pollutants are yet to be quantified. CO2 was monitored in 15 bedrooms and air exchange rates were calculated for each room. The air exchange rate values ranged from 0.18 to 0.53 h−1 when mechanical extraction ventilation was off, and from 0.45 to 0.90 h−1 when mechanical extraction ventilation was on, which represents an average increase of 119%. With the current intermittent ventilation strategy, all rooms remain above 1500 ppm for a given percentage of time, and 12 rooms presenting CO2 concentrations above 2000 ppm. Simulations of theoretical CO2 concentrations, for a non-interrupted mechanical ventilation strategy show that no rooms would accumulate CO2 concentrations above 2000 ppm, and only 25% would present CO2 concentrations above 1500 ppm. Pearson correlations between the monitored CO2 and human and spatial factors identified two relevant parameters. Those parameters correspond to ratios between CO2 generation and floor area ([Formula: see text]), and airflow with CO2 generation ([Formula: see text]). The proposed ratios could be used as ways to optimise ventilation costs and indoor air quality.

Computational fluid dynamics have been used to numerically study the particle diffusion and deposition in a residential kitchen under several ventilation modes. First, combining the renormalized group turbulent model with cooking release conditions, the airflow field in a kitchen was simulated and its airflow characteristics were analysed. Second, the drift flux model was adopted to predict the spatial distribution of particles, quantifying various mechanisms that affect the particle diffusion. Finally, the deposition flux towards the wall was determined by a semi-empirical particle deposition model. The results show that the rising thermal plume has a great influence on the diffusion of particles. When particles with small sizes diffuse in the kitchen, the influence of turbulence plays a crucial role. The case studies show that the ventilation form is an important factor affecting the concentration distribution and deposition of particles. However, the ultrafine particles distribution with different sizes is little sensitized to changes of the airflow field. The results also show that the main determinant of the deposition flux is the particle concentration near the wall. There is not much difference in the particle deposition flux under different particle sizes, which is related to the larger air exchange rate.

Background: CPR model of a resuscitation to be ventilated with a bag valve mask constitutes a discussion when evaluated with the current guidance. Objective: This study aims to compare the synchronous (30–2) ventilation–compression method with asynchronous 110/min compression–10/min ventilation in cardiac arrests where an advanced airway management is not applied and where ventilation is provided by a bag valve mask on a mannequin. Methods: This simulation trial was performed using two clinical cardiopulmonary resuscitation scenarios: an asynchronous scenario with 10 ventilations per minute asynchronously when compression is applied as 110 compression per minute and a synchronous scenario in which 30 compressions:2 ventilations were performed synchronously. A total of 100 people in 50 groups applied these two scenarios on mannequin. Ventilation and compression data of both scenarios were recorded. Results: Evaluating the compression criteria in both the scenarios performed by 50 groups in total, in terms of all criteria except compression fraction, there was no statistically difference between the two scenarios (p > 0.05). Compression fraction values in the asynchronous scenario were found to be statistically significantly higher than the synchronous scenario (96.02 ± 2.35, 81.34 ± 4.42, p Conclusion: In our study, we concluded that the cardiopulmonary resuscitation applied by the synchronous method reached better ventilation volumes. Evaluating together with any interruption in compression, comprehensive studies are needed to reveal which patients would benefit from this result.

Coronavirus disease 2019, otherwise referred to as COVID-19, started in China and quickly became a worldwide pandemic. Beginning in March 2020, nonessential businesses in the United States were closed, and many communities were under shelter-in-place orders. As of May 2020, some business sectors started reopening, even amidst concerns of worker health as the pandemic continued. In addition to physical distancing, cleaning and disinfection routines, and using face coverings, building ventilation can also be an important risk mitigation measure for controlling exposure to SARS-CoV-2 indoors. A number of studies to date, however, have focused on ventilation in medical facilities (e.g. hospitals) as the risk of transmission of SARS-CoV-2 is higher there (because of the close proximity of workers to patients who have the disease and their treatment procedures). Few studies have focused on ventilation use in nonmedical settings (e.g. office buildings and school classrooms), despite the large population of workers and community members in these facilities. In this article, we review the role that building ventilation can play in minimizing the risk of SARS-CoV-2 transmission in nonmedical environments and some recommended protocols to follow for its proper use, including cleaning and maintaining mechanical ventilation systems for businesses, schools, and homes.

Several studies based on in vivo or in vitro models have found promising results for the noble gas argon in neuroprotection against ischaemic pathologies. The development of argon as a medicinal product includes the requirement for toxicity testing through non-clinical studies. The long exposure period of animals (rats) during several days results in technical and logistic challenges related to the gas administration. In particular, a minimum of 10 air changes per hour (ACH) to maintain animal welfare results in extremely large volumes of experimental gas required if the gas is not recirculated. The difficulty with handling the many cylinders prompted the development of such a recirculation-based design. To distribute the recirculating gas to individually ventilated cages and monitor them properly was deemed more difficult than constructing a single large enclosure that will hold several open cages. To address these concerns, a computational fluid dynamics (CFD) analysis of the preliminary design was performed. A purpose-made exposure chamber was designed based on the CFD simulations. Comparisons of the simulation results to measurements of gas concentration at two cage positions while filling show that the CFD results compare well to these limited experiments. Thus, we believe that the CFD results are representative of the gas distribution throughout the enclosure. The CFD shows that the design provides better gas distribution (i.e. a higher effective air change rate) than predicted by 10 ACH.

Impacts of the laminar airflow ventilation system design factors on contaminant removal and thermal comfort condition in an operating room have been investigated by means of Lagrangian-based particle transport using the non-Boussinesq modeling of the buoyancy effects. An operating room including staffs and a patient with realistic human geometries and two surgery lights are included in simulations. The laminar airflow system is placed on the ceiling with a surrounding fixed-height partial wall and the air barrier supply grills. Effects of density change in mixed convection flow regime are included by the non-Boussinesq modeling of the exact air density variation. The predicted mean vote, the age of air, the colony-forming units per cubic meter, the average temperature, the average velocity, the relative humidity, the density distribution, and the positions of particles are calculated to assess the indoor air ventilation quality. A total of 27 simulation cases have been considered to determine the impact of three main design factors including the laminar airflow system area, the supply air, and the air barrier velocities on the performance of the system. It is concluded that for the curtain velocity of 2 m/s, the thermal comfort reduces with increasing the laminar airflow velocity, but for the third staff, the results show that for small laminar airflow areas, the speed of the inlet port should be reduced and for the larger sizes, the inverse of this trend is recommended. Moreover, for all cases the humidity varies within the range of 55%–56%, which agrees well with the suggested standard humidity range between 50% and 60%. It is concluded that the cases of the laminar airflow velocity equal to 0.3 and 0.5 at the curtain velocity of 1 m/s are generally more appropriate than other cases due to less accommodation of particles near the entire body of the patient.

The aerosolized dust produced during coal mining operations pollutes underground air environment and increases the risk of lung diseases in coal miners, such as pneumoconiosis. Aiming to solve the dust pollution in mechanized excavation face, the integrated vortex ventilation and dust removal system is designed based on swirling jet flow theory. The design principles and technological parameters of the major components of integrated vortex ventilation and dust removal (IVVDR) system, namely vortex ventilation device and wet dust collector are described systematically. Through numerical simulation and field experiments, the dust control and dust removal effects of IVVDR system were analyzed and tested. The numerical simulation results show that the swirling jet flows produced by wall-attached duct can control most of total and respirable dust in the area between working face and exhausting air outlet. In addition, the IVVDR system provides better control and removal effect of smaller respirable dust. In field application, the IVVDR system has better performance compared with the long-compression short-suction (LCSS) ventilation. In conclusion, the concentration of total and respirable dust in purified air are below 10 mg/m3, and in accordance with the mine safety regulations.

In this article, a comparative study on the outdoor air pollutant prevention and indoor thermal comfort for different types of ventilation was carried out. Both objective experiment, subjective experiment and computational fluid dynamics (CFD) simulation were conducted to investigate the differences in air pollutant prevention and thermal comfort between four common ventilation methods, namely supplying on the ceiling and returning on the ceiling (SC-RC), supplying on the ceiling and returning on the side wall (SC-RSW), supplying on the side wall and returning on the ceiling (SSW-RC), and supplying on the side wall and returning on the side wall (SSW-RSW). Results show that SSW-RSW can provide the highest indoor air quality according to the indoor average PM2.5 concentration. Overall thermal sensation was introduced to evaluate the indoor comfort under the four ventilation methods. The voting results show that the indoor thermal comfort can be enhanced by 29–36% under SSW-RSW and SSW-RC. Therefore, SSW-RSW is more suitable for providing a healthy and comfortable indoor environment.

Background: The food truck industry has rapidly expanded in the United States and kitchen environments can contain harmful contaminants from cooking emissions. The objective of this study was to examine the levels of aldehydes, polycyclic aromatic hydrocarbons (PAHs), and Particulate Matter (PM)2.5 generated from cooking process in food trucks. Methods: Area sampling was performed twice at two participating food trucks during work shifts. Nine aldehydes and eighteeen PAHs were analyzed according to the relevant standard methods while PM2.5 was measured with a real time monitor. Ventilation performance of the food truck exhaust hoods was also investigated using a thermal anemometer. Findings: Formaldehyde was the only aldehyde detected in all samples with a concentration range of 7.16 to 53.68 µg/m3. No PAHs were detected above the limit of quantification. Average PM2.5 concentrations ranged from 0.65 to 7.03 mg/m3. Food Trucks 1 and 2 have an average exhaust flow rate of 211 and 215 L/s per linear meter of hood, respectively. Conclusions/Application to practice: Overall, Food Truck 2 had consistently higher levels of aldehydes and PM2.5 with comparable ventilation performance as Food Truck 1. The higher exposure levels of Food Truck 2 could possibly be attributed to a larger volume of food orders and the heavy duty cooking equipment with an exhaust flow rate below the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) recommendations. Although more investigations need to be performed, the findings could be used to raise awareness of food truck workers and health practitioners to reduce potential exposure risks.

Air filters play an important role in a heating, ventilation and air-conditioning (HVAC) system to maintain good indoor air quality of a building. The air filter test standards act as a guideline to evaluate the air filter performance. The current global test standard, ISO 16890:2016 adopts particulate matter classification which can be easily understood. The European standard, EN 779:2012 is obsolete and replaced by ISO 16890:2016 in June 2018. ASHRAE 52.2:2017 which adopts the minimum efficiency reporting value (MERV) classification is still widely used in the United States. Some countries in Southeast Asia such as Malaysia, Brunei and Singapore are applying different standards: EN779, ASHRAE 52.2 and ISO 16890. A standardization of the air filter testing and classification is undoubtedly important in the global air filtration market. This paper can act as a reference and assist these developing countries in adopting the suitable air filter testing standard to develop their national standard. As all three standards have no specifications on energy efficiency classification, the energy rating system can be obtained using Eurovent 4/21-2018. The HVAC-system-supplied air quality can be further improved with the consideration of WHO annual mean pollutant limits and EN 16798-3 air classification to determine the supply air cleanliness. Practical application: Although EN 779 is replaced by ISO 16890, some developing countries are still in the transition period. Manufacturers and consumers apply different standards which are EN 779, ASHRAE 52.2 and ISO 16890; therefore, a global filter testing standardization is important. This paper can act as a reference and assist the countries in other regions especially in Southeast Asia to develop respective national standard. Besides, some recommendations are given to improve the air filtration and ventilation system by referring to the WHO guidelines for the air pollutant limits, EN 16798-3 for the supply air quality and Eurovent 4/21 for the air filter energy rating.

Objectives: To discuss the indication for performing a mastoidectomy with catheter placement in patients with chronic tympanostomy tube otorrhea. Methods: The Medical Literature Analysis and Retrieval System Online was searched via PubMed for relevant articles using serous mastoiditis, mastoidectomy, chronic otorrhea, tube otorrhea, tympanostomy tubes, and biofilm as keywords. Results: Further understanding of the pathophysiology of otorrhea and the development of ototopical fluoroquinolones have made a draining tympanostomy tube more manageable. Nevertheless, chronic otorrhea refractory to an otolaryngologist’s traditional treatment algorithm still occurs and may benefit from a mastoidectomy with antibiotic irrigation using a catheter in certain cases. We theorize that resolution of otorrhea results from this technique by decreasing the burden of diseased mucosa and providing a larger concentration or dose of antibiotic to the middle ear cleft through the antrum. High-resolution images of the technique and catheter placement are included in this review. Conclusions: Despite being an uncommon management strategy, the literature suggests an indication for performing a mastoidectomy in a small percentage of patients with a chronically draining tympanostomy tube.

Experiments and theoretical analyses are conducted in a residential building in Changzhou to study indoor PM2.5 concentrations by establishing a combined parameter model. An alternative method for predicting the particle deposition rate and penetration coefficient is proposed, and its accuracy is tested and verified by experiments using time-dependent concentrations and air exchange rate measurements. The predicted PM2.5 penetration coefficient increased from 0.70 to 0.88 when the air exchange rates were varied from 0.2 h−1 to 0.5 h−1. In addition, outdoor sources of PM2.5 dominantly contributed approximately 90% to 98% to the indoor concentrations for both mechanically and naturally ventilated structures. Finally, a mathematical model for predicting the indoor concentration is presented using a mass balance equation, which estimates the parameter values in the building. The indoor PM2.5 concentrations ranged from 40 to 46 µg/m3 by using a fresh air system with 82% filtration efficiency, while those by using open windows for natural ventilation ranged from 105 to 118 µg/m3 when the outdoor PM2.5 concentration ranged from 115 to 137 µg/m3. The results of this study can be used to estimate the indoor particle level. Practical application: By applying the ventilation criteria for acceptable indoor air quality in ASHRAE Standard 62.1, the indoor PM2.5 monitoring results show serious pollution in dwellings in 2018. More dwellings are expected to maintain a clean indoor environment in the future. Thus, it is crucial to consider the indoor PM2.5 pollution risk in the building design to prevent the possible consequences of unsafe high indoor concentrations. The use of this prediction model, as discussed in this article, will provide further information on the influence of the particle deposition rate ( K) and penetration coefficient ( P) on indoor PM2.5 concentrations.

Radon is a radioactive pollutant that could pose hazards to the surrounding environment and people due to its radioactive decay progenies. In this study, numerical simulations of radon dispersion were conducted under natural and mechanical ventilation with an air-purifier for radon. Factors such as the air supply speed, position and air supply angles of the purifier were considered. Results showed that the increase in the air supply speed from the purifier was an effective solution to reduce indoor radon pollution. The effect was better when the purifier was in the middle of the room. The purification effect was similar when the air supply changed under natural ventilation, while purification function was more effective when the air supply angle was 60° under the mechanical ventilation condition. An effective dose estimation involving typical ventilation schemes with radon purifier was evaluated. Using this approach, the radiation effect on occupants was computed. The calculated effective dose was 0.9 mSv y−1 when the air supply speed of the purifier was 0.2 m s−1 under natural ventilation. As a result, the effective dose calculated was under the annual effective dose limit of 3–10 mSv y−1 recommended by the International Commission on Radiological Protection (ICRP) for public exposure.

Objective:To study the hypothesis that children scheduled for ventilation tube insertion (VTI), a surrogate procedure reflecting otitis media (OM) presence, are overweight or obese.Patients and Methods:Charts of Israeli children aged 0 to 9 years undergoing VTI with or without adenoidectomy between 9/1/17 and 3/31/19 in a secondary level hospital were retrospectively identified. We compared their mean body mass index (BMI, kg/m2) to the mean BMI of a control group comprised of children who underwent surgeries unrelated to OM (fracture fixation/reduction, inguinal/umbilical hernia repair, meatotomy, appendectomy). BMI measurements were plotted on gender- and age-matched curves to determine BMI percentile, and were also compared to the national pediatric overweight/obesity data. Normal weight was defined as BMI percentile 97%.Results:The VTI group included 83 children (mean age: 3.5 ± 1.8 years). The control group included 77 children (mean age: 6.3 ± 1.9 years). No statistically significant difference was found in the mean BMI values between both groups ( P = .22). When compared to age- and gender-adjusted 50th BMI percentile of the general pediatric population, the mean BMI of the VTI group was significantly higher: for boys, 16.9 versus 15.2 ( P Conclusion:Children undergoing VTI were overweight when compared to their age- and gender-matched peers. This observation was more noticeable in boys.

Airflow patterns are essential for heating, ventilation and air conditioning (HVAC) systems. Traditional HVAC systems are predesigned and operated using a fixed airflow pattern. However, the indoor occupancy and heat source always vary and therefore, the fixed flow pattern cannot efficiently maintain the required indoor environment conditions. In this study, a novel Adjustable Fan Network (AFN) for improving airflow pattern manoeuvrability is proposed. It integrates multiple small and adjustable axial fans into an AFN, enabling it to change the airflow pattern based on the actual demand with only one set of equipment. Further, the outflow characteristics of two types of axial fans were measured using a quad-view colour sequence particle streak velocimetry (CSPSV) in a test chamber. The ventilation system was then designed based on typical scenarios. Finally, the performance of the AFN was evaluated under different scenarios using a quad-view CSPSV. Based on the results, it was evident that the AFN can provide a better direct supply of air to the occupied zone under different scenarios. With the growing demand for personal thermal comfort and energy-saving in HVAC systems, the novel AFN system has a great potential to be a highly controllable terminal for demand-oriented ventilation.

Operating rooms (ORs) often have door openings connected to uncontrolled areas that are more contaminated. Opening the door may allow an inflow of contaminated air, degrade the microbiological air cleanliness and possibly cause surgical site infections (SSIs). This study numerically investigated the transient airflow and bacteria-carrying particles spread caused by the opening of a sliding door in an OR with mixing ventilation. Results showed that a single door opening raises the overall OR contamination by 2.1 colony-forming units per cubic metre (CFU/m3) under a temperature difference of about 3°C. With a similar level of overall contamination, the risk of infections differs dramatically, as the corresponding contamination at the surgical site ranges from lower than 1 CFU/m3 to higher than 10 CFU/m3. This implies that quantifying only the air volume exchange is not sufficient for a valid and reliable assessment of the impact of door openings on the risk of SSIs. Temporarily reducing the OR exhaust flow during door operation was found to be an effective solution to minimize the impact of door openings on the risk of infections. In the case examined in the present study, a 20–30% reduction in OR exhaust flow decreases the airborne contamination to a sufficiently low level.

Lateral exhaust systems have commonly been applied to capture polluted buoyant jets in many industrial processes, such as casting and metallurgy. Compared with the normal conditions of design manuals, the capture efficiency of a lateral exhaust hood (LEH) is often weakened by two factors in actual processes: the unsteady buoyant jet released from the operating surface, and the plume formed above a high-temperature workpiece placed between the LEH and the operating surface. In this study, through experiments and numerical simulations, a pulsatile phenomenon was found in the velocity and concentration distribution of the unsteady buoyant jet. Results show that the contaminate escape ratio is pulsatile; it rises with the instantaneous increase in the buoyant jet velocity and gradually decreases to a constant value. This study not only reveals the air distribution of pulsating buoyant jet but also analyses the effect of the pulsating buoyant jet and high-temperature plume on lateral ventilation system capture efficiency and provides a possible guidance for future design of new building ventilation technologies.

To meet the ventilation requirement, an engineer needs to design the cantilevered roof of a stadium as a layered one with gaps between the layers. In order to further understand the wind resistance performance of such structures, a wind tunnel test was carried out on a 1:200 scaled stadium model considering two roof inter-layer cases: opened gaps and blocked gaps. The laws of lift force coefficients and net wind pressure coefficients were compared for these two gap conditions. The study results indicate that the roof experiences larger mean lift force on both top and bottom surfaces when the inter-layer gaps are blocked. However, the roof gaps can reduce the fluctuating lift force on top roof surface and the net fluctuating lift force, weakening the vibration of the flexible large-span roof. The negative pressures (suctions) in the inner and middle roof areas on the leeward side decrease for the blocked gap case. The positive pressure in the outer roof area generally increases along the windward direction, while the negative pressure decreases in other wind directions, when the roof inter-layer gaps are blocked. In the highest and transition roof areas, the fluctuating pressures increase for most wind directions, while in the lowest roof area, they decrease when the roof inter-layer gaps are blocked. The test and analysis results provide a valuable basis for the wind design of this kind of roof structures.

Ventilation and air conditioning system in subway stations accounts for about 50% of the total energy consumption of the subway stations. The energy consumption ratio of public area to equipment room is about 6.5:3.5. In order to understand the energy saving potential of public areas and equipment rooms, a field measurement for a typical subway station in central China was conducted from 19 to 29 September 2018. The field testing parameters include weather conditions, indoor air temperature and humidity, supply and return air flow rate, chilled water temperature, and flow rate. Meanwhile, some parameters recorded by the system control panel, such as pump frequency, chiller power demand, and energy consumption, were also collected. The paper studied the operating characteristics of the ventilation and air conditioning system and the cooling load pattern of the subway station, focusing on the following three aspects: cooling capacity and power demand of the chiller under different conditions, dynamic cooling capacity of the air handling units, and cooling load characteristics of the equipment rooms. Different operation conditions influence the operation of chiller. It was found that the real power demands under two operation conditions, i.e. minimum and all fresh air modes, are 121 and 77 kW, and the corresponding coefficient of performances are 4.33 and 4.77, respectively. The actual cooling capacity at night is about 80% that of the daytime, and is about 40% of the design value, which indicates that the air handling units operate under partial load. During the testing period, the actual cooling load is about 10–50% of the design load, of which 50–95% is sensible cooling load. These data can help readers understand the overall situation of a typical subway station adequately and provide numerical basis for energy saving optimization of the ventilation and air conditioning system.

Dynamic optimal airflow ventilation can have a great impact on the indoor air distribution and pollutant removal to improve the indoor air quality while saving energy. An online monitoring and control ventilation system has been developed and evaluated using fast prediction models and micro-control. An environmental chamber (1.8 m3) was used for the evaluation to monitor the CO2 dispersion under different air change rates and air speed. Specifically, an artificial neural network model based on a low-dimensional linear ventilation model was introduced and validated to provide environmental control and rapid prediction of pollutant concentration distribution in the indoor environment, which can save computing time and significantly enhance energy saving efficiency up to 16–47%. The validation was carried out by comparison with measurement data of the chamber experiment. An induction system was applied to locate and monitor the personnel in the office due to pollution that are generated by people. A ZigBee wireless module would transmit location information of pollutant source (i.e. CO2 generated by occupants) and to determine the optimal ventilation mode based on ventilation assessment to achieve automatic control of indoor air quality to ensure the wellbeing of occupants while saving energy.

This paper presents a case study to compare the zone-level actual supplied ventilation rate with minimum required ventilation rate for a typical variable air volume (VAV) operation. The minimum required ventilation rate was computed using zone-level actual occupancy, plug and lighting load data. Two different algorithms were adopted to collect the actual zone-level occupancy information using camera-based technology which are (a) area-based occupancy counting and (b) row-based occupancy counting. Similarly, zone-level Plug, lighting and air-conditioning and mechanical ventilation (ACMV) system-related energy data were taken from the energy submeters and BTU meters. The median values of actual supplied ventilation rates are 0.16, 0.14, 0.14 and 0.12 m3/s for the classroom, computer room, open office and closed office, respectively. For the same zone, the computed minimum required ventilation rates are 0.10, 0.09, 0.10 and 0.08 m3/s, respectively. This case study shows that except during evening classes in classroom and computer room, the actual ventilation supplied is much more than the minimum required ventilation. These over and under ventilation scenarios have been identified as an indicator for energy wastage and poor indoor environmental quality, respectively.

The purpose of this paper is to explore the influence of enclosed auditorium types on the wind ventilation environment inside a large semi-outdoor stadium. Stadia can be divided into three basic forms: all enclosed type auditorium, two sided and three-sided type auditorium. Different forms could have different effects on the wind environment inside a stadium, and the wind environment could have an impact on the competition in the stadium. In this study, a computer simulated hydrodynamics technology was used to model the stadium in different enclosed auditorium types. The wind environment in the stadium under different ventilation angles was simulated. The study found that for all round type stadia, the best inlet wind angle for the stadium ranges from 75° to 90°, which would avoid high wind velocity influences. For two-sided auditorium type stadia, 100 m sprinting track should be placed at the position near the auditorium. For inlet wind direction, 60° to 90° are the best inlet wind angles most favourable for sports competition. Hence, different stadium forms correspond different optimal inlet wind angles, while sport competition would also be impacted by the wind flow condition inside stadium.

Based on air flow rate testing of each branch fan in a distributed fan ventilation system under different branch air duct inlet static pressures, the conclusion can be drawn that there is a branch fan air flow rate deviation phenomenon. The air flow rate of the branch fan increases with the branch air duct inlet static pressure at the same branch fan speed, and the branch fan hinders the air flow rate in some cases. In this study, a theoretical expression of the deviation of the branch air duct design air flow rate was established, and the influencing factors of the deviation were determined to include the branch air duct resistance characteristics, branch fan performance, and branch air duct inlet pressure ratio. A graphic analytical method for determining the deviation of the branch fan design air flow rate was also proposed. Both methods can provide a theoretical basis for calculating and analysing the deviation of the branch fan design air flow rate in a distributed fan ventilation system. Practical application: This paper provides new data on the performance of a distributed fan ventilation system. Our results could be used to evaluate the impact of distributed zone fans on the air flow rate in a mechanical ventilation system. Crucially, we not only propose two types of methods that can be applied to predict deviations of the air flow rate in a distributed fan ventilation system caused by the branch air duct inlet static pressures but also obtain the factors that are important for understanding the true impact of the deviation of the branch fan air flow rate. This study lays an important foundation for the design and operation of building mechanical ventilation systems.

Nowadays, the critical velocity and back-layering length are the key parameters in longitudinal ventilation design. However, most studies research them at standard air pressure but ambient pressure decreases at high-altitude area and the reduced ambient pressure could affect the smoke movement characteristics in a tunnel fire. In order to investigate the effect of ambient pressure on the velocity and back-layering length in longitudinal ventilated tunnel, theoretical analysis was carried out first and a series of numerical simulation were conducted with varying heat release rate and ambient pressure. Results show that Li’s model is also reliable under various ambient pressures. The critical velocity under various ambient pressures would become larger with an increase in the heat release rate and would remain stable after the heat release rate reaches a certain value. At smaller heat release rate, the length of counterflow would be higher under reduced ambient pressure while it remains the same when the HRR is large. This could provide reference for tunnel ventilation design at high-altitude areas.

This study conducted a series of computational fluid dynamics simulations to evaluate the thermal comfort performance of a radiant floor cooling system when combined with different ventilation systems, including mixed ventilation (MV), stratum ventilation (SV), displacement ventilation (DV) and ductless personalized ventilation (DPV). A window temperature of 32°C and three different floor temperatures including 20, 22 and 24°C were set in summer. We used the vertical air temperature differences (VATD) at ankle and head level, the percentage of dissatisfied, the draught rate at the ankle level and the equivalent temperature as our main evaluation indices. Our results show that the VATD in DV system can reach up to about 5°C, compared with about 2°C in MV and SV systems. For the DPV system, there is only a marginal drop in the VATD. For the DV and DPV cases, with a rate of air changes per hour (ACH) of 2.4−1, we recorded a higher draught rate at the ankle level, ranging from 6.55% to 9.99%. The lower equivalent temperature values for the foot and calf segments occur when the floor temperature is 20°C. In all cases, the equivalent temperature values of the whole body indicate an acceptable level of thermal discomfort.

Few studies have investigated the thermal environment of the work area hall in underground metro stations during winter. Two underground stations were chosen within Qingdao Metro Lines 2 and 3 to investigate the thermal environment in the work area hall in northern city metros in China. Air temperatures and wind velocity parameters were identified as key influencing factors and were continuously measured in the work area. The study found that the thermal environment fluctuates frequently in the work area throughout the day. Changes in temperatures and wind speeds were periodically caused by piston wind flowing from the platform level. To improve this heating situation in the work area in winter, the study proposes recycling waste heat from the power equipment rooms, using the air source but through the water cycle heat pump system. Insights from the study may help save energy and improve the thermal environment, and could be applied across metro stations in north China cities in winter. Practical application: The thermal comfort of the working area in the metro station hall is extremely poor as indicated by a study of Qingdao Metro stations. This paper explores the application of a heat pump as a means of heating the working area to improve the cold and damp winter environment for the metro staff using waste heat from the machine rooms.

Modern diesel engine aftertreatment systems require elevated temperatures for effective reduction of engine-out emissions. Maintaining elevated aftertreatment temperatures in a fuel-efficient manner is a challenge, especially at low-load engine operation where engine-outlet temperatures are low; therefore, higher engine-outlet temperatures are typically achieved via increased fuel consumption. Previous studies have demonstrated that strategies such as cylinder deactivation (method where there is neither valve motion nor fuel injection in a subset of cylinders, thereby isolating the deactivated cylinders from the gas exchange process) and cylinder cutout (method where there is no fuel injection in a subset of cylinders, implemented with high recirculated gas rates) reduce fuel consumption while elevating engine-outlet temperatures, by reducing the overall airflow through the engine. This article introduces and characterizes “non-fired cylinder ventilation” as alternate means to achieve fuel-efficient aftertreatment thermal management, by reduction of overall airflow through the engine. Fuel injection is deactivated from a subset of cylinders during non-fired cylinder ventilation, and the non-firing cylinders participate in the gas exchange process with the same manifold at a time, thereby reducing the intake-to-exhaust manifold gas exchange through the cylinders. It is demonstrated that non-fired cylinder ventilation shows similar fuel efficiency and thermal management as cylinder deactivation when the valves of the non-firing ventilated cylinders are open by at least 4 mm, due to similar, negligible, gas-exchange losses, while non-fired cylinder ventilation with lower valve lifts enables elevated engine-outlet temperatures with relatively higher fuel consumption than cylinder deactivation. Non-fired cylinder ventilation strategies demonstrate 75 °C higher temperatures at fuel-neutral conditions, and up to 35% fuel savings at similar temperatures, compared to six-cylinder operation.

The total energy consumption of buildings in China has been increasing year by year, ventilation energy consumption accounts for more than 20% of the total building energy consumption. The optimisation of ventilation system design aiming at energy conservation is of great significance while keeping healthy indoor air quality. However, the current codes and standards are still lacking specification requirements for vents design, e.g. inlet size ratio or position, which can greatly impact on indoor airflow and ventilation efficiency. In this work, we investigated the aspect ratios of vent inlets and their locations on indoor air quality. Both experimental and numerical simulation methods were adopted. Ventilation efficiency is represented with the local average peak concentration 〈C ̅*〉A,max. Results showed that when vent inlet is in symmetric conditions (i.e. located in the middle of the sidewall) and the aspect ratio between the length and width of the vent inlet equals to 4, ventilation removal efficiency showed the best performance. These findings are of great importance to the engineering applicability and able to provide reference for future design standards.

© The Author(s) 2019. Hermetic digital scroll compressor has been widely used as a small-scale organic Rankine cycle application in the heating, ventilation, and air conditioning systems. A clunking noise issue is recently found in an air conditioning outdoor unit, and the main cause of the noise is experimentally identified to be the impact of the scrolls in the compressor unit during the switching process. The semi-active control methods are thus designed to greatly reduce the noise level by using additional valves to adjust the pressure changing rate within the modulation chamber. The response time for the impact of the scrolls can then be controlled by the added valves. The additional release valve with a smaller diameter pipe parallel to the main valve is tested firstly for its performance. Slower flow rate is produced and the pipe can extend the response time and decrease the speed of the impact process by reducing the pressure changing rate. The use of a discharge valve is also tested for controlling the pressure changing rate inside the chamber. The discharge valve with an opposite effect to the release valve is found useful for solving the noise issue. Both noise and vibration results confirm that the impact noise in the frequency range of interest can be reduced by using the proposed semi-active control methods.

Thermal comfort is closely related to the evaluation of heating, ventilation, and air conditioning systems. It can be seen as the result of the perception of the occupants of a given environment, and it is the product of the interaction of a number of personal and environmental factors. Otherwise, comfort issues still do not play an important role in the daily operation of commercial buildings. However, in the workplace, local quality effects, in addition to the health, the productivity that has a significant impact on the performance of the activities. In this regard, researchers have conducted, for decades, investigations related to thermal comfort and indoor environments, which includes developing models and indices through experimentations to establish standards to evaluate comfort and factors and set-up parameters for heating, ventilation, and air conditioning systems. However, to our best knowledge, most of the research work reported in the literature deals only with parameters that are not dynamically tracked. This work aims to propose a prototype for comfort measuring through a wireless sensor network and then presenting a model for thermal comfort prediction. The developed model can be used to set up a heating, ventilation, and air conditioning system to meet the expected comfort level. In particular, the obtained results show that there is a strong correlation between users’ comfort and variables such as age, gender, and body mass index as a function of height and weight.

To solve the challenges of high labour and maintenance cost while saving energy in engineering, a decentralized agent-based model-free global optimization method for heating, ventilation and air conditioning systems is proposed. In this novel optimization method, each updated smart equipment is connected according to the physical relationships, such that it can communicate and collaborate with adjacent nodes. Furthermore, to achieve the overall optimal operation of heating, ventilation and air conditioning systems, a decentralized evolutionary algorithm is developed. With the decentralized algorithm executed in all smart nodes in parallel with the feedback of sensor measurements instead of accurate device models, the system can achieve optimal coordination and avoid conflicts between correlated devices. The equivalence between the centralized and decentralized methods is proven. This method is confirmed to be effective through hardware testing based on actual engineering. Practical application: The traditional optimization methods for heating, ventilation and air conditioning are based on a centralized structure with a series of deficiencies, such as high maintenance and labour costs, link congestion and operational lag. This study presents a novel decentralized structure constructed using basic physical relations and a model-free method that possesses the advantages of plug-and-play, rapid development, great flexibility and convenience for engineering implementation without having to build a central monitor. The case study results validate the efficiency and effectiveness of the proposed method.

Indoor air pollution level in dwellings varies in different areas. Specifically, the formaldehyde and total volatile organic compound pollution are serious in new residential buildings according to the investigation of indoor air pollution status of residential buildings in China. Appropriate ventilation, as an important means to reduce the concentration of indoor pollutants, is mainly affected by ventilation mode, ventilation performance, ventilation strategies, etc. This paper analyses the status, standards, technologies and products related to residential ventilation and concludes the existing drawbacks in residential ventilation applications in China. Understanding of residential ventilation, and its standards, design methods, technologies, products, also the economy and usability should be given a major consideration to research.