Room Ventilation Research Articles

Dietary habit and lifestyle of postpartum women in South China: a mixed methods research

ObjectiveTo investigate the dietary and hygiene behaviours and influencing factors of women during the puerperium in South China.DesignA cross-sectional study.SettingThree tertiary hospitals in Guangdong Province, ChinaParticipantsFrom November 2022 to March...

Development of operable modular louvers Sited in a single-sided ventilated room through 3D parametric optimization

The current design practices of buildings to respond to environmental inputs have led to operable envelopes with external louver blinds systems. The key aspect of any openable louver flap design is to optimize inlets that might induce ventilation for occupants with low indoor airflow. Computational Fluid Dynamics (CFD) in 3D parametric modeling investigated the influence of openable louver inlet geometries (right trapezoid) and positions in a ventilated room. A single-sided ventilated room designed with two mirrored split blocks of inlets attached to that wall perpendicular to the wind was employed for this study. Twenty-eight different inlet shape geometries with their cross-sectional changes were investigated. In addition, the inlets' rotation, orientation, and elevation differences were also studied. Wind tunnel experiments were conducted to measure airflows inside the model room to validate the CFD simulations. A discernible impact was observed when the inclined side of the right trapezoid was oriented upward or downward, where inlet flaps open to the sides of the window. The mean air velocity in the ventilated room becomes more than double when inlet flaps open to the sides of the window, where the elevation difference in the inlet blocks introduces the pressure difference compared to no elevation difference in inlets. This study guides into refining an operable modular louver design to enhance air circulation and natural ventilation in dwelling spaces.

A Numerical Evaluation of Airborne Transmission Control through Saliva Modification

The present study explored the relationship between airborne transmission and the saliva fluid properties of a human sneeze. Specifically, we aimed to understand if altering the saliva and its relationship to droplet breakup and stability can affect its transmission characteristics. The study aimed to answer this question using computational fluid dynamics, specifically, a hybrid Eulerian–Lagrangian model with a Spalart–Allmaras, detached eddy simulation turbulence model. The effort focused on a scenario with a sneeze event within a ventilated room. The study found that for sneezes, secondary breakdown processes are important. Thicker saliva that increased the Ohnesorge number displayed a clear resistance to aerosolization due to stabilized secondary breakup, leading the bulk of the drops having high settling rates that are less likely to drive airborne transmission. For instance, the use of xanthum gum, which increased the saliva viscosity by 2000%, reduced the formation of aerosols. Additionally, another class of modifiers that reduce saliva content was studied, which was also effective in reducing airborne transmission drivers. Zingiber, which reduced the saliva content, reduced the formation of aerosols. However, when considering the overall reduction in droplet volume, saliva modifiers such as cornstarch, xanthum gum, and lozenges increased the mean droplet size by 50%, 25%, and 50%, respectively, while reducing the overall droplet volume by 71.6%, 71.2%, and 77.2%, respectively. Conversely, Zingiber reduced the mean droplet size by 50% but increased the overall droplet volume by 165.7%. Overall, for this type of respiratory event, this study provides insight into the potential for modifying saliva characteristics that may impact airborne transmission and could introduce new tools for reducing airborne pathogen transmission.

Numerical study using the finite volume method on the thermal and energy performance of a regulated underfloor heating system incorporating PCM in a ventilated room

A physical model is performed to assess the thermal and energetic advantages of using PCM in controlling and regulating the indoor temperature of a ventilated room with an underfloor heating system incorporating a PCM. The heating source is regulated to keep the cavity air temperature in a small interval assuring a certain level of comfort without wasting too much energy. By contrasting our numerical results with numerical data from the literature, the suggested model was validated. Physical processes are solved numerically using computational fluid dynamics by a detailed 2D transient simulation integrating real climatic data of Agadir, Tangier and Casablanca. The simulations carried out justified the suitability of using the PCM with Agadir and Casablanca climate types by a saving of heating power reaching 18.80 % and 17.33 %, respectively.

A comparative study on germination of wheat grains with different anthocyanin pigmentation of the pericarp in natural or induced aging.

One of promising areas of wheat breeding is the creation of varieties with a high concentration of anthocyanins in the grain for the production of functional food products. Nonetheless, the question of how these compounds affect seed viability after long-term storage has remained unexplored. A comparative study on seed viability was conducted using a set of near-isogenic lines on the background of spring wheat variety Saratovskaya 29. These sister lines carry different combinations of recombinant DNA regions (on chromosomes 2A and 7D) containing dominant and recessive alleles at loci Pp3 and Pp-D1 (Pp: Purple pericarp), which determine the anthocyanin color of coleoptiles and of the pericarp. Seeds were germinated on two layers of water-moistened filter paper in a climatic chamber at a constant temperature of 20 °C on a 12-hour daylight cycle. During long-term natural storage of the seeds for up to 9 years in a dry ventilated room in Kraft bags at 20 ± 2 °C, the tested wheat samples experienced a loss of seed germination capacity of ~50 %; anthocyanins were found to not participate in the preservation of germination capacity. Nonetheless, anthocyanins contributed to the preservation of seed viability under unfavorable short-term conditions of a temperature rise to 48 °C at 100 % humidity. The accelerated aging test did not predict poor germination capacity after long-term seed storage. The results showed a neutral role of anthocyanins in the maintenance of seed germination capacity for 6-9 years under natural storage conditions at 20 ± 2 °C. A small statistically significant increase in grain germination capacity during natural aging was associated with the presence of a recombinant region containing the Pp-D1 gene on wheat chromosome 7D.

Airflow and aerosol transport in the hospital isolation zone based on dynamic scenarios

To contain the leakage of viral aerosols, buffer rooms are usually provided in front of isolation wards. However, dynamic events of door movement and healthcare worker (HCW) walking will result in highly concentrated aerosols intruding into the buffer room from the ward, challenging the control of virus transmission risk. In this work, airflow exchange and bioaerosol particle transport between the negative-pressure isolation ward and the buffer room under dynamic scenarios were studied by transient computational fluid mechanics (CFD) simulation, thereby the fate of particles was divided into invasion stage and decay stage. The effects of ventilation pattern and HCW location on the concentration level and attenuation trend of particles were quantitatively analyzed. The results showed that increasing the HCW walking distance could increase the peak particle concentration within the buffer room by 4.5 % during the invasion stage. The effect of the buffer room ventilation layout on air exchange and particle transport was more pronounced than the HCW stay position. In the decay stage, the two more effective ventilation layouts could decrease the complete clearance time of particles and the particle concentration in the breathing zone by 31 % and 42 %, respectively. To reduce the infection risk, bioaerosol levels need to be reduced both in the buffer room and in the HCW breathing zone.

Relationship between Exhaled Aerosol and Carbon Dioxide Emission Across Respiratory Activities.

Respiratory particles produced during vocalized and nonvocalized activities such as breathing, speaking, and singing serve as a major route for respiratory pathogen transmission. This work reports concomitant measurements of exhaled carbon dioxide volume (VCO2) and minute ventilation (VE), along with exhaled respiratory particles during breathing, exercising, speaking, and singing. Exhaled CO2 and VE measured across healthy adult participants follow a similar trend to particle number concentration during the nonvocalized exercise activities (breathing at rest, vigorous exercise, and very vigorous exercise). Exhaled CO2 is strongly correlated with mean particle number (r = 0.81) and mass (r = 0.84) emission rates for the nonvocalized exercise activities. However, exhaled CO2 is poorly correlated with mean particle number (r = 0.34) and mass (r = 0.12) emission rates during activities requiring vocalization. These results demonstrate that in most real-world environments vocalization loudness is the main factor controlling respiratory particle emission and exhaled CO2 is a poor surrogate measure for estimating particle emission during vocalization. Although measurements of indoor CO2 concentrations provide valuable information about room ventilation, such measurements are poor indicators of respiratory particle concentrations and may significantly underestimate respiratory particle concentrations and disease transmission risk.

Assessment on the Exposure of Air, Water and Noise Pollution, and Mental Stress on Preeclamptic Patients of Rajshahi, Bangladesh

Although preeclampsia claims the lives of 70,000 mothers and 500,000 newborns each year worldwide, its origin is still elusive and a number of risk factors such as environmental pollution are not yet addressed properly. In this study, exposures due to the extents of air, water and noise pollution as well as mental stress on preeclamptic patients have been investigated. Using a cross-sectional longitudinal design, 90 women hospitalized with preeclampsia in 7 hospitals of Rajshahi, Bangladesh were considered, of which Rajshahi Medical College Hospital is a tertiary referral hospital. The data were collected by interviewing the patients, physical examinations and merging the patients’ data with British Geological Survey’s groundwater data-sets (n=3,540). For statistical analyses, SPSS software was employed. It was found that most of the patients’ living rooms were within 15 feet from kitchen. Only 10% patients had good room ventilation, while the remaining 90% patients had either moderate or poor room ventilation. Combination of these facts reveals that the preeclamptic patients were subject to moderate CO2 exposure. Since 79% of the preeclamptic patients’ living rooms were below 50 ft from the nearest roads and 84% for 100 ft distance, they would experience noise pollution. Combination of traffic conditions and potential sources of noise pollution revealed that 60% of the preeclamptic patients experienced moderate to intense noise pollution. Groundwater arsenic, calcium, magnesium, iron and sodium concentrations in the patients’ drinking water were higher than WHO guideline values that should favour constipation and mild hypertension. While 70% patients were under high mental stress and 24% under very high mental stress, only 6% patients had moderate mental stress. It is concluded that air, water and noise pollution, and mental stress are potential risk factors of preeclampsia.

A coronavirus disease 2019 outbreak in a residential living facility with suboptimal ventilation in resident rooms

We report a large outbreak of severe acute respiratory syndrome coronavirus 2 in a residential living facility. Measurements of carbon dioxide levels, aerosol particle clearance, and airflow were used to identify and remediate areas with suboptimal ventilation. A simple intervention involving continuous operation of bathroom fans was effective in significantly improving ventilation in resident rooms.

Research on natural ventilation of a community library related to epidemiological insight by using CFD simulation method

Abstract Spreading through airflow is one of the most common routes for the transmission of viruses, which may result in serious public health problems. To acquire a healthy space for the community library, designing a reasonable ventilation system is a vital measure which can reduce the risk of transmission of the virus effectively. The purpose of this research is to study natural ventilation methods in an epidemiological insight for the design of a healthy community library by using computational fluid dynamics (CFD) software SOLIDWORKS Flow Simulation. Five typical opening types of windows were selected and studied in the research on the ventilation of the yoga room of a community library, with airflow evaluated by the ACH method, so as to search for the most suitable window type to avoid airborne virus transmission. The results acquired by SOLIDWORKS simulation showed that 75%, 90%, and 100% openings corresponding to Jalousie, casement, and double casement window types respectively are optimal in community space. The natural ventilation design by proper windows can be applied in the community library and other public spaces.

Association between initial ventilation mode and hospital outcomes for severe congenital diaphragmatic hernia

ObjectiveTo determine the association between initial delivery room (DR) ventilator (conventional mechanical ventilation [CMV] versus high frequency oscillatory ventilation [HFOV] and hospital outcomes for infants with severe congenital diaphragmatic hernia (CDH).Study designQuasi-experimental design before/after introducing a clinical protocol promoting HFOV. The primary outcome was first blood gas parameters. Secondary outcomes included serial blood gas assessments, ECMO, survival, duration of ventilation, and length of hospitalization.ResultsFirst pH and CO2 were more favorable in the HFOV group (n = 75) than CMV group (n = 85), median (interquartile range (IQR)) pH 7.18 (7.03, 7.24) vs. 7.05 (6.93, 7.17), adjusted p-value < 0.001; median CO2 62.0 (46.0, 82.0) vs 85.9 (59.0, 103.0), adjusted p-value < 0.001. ECMO, survival, duration of ventilation, and length of hospitalization did not differ between groups in adjusted analysis.ConclusionAmong infants with severe CDH, initial DR HFOV was associated with improved early gas exchange with no adverse differences in hospital outcomes.

Formation and Transport of Secondary Contaminants Associated with Germicidal Ultraviolet Light Systems in an Occupied Classroom.

Germicidal ultraviolet light (GUV) systems are designed to control airborne pathogen transmission in buildings. However, it is important to acknowledge that certain conditions and system configurations may lead GUV systems to produce air contaminants including oxidants and secondary organic aerosols (SOA). In this study, we modeled the formation and dispersion of oxidants and secondary contaminants generated by the operation of GUV systems employing ultraviolet C 254 and 222 nm. Using a three-dimensional computational fluid dynamics model, we examined the breathing zone concentrations of chemical species in an occupied classroom. Our findings indicate that operating GUV 222 leads to an approximate increase of 10 ppb in O3 concentration and 5.2 μg·m-3 in SOA concentration compared to a condition without GUV operation, while GUV 254 increases the SOA concentration by about 1.2 μg·m-3, with a minimal impact on the O3 concentration. Furthermore, increasing the UV fluence rate of GUV 222 from 1 to 5 μW·cm-2 results in up to 80% increase in the oxidants and SOA concentrations. For GUV 254, elevating the UV fluence rate from 30 to 50 μW·cm-2 or doubling the radiating volume results in up to 50% increase in the SOA concentration. Note that indoor airflow patterns, particularly buoyancy-driven airflow (or displacement ventilation), lead to 15-45% lower SOA concentrations in the breathing zone compared to well-mixed airflow. The results also reveal that when the ventilation rate is below 2 h-1, operating GUV 254 has a smaller impact on human exposure to secondary contaminants than GUV 222. However, GUV 254 may generate more contaminants than GUV 222 when operating at high indoor O3 levels (>15 ppb). These results suggest that the design of GUV systems should consider indoor O3 levels and room ventilation conditions.

Numerical Analysis of the Effects of Different Window-Opening Strategies on the Indoor Pollutant Dispersion in Street-Facing Buildings

The idling of automobiles at street intersections can lead to pollutant accumulation which impacts the health of residents in street-facing buildings. Previous research focused on pollutant dispersion within street canyons and did not consider the coupling of indoor and outdoor pollutants. This paper employs the computational fluid dynamics (CFD) method to simulate the dispersion characteristics of vehicle emission pollutants in street canyons, primarily investigating the indoor and outdoor pollutant dispersion patterns under various window opening configurations (single-sided ventilation, corner ventilation, and different positions of the glass under corner ventilation). Additionally, the study considers the impacts of the aspect ratio and ambient wind speed. Studies have shown that corner ventilation is effective in reducing indoor pollutant levels. When the two window glass positions are far away from the center of the intersection, the average CO mass fraction in the single-sided ventilation room is reduced by 87.1%. The average indoor CO mass fraction on the leeward side decreases with the increasing wind speed and aspect ratio. At a wind speed of 8 m/s, the average indoor CO mass fraction on the leeward side decreases to 2.45 × 10−8. At an aspect ratio of 2, the indoor CO mass fraction on the leeward side decreases with increasing floors before stabilizing at approximately 4.77 × 10−9. This study suggests optimal window opening strategies to reduce indoor pollutant levels in street-facing buildings at street intersections, offering guidance to indoor residents on window ventilation practices.

Use of mask ventilation and oxygen supplementation in German delivery rooms from 2008 to 2022.

Use of mask ventilation and oxygen supplementation in German delivery rooms from 2008 to 2022.

Investigation of infectious droplet dispersion in a hospital examination room cooled by split-type air conditioner

The novel coronavirus (SARS-CoV-2) outbreak has spread worldwide, and the World Health Organization (WHO) declared a global pandemic in March 2020. The transmission mechanism of SARS-CoV-2 in indoor environments has begun to be investigated in all aspects. In this regard, many numerical studies on social distancing and the protection of surgical masks against infection risk have neglected the evaporation of the particles. Meanwhile, a 1.83 m (6 feet) social distancing rule has been recommended to reduce the infection risk. However, it should be noted that most of the studies were conducted in static air conditions. Air movement in indoor environments is chaotic, and it is not easy to track all droplets in a ventilated room experimentally. Computational Fluid Dynamics (CFD) enables the tracking of all particles in a ventilated environment. This study numerically investigated the airborne transmission of infectious droplets in a hospital examination room cooled by a split-type air conditioner with the CFD method. Different inlet velocities (1, 2, 3 m/s) were considered and investigated separately. Besides, the hospital examination room is a model of one of the Bursa Uludag University Hospital examination rooms. The patient, doctor, and some furniture are modeled in the room. Particle diameters considered ranged from 2 to 2000 μm. The evaporation of the droplets is not neglected, and the predictions of particle tracks are shown. As a result, locations with a high infection risk were identified, and the findings that could guide the design/redesign of the hospital examination rooms were evaluated.

Numerical study on the internal ventilation of the engine room of a ship under construction

Manual welding operations are performed inside the engine room of a liquefied natural gas carrier under construction. The welders are at risk of exposure to welding fumes in case of poor ventilation. Therefore, ventilation fans are installed at shipbuilding sites to improve indoor air quality. Although ensuring the respiratory health of welders is important, studies focusing on ventilation in the ship engine room have not been conducted. Therefore, the ventilation efficiency was evaluated herein based on the placement of ventilation fans to alleviate air stagnation using a computational fluid dynamic (CFD) model operating on Fluent. The mean age of air (MAA) was computed to assess the ventilation efficiency. In addition, particles with size and physical properties similar to welding fumes were sourced assuming 30 welders in the engine room. Results revealed that ventilation fan and/or exhaust in enclosed spaces contributes significantly to alleviating the MAA level. MAA and particle distribution did not correlate well due to the different properties of air and the iron oxide particle. Therefore, to determine the optimal ventilation fan displacement, particle motion should be studied along with performing MAA analysis. The proposed CFD model potentially guides to improvement of the working environments and respiratory health of welders.

Effectiveness of natural ventilation through single-sided window opening in air-conditioning rooms

Since many buildings are not equipped with fresh air systems, many people open windows to allow for natural ventilation while the air conditioner is running. However, prolonged window opening may cause unnecessary energy consumption. Additionally, the diverse ways of window opening lead to significant variations in indoor airflow distribution, consequently impacting ventilation efficiency. Therefore, this study used field experiments and computational fluid dynamics (CFD) to determine the air exchange efficiency and air change rate of single-sided natural ventilation in air-conditioning rooms by fitting the decay curves of tracer gas. CFD simulation was performed using the unsteady Reynolds-averaged Navier-Stokes (RANS) model to examine how window openings affect the room’s air distribution, and the computed indoor CO2 concentration was compared to the corresponding field experiment data. The results show that natural ventilation through the window opening induced constant heat and mass exchange between indoor and outdoor air, which caused extra cooling losses but was globally effective in eliminating indoor contaminants. The air exchange efficiency is influenced to varying degrees by factors such as the air supply register’s position, window opening percentage, and window opening position. The air supply register’s position exerted the most significant impact at 46.45%. Efficient indoor-outdoor air exchange can be achieved by opening windows intermittently. When the window is opened from one side and the opening percentage is 100%, the indoor environment can be improved by opening the window for about 10 min every 39 min for X-direction air supply and about 7 min every 39 min for Y-direction.

Resolving the Loss of Intermediate-Size Speech Aerosols in Funnel-Guided Particle Counting Measurements

Modeling of airborne virus transmission and protection against it requires knowledge of the amount of biofluid emitted into the atmosphere and its viral load. Whereas viral concentrations in biofluids are readily measured by quantitative PCR, the total volume of fluids aerosolized during speaking, as measured by different researchers using various technologies, differs by several orders of magnitude. We compared collection methods in which the aerosols first enter into a low-humidity chamber either by direct injection or via commonly used funnel and tubing arrangements, followed by standard optical particle sizer measurement. This “collect first, measure later” approach sacrifices the recording of the temporal correlation between aerosol generation and sound types such as plosives and vowels. However, the direct-injection mode prevents inertia deposition associated with the funnel arrangements and reveals far more intermediate-size (5–20 μm in diameter) particles that can dominate the total mass of ejected respiratory aerosol. The larger aerosol mass observed with our method partially reconciles the large discrepancy between the SARS-CoV-2 infectious dose estimated from superspreader event analyses and that from human challenge data. Our results also impact measures to combat airborne virus transmission because they indicate that aerosols that settle faster than good room ventilation rates can dominate this process.

Humidity regime of building envelope structures of the drying compartment tula brewery

The article presents the results of a study of the humidity regime of building enclosing structures of the drying department of the brewery located in Tula. The assessment of the humidity regime was carried out in order to identify the causes of damage to external, internal walls and attic floors, and the task was also set to develop technical solutions for steam and waterproofing of the above-mentioned enclosing structures. To solve the tasks set, thermophysical calculations of building enclosing structures were performed, as well as an assessment of their moisture accumulation during the operation of the building. The position of the plane of possible condensation was determined using the author’s methodology. The results of thermophysical calculations showed the presence of moisture accumulation in the above-mentioned structures, which is associated with the use of PVC polyethylene film as wind protection. It was also revealed that there was a discrepancy with the regulatory requirements for thermal protection of the external wall of the electrical panel. In order to eliminate these problems, recommendations were made, which consisted in using an Isospan A type film as a vapor barrier, increasing the thickness of the insulation, organizing natural supply and exhaust ventilation of the attic room, as well as waterproofing the structures of the outer wall made of monolithic reinforced concrete.

Conversion of a regular patient room to negative pressure at Ancona university hospital (Italy). A combined experimental and numerical investigation

Negative pressure isolation rooms are employed to prevent the spread of infectious diseases to surrounding spaces. This study reports a combined experimental and numerical analysis aimed at reliably assessing the performance of hospital ventilation systems and effectively reducing the risk of airborne infections. The study appraises the enhancement of the safety conditions by retrofitting an existing, positive pressure room ventilation system with a negative pressure and recirculation one. The assessment consisted in experimental measurements of airborne particle concentration and Computational Fluid Dynamics (CFD) simulations with Lagrangian particle tracking of respiratory droplets. The ventilation performance improvement was quantified in terms of recovery rate, contaminant removal effectiveness, particle transfer toward adjacent spaces and probability of infection.Two experimental campaigns were carried out: an ISO standard recovery assessment and a test in real operational conditions. The negative pressure configuration significantly improved the safety inside the patient ward: the recovery rate for droplets with diameter larger than 5 μm increased by a factor three, and the contaminant removal effectiveness after 15 min increased from 45% to 81%. The numerical model for Computational Fluid Dynamics simulation was successfully validated, confirming the ability of the approach to reproduce the undergoing Physics. The negative pressure design eliminated the particle transmission to surrounding spaces, while 2.5% of the emitted respiratory droplets escaped the room in the original existing scenario. The probability of infection after 15 min exposure was reduced by a factor three and peak values reaching 15% were limited to the immediate vicinity of the patients.