Air conditioning, ventilation, and respiratory virus transmission potential in South India.

Despite the preweaning period being critical for immune system development, heat abatement for calves in summer is often overlooked during this early-life period. Herein, we evaluated selected markers of innate and adaptive immunity development in outdoor hutch-housed Holstein dairy heifers with 2 types of ventilation during a Midwestern summer. Heifer calves were housed in outdoor hutches with passive (PASS; 0.07 m/s natural air speed, n = 16) or active ventilation (ACT; 1.1 m/s air speed via solar-powered fans, n = 16) from birth to 28 d of life. At d 28, fans were turned off, and all heifers were naturally ventilated. Heifers were weaned at 49 d and monitored until 56 d of age. Blood samples were collected at various stages of the preweaning period (d 1-56) to assess IgG, glucose, blood hematology, gene expression, and functional assays. At birth, circulating IgG, glucose, and hematology parameters were not different between groups. Relative to heifers exposed to PASS, ACT heifers had reduced white blood cell, monocyte, neutrophil, and lymphocyte counts, particularly the first 28 d. The ACT heifers had a greater percentage of neutrophils with phagocytic activity on d 28 and 42 of life, and tended to have neutrophils with greater percentage of oxidative burst on d 42. The mRNA expression of haptoglobin, IL-6, IL-8, IFN-γ, and NFKβ1 was downregulated in peripheral blood leukocytes of PASS heifers, relative to ACT. Providing active ventilation to heifers during the first 4 wk of life in summer enhances neutrophil phagocytic capacity, reduces circulating neutrophil and lymphocyte counts, and downregulates the expression of key pro-inflammatory cytokine and interleukin genes in peripheral leukocytes.

Study on the mass flow rate of the ceiling jet in natural ventilation tunnel fires

ABSTRACT This study investigates the effects of balcony sliding-door arrangements and balcony window-opening configurations on natural ventilation performance in residential apartments using Computational Fluid Dynamics (CFD) simulations with FLUENT. Two representative apartment layouts, a two-bedroom unit and a three-bedroom unit, were modeled, and varying internal sliding door configurations, balcony window-opening arrangements, and wind directions developed fourteen scenarios. Field measurements of indoor air velocity were used to validate the numerical model. The results show that in the three-bedroom layout, the internal sliding door between the balcony and the living-dining area restricted airflow into the main shared space. Removing this internal sliding door and adopting operable balcony windows on both sides reduced the mean air age in the living area and improved airflow distribution. In contrast, in the two-bedroom layout, where the balcony was connected mainly to a bedroom, removing the balcony–bedroom sliding door did not consistently improve overall ventilation. Retaining the sliding door while optimizing the side-window openings on the balcony offered a more balanced approach. The findings suggest that balcony spaces should be treated as active components of residential ventilation, and the study provides design insights to improve natural ventilation.

Expression of Concern: A study on the temperature profile of bifurcation tunnel fire under natural ventilation

BackgroundGuidelines on neonatal resuscitation recommend 90 chest compressions (CCs) and 30 ventilations (3:1 C:V) per minute in newborns. We have described an alternative resuscitation strategy where CCs are superimposed with sustained inflation (CC + SI), which allows for passive ventilation during compression. A more recent strategy is CCs with synchronized ventilation (CCSV), in which a ventilator flow sensor recognizes airflow during the downward phase of compression and thereby triggers an inflation. No study has compared CCSV with CC + SI in an asphyxiated newborn piglet model. Newborn piglets (n = 8/group) were anesthetized, intubated, instrumented, and exposed to 45 min of normocapnic hypoxia, followed by asphyxia and asystolic cardiac arrest. Piglets were randomized to CCSV or CC + SI. Hemodynamic and respiratory parameters were continuously measured.ResultsSixteen neonatal mixed-breed piglets (1–3 days of age, weighing 1.7–2.8 kg) were randomized to CCSV or CC + SI. Median (IQR) time to ROSC was 68 (50–125) s with CCSV and 71 (60–178) s with CC + SI (p = 0.537). The rate of ROSC with CCSV compared to CC + SI was 6/8 (75%) vs. 5/8 (63%), respectively, p = 1.000. CCSV had significantly higher peak inflation pressure (45 vs. 36 cmH2O) and lower positive end-expiratory pressure (5.3 vs. 37 cmH2O) compared to CC + SI (both p < 0.001); tidal volumes were not significantly different.ConclusionsUse of CCSV did not result in a faster time to ROSC compared to CC + SI, and survival rates and physiological stability did not differ significantly.

Influence of fuel depth and sidewall restriction on combustion behavior of heptane pool fires in a short tunnel with natural ventilation

Radiative cooling coatings and natural ventilation in urban street canyons: Synergies and trade-offs

Worker exposure to bioaerosols from sludge dewatering facilities: risks and mitigations.

• Coupling of internal thermal mass with buoyancy ventilation, experimental validation • Wood and concrete thermal mass designs compared, both achieve optimal and equivalent performance • Both test buildings reach the same targets for temperature damping (0.7) and ventilation rate (20 L/s) • Surface area of wood thermal mass increased by × 1.42 to compensate for inferior thermal properties • Temperature damping drives reliable airflow in night updraft (28.1 ± 0.4 L/s) and day downdraft (16 ± 0.4 L/s) Right-sizing thermal mass in buildings is increasingly crucial for achieving climate resilience while curtailing both operational and embodied greenhouse gas emissions. In this study, we conducted a full-scale experiment to validate a theoretical approach to optimize the distribution of internal thermal mass in concert with natural buoyancy ventilation. Ventilation is driven by the indoor temperature damping (produced by the thermal mass), with upward flow at night and downward flow during the day. Two test buildings were constructed in Alabama, USA (ASHRAE climate zone 3A), to compare the performance of wood and concrete thermal mass in this temperature-ventilation cycle. The wood and concrete thermal masses achieved temperature damping of M = 0.74 ± 0.07 and M = 0.70 ± 0.07 , respectively, where the uncertainties represent the standard deviations of the daily averages. They also produce average ventilation rates of Q = 23.2 ± 0.4 L/s and Q = 21.7 ± 0.4 L/s, where the uncertainties are the standard deviations of the measurement errors. The results suggest that bio-based materials can perform as well as concrete thermal mass by optimizing their thickness and surface area to compensate for their inferior thermal mass properties. The results also suggest that the baseline temperature damping and ventilation rate of any naturally ventilated internal thermal mass can be accurately predicted using simplified ratios that scale with the number of occupants. These ratios are useful for early design or retrofit projects when primary materials are evaluated and selected, with the goal of improving thermal resilience while limiting lifecycle carbon emissions.

Investigation of window overhangs on natural cross ventilation in sheltered units of high-rise buildings in a moderately dense urban layout

In response to the increasing demand for energy-efficient housing in Tunisia, this study applies Design Builder simulations to investigate the effectiveness of passive and hybrid ventilation strategies in a representative dwelling situated in three distinct climate zones: temperate Mediterranean (Tabarka), Mediterranean (Sousse), and hot arid (Tozeur). The scenarios explored include optimized natural ventilation (based on window operation, scheduling, and opening temperature), phase change materials (PCMs), a solar chimney, reflective roofing, and a hybrid ventilation system, all evaluated against a conventional mechanical ventilation baseline. Results indicate that optimized natural ventilation is particularly effective, reducing annual energy consumption by 38.4–42.6 % and lowering CO₂ emissions by 6–10.8 %, depending on the region. While the hybrid ventilation system increased energy use by 14–16 %, it significantly improved thermal comfort, as reflected by enhanced PMV and PPD indices and by raising the proportion of comfortable occupied hours to nearly 76 %. Economically, optimized natural ventilation achieved the greatest savings, reaching 42.96 TD/m² in Tozeur, compared with 28.71 TD/m² for the hybrid approach. These findings highlight the substantial potential of climate-responsive passive and hybrid strategies to advance sustainable, cost-effective, and environmentally responsible residential buildings in Tunisia.

An enhanced multi-directional windcatcher with baffle-based design for high-performance natural ventilation in net zero energy buildings

CFD numerical setting combinations for greenhouse natural ventilation across diurnal time points using multi-criteria analysis

Asynchronous multi-agent reinforcement learning for coordinated control of natural ventilation and radiant cooling

Synchronizing the water, energy and food nexus in the Makran coastal region: A new approach using indigenous architectural patterns

Development of a natural ventilation windcatcher with fibrous pleated filter for severely polluted outdoor environment: numerical model development and systematical optimization

A Study and Development of Natural Ventilation Opening Design Guidelines for Single-Sided Residential Units to Improve Indoor Ventilation Quality in High-Rise Buildings in Chiang Mai

Public health response to a tuberculosis cluster in a high-rise apartment block.

The main problem in small houses located in dense urban areas is the lack of natural sunlight and poor air circulation caused by building density and limited openings, which reduces occupants’ thermal comfort. This study examines the combination of a ventilation chimney and cross ventilation as a passive strategy to improve indoor air quality and natural lighting in a single-story house. The research uses a qualitative-descriptive approach through the study of stack effect theory, natural convection, passive ventilation, and design analysis based on a case study of a residential house located at Jalan Caladi No. 52, Sadang Serang Subdistrict, Coblong District, Bandung City. A 7.70- meter-high ventilation chimney was designed to utilize the temperature difference between indoor and outdoor air in order to generate buoyancy-driven airflow (stack effect). This system is combined with cross ventilation through a corridor inside the building. Natural air movement ranging from 0.2-1.0 m/s can improve occupants’ thermal comfort and help reduce heat accumulation inside the space. The application of the ventilation chimney and cross ventilation in this design is theoretically capable of increasing natural air exchange and accelerating the release of hot air through the vertical shaft. The ventilation chimney also functions as a light well that helps distribute natural lighting into the surrounding spaces. The results of the study indicate that the combination of this passive ventilation strategies has the potential to improve air circulation quality, thermal comfort, and natural lighting in houses located in dense urban environments.