Search Results (29)

Human health risk assessment of vapor intrusion caused by organic pollutants is commonly based on steady-state predictions of partition and vapor migration in the subsoil. This study develops a pseudo-dynamic, process-based Partition–Diffusion Risk Model (PDRM) using a one-dimensional numerical model for organic mixtures to assess the time evolution of cancer and non-cancer risks, indoor air concentrations, and non-aqueous phase liquid (NAPL) formation. The model has been applied to a low-carbon sandy soil without microbial degradation, which might be a worst-case scenario. Six simulation scenarios combined two source concentrations (1000 and 3000 mg/kg) and three source depths (1, 3, and 5 m) over 30 years. Results show that source depth governs exposure dynamics: shallow contamination poses unacceptable risks rapidly but declines quickly, whereas at greater depths, unacceptable levels appear later and persist throughout the exposure period. NAPL formation may act as a secondary source, sustaining vapor release and extending indoor exposure under high-loading conditions. Multicomponent partitioning induces nonlinear, compound-specific behavior, with the first 3–5 years representing a critical period for rapid risk changes. Conventional models show that neglecting NAPL formation and time variability may lead to an underestimation of cancer risk by up to an order of magnitude. These findings highlight the importance of incorporating depth and time-dependent characterization to reduce uncertainty in vapor intrusion risk assessments. Full article

The effectiveness of mixing ventilation for contaminant removal and maintaining indoor air quality remains an active topic of debate. In shared multi-person spaces, it is common for occupants to experience uneven exposure levels due to variations in system configuration and seating arrangements. Previous studies have primarily considered static occupancy schemes, leaving a gap in understanding how dynamic patterns of use interact with ventilation design. This study investigates the combined effects of system settings and occupancy patterns on ventilation effectiveness (VE), while also exploring whether lower ventilation rates can still sustain acceptable air quality. Validated Computational Fluid Dynamics (CFD) models were developed to simulate multiple scenarios involving three ceiling heights, two inlet and exhaust configurations, and three occupancy patterns. Analysis of air quality at the breathing zone reveals that the spatial arrangement of ventilation inlets and exhausts substantially influences VE, with optimized layouts improved system effectiveness by approximately 20%. Seating arrangement was similarly important, with favorable positioning relative to inlets improving perceived air quality by up to 25%. In addition, modest increases in ceiling height reduced the ventilation rate needed to maintain equivalent air quality, suggesting opportunities for energy savings without compromising occupant health. Overall, this study demonstrates that the interaction between system configuration and occupancy has a stronger impact on ventilation performance. These findings underscore the importance of integrated design strategies that align ventilation layout with occupant distribution to achieve both efficiency and equity in indoor environments. Full article

Displacement ventilation systems can offer healthy indoor air quality (IAQ) by maintaining stratified flows that transport and expel airborne contaminants through the upper region of indoor spaces. Using large eddy simulation (LES), we investigate displacement ventilation in a generic indoor space under varying ventilation flow rates and supply–exhaust configurations. Assessing the ventilation system requires quantitative evaluation of airborne contaminants, for which CO₂ concentration is typically used as a proxy. However, in this study, we show that there is both a qualitative and quantitative correlation between CO₂ and airborne respiratory particles using computational particle fluid dynamics simulations. The role of the ventilation flow rate in ventilation efficacy is investigated for low values ranging from 0.01 to 0.06 m³/s, and the role of supply–exhaust configuration is assessed by considering in-line and staggered layouts. At low flow rates (0.01 to 0.04 m³/s), the ventilation system maintains a stable stratified layer within the room. Within this regime, the CO₂ level in the occupied zone is inversely proportional to the ventilation rate. At higher flow rates, the ventilation transitions to a mixing regime, effectively nullifying the intended design of the system. Interestingly, the two opening configurations produce nearly identical trends, suggesting that jet strength and room geometry dominate over modest opening shifts in this setup. Full article

The growing demands for sanitary regulations in medical facilities, particularly operating rooms, highlight the importance of ensuring high air quality and minimizing airborne hospital-acquired infections. Improperly designed ventilation systems may lead to contamination of up to 90–95% of patients, especially in light of evolving threats, such as COVID-19. This study focuses on enhancing the energy efficiency and performance of air conditioning and ventilation systems for cleanrooms, where air recirculation is not permissible. A novel energy-efficient direct-flow air treatment scheme is proposed, integrating a heat pump system with adjustable thermal output. A computational fluid dynamics CFD model of a clean operating room was developed to assess the impact of inlet air velocity on aerosol particle removal and airflow stabilization time. The model also considers the effect of personnel movement. The results supported optimized air distribution, reducing microbial contamination risks, with less than 10 CFU/m³, and improved thermal performance. The proposed system was evaluated for energy and cost efficiency compared to conventional setups. Findings can inform the design and operation of cleanroom ventilation in surgical environments and other high-tech applications. This research contributes to improving indoor air quality and reducing infection risks while enhancing sustainability in healthcare infrastructure. Full article

High-temperature and high-pollution mobile sources are frequently encountered in industrial environments. Fixed-position exhaust outlets often fail to promptly remove heat and contaminants when these sources are in motion, leading to local accumulation and reduced indoor air quality. This study proposes a novel mobile exhaust system capable of tracking and dynamically aligning with moving emission sources to improve heat removal and cooling efficiency. Three configurations were evaluated: (1) a fixed exhaust outlet, (2) an exhaust vent moving synchronously with the heat source, and (3) a buoyancy-driven tracking exhaust outlet. Small-scale experiments and CFD simulations using dynamic mesh techniques were conducted. The results showed that the synchronous system reduced ambient temperature by an average of 0.25 to 2.3 °C compared to the fixed outlet, while the buoyancy-tracking system achieved an additional 0.15 to 2.5 °C reduction. The study also introduces a correlation between thermal plume inclination and the Archimedes number, providing a predictive basis for exhaust positioning. Given the similar dispersion patterns of heat and airborne pollutants, the proposed system holds promise for both thermal management and contaminant control in dynamic industrial environments. Furthermore, the system may offer critical advantages in emergency ventilation scenarios involving intense heat or hazardous pollutant outbreaks. Full article

The indoor microbiome is a dynamic ecosystem including pathogens that can impact human health. In this regard, the school environment represents the main living space of humans for many years, and an unhealthy environment can significantly condition students’ health. School rooms can suffer from insufficient ventilation and the use of building materials that may favor pathogen contamination, mostly sanitized by conventional chemical-based methods, which can impact pollution, have temporary effects, and induce the selection of antimicrobial resistance (AMR) in persistent microbes. In the search for sustainable and effective methods to improve the healthiness of the classroom environment, a pre–post case–control study was performed in an Italian high school. Over a year, different interventions were sequentially placed and evaluated for their impact on bioburden and air quality, including the introduction of plants, a mechanical ventilation system, and probiotic-based sanitation (PBS) in substitution for chemical sanitation. Through continuous microbial monitoring of the enrolled school rooms, via culture-dependent and -independent methods, a remarkable bioburden level was detected at baseline (around 12,000 and 20,000 CFU/m², before and after classes, respectively), composed mostly of Staphylococcus spp. and fungi. Some decrease in fungal contamination was observed following the introduction of plants. Still, the most significant decrease in pathogens and associated AMR was detected following the introduction of ventilation and PBS, which decreased pathogen level by >80% (p < 0.001) and AMR by up to 3 Log₁₀ (p < 0.001) compared to controls. Collected data support the use of combined strategies to improve indoor microbial quality and confirm that PBS can effectively control bioburden and AMR spread not only in sanitary environments. Full article

Human health is significantly impacted by the quality of the air in living areas. Numerous factors, such as the kind of particle, clean air delivery rate, room geometry, surface features, and thermal plume produced by people or other equipment, all have an impact on indoor particle movement. This work uses computational fluid dynamics to quantitatively examine the performance of a portable air purifier that is routinely used to improve the indoor air quality of a room. The volumetric flow rate, particle diameter, and placement of the air cleaner device were considered in the assessment of the particle transport characteristics. The temperature, velocity, and age of the air distribution in the room were computed in three-dimensional simulations, and the effectiveness of the air cleaning device (ACD) in eliminating contaminants was then investigated. Clean air delivery rate (CADR), collection efficiency, and particle concentration rate values were also computed for every case that was taken into consideration. It is found that CADR and collection efficiency values for larger particles are about 2–7% better than those for smaller particles. The collection efficiency of ACD with different operating conditions is in the range of 71% to 87%. Better collection performance parameters are observed with higher flow rates. Full article

In the aftermath of the COVID-19 pandemic, the urgent need for the rapid deployment of healthcare facilities propelled the rise of modular construction using an infill approach. In these modular, negative-pressure wards, the design of indoor airflow and pressure plays a crucial role in meeting the ventilation strategies required for isolation facilities. Accordingly, this paper focuses on modular negative-pressure wards employing an infill construction method and proposes an appropriate spatial pressure distribution to address the problem of air tightness degradation due to leakage. This study analyzed the indoor airflow and pressure distribution of a unit module corresponding to an infill. It aimed to examine whether the pressure difference with the adjacent room is maintained and to assess its effectiveness in isolating contaminated air. First, the airflow rate of the heating, ventilation, and air conditioning system in the unit module was calculated to ensure that it would meet the performance criteria of the negative-pressure ward. Afterward, based on the calculated rate, the study assessed the airflow and room-specific pressure within a typical floor, encompassing both the unit module and associated nursing support facilities. Here, the airflow in the external corridor of the typical floor was divided into two cases according to the pressure distribution: negative pressure and atmospheric pressure. The calculation results were compared using a computational fluid dynamics tool. The analysis results confirm that the air isolation performance is adequate as the pressure difference between adjacent rooms in the unit module and the typical floor was maintained at 2.5 Pa. Additionally, the indoor airflow in the negative-pressure isolation room formed a stable flow at a slow speed of 0.1–0.2 m/s, minimizing the possibility of air contamination from outside the isolation room. In particular, Case B of the typical floor design proposes a method to optimize the pressure distribution in the modular negative-pressure ward by designing the ventilation flow rate at atmospheric pressure level. Thus, this study emphasizes that atmospheric pressure design is appropriate when designing pressure in areas where negative-pressure control is difficult and can contribute to the design and improvement of similar medical facilities in the future. Full article

The escalating utilization of pesticides has led to pronounced environmental contamination, posing a significant threat to agroecosystems. The extensive and persistent global application of these chemicals has been linked to a spectrum of acute and chronic human health concerns. This review paper focuses on the concentrations of airborne pesticides in both indoor and outdoor environments. The collection of diverse pesticide compounds from the atmosphere is examined, with a particular emphasis on active and passive air sampling techniques. Furthermore, a critical evaluation is conducted on the methodologies employed for the extraction and subsequent quantification of airborne pesticides. This analysis takes into consideration the complexities involved in ensuring accurate measurements, highlighting the advancements and limitations of current practices. By synthesizing these aspects, this review aims to foster a more comprehensive and informed comprehension of the intricate dynamics related to the presence and measurement of airborne pesticides. This, in turn, is poised to significantly contribute to the refinement of environmental monitoring strategies and the augmentation of precise risk assessments. Full article

Due to rising energy costs, there is a trend to return to conventional heating systems powered by solid fuel. A rise in the combination of new and old energy sources is creating unintended dual-fuel heating systems. These systems combine an old solid-fuel furnace and a new gas furnace. Usually, the old furnace was meant to be replaced by the new one and their cooperation was never intended when installing the new heating system. The occupants decided to leave the old system in fear of a rise in prices of gas or electricity or temporary problems with their supply. The study focuses on such a system and its influence on indoor air quality and thermal comfort. A series of dynamic measurements with an IoT remote sensor array in a chosen household was conducted to evaluate the behaviour of the system as well as effects on the indoor environment. Sensors measured the CO₂ concentration and thermal profile in a household when using a dual-fuel heating system consisting of an old wood furnace from the 1980s and a recently installed new gas furnace. The results showed that none of the heat sources posed a threat to the occupants. Contaminants were safely removed by the exhaust systems of the furnaces. The thermal comfort, however, was influenced more by the wood furnace where fluctuations in the temperature were noticed, especially during the night. The gas furnace maintained a stable temperature that was more suitable for the occupants. Full article

Infection containment in the post-pandemic scenario became a top priority for healthcare engineering control staffers, especially in pneumology sectors, where the treatment of airborne infectious diseases is frequent. In Brazil, where COVID-19 left a long record of casualties, there is a lack of information on the influence of filtration systems on the maintenance of regulated operational conditions for indoor comfort in hospital environments. This paper has the following objectives: to study arrangements of filtering systems in hospital acclimatization ducts; to verify how filtering characteristics could compromise safety regulations for airflow in hospital environments; and to identify airflow stagnation points that might favor suspended viral concentrations and increase contamination risks. We used the computational fluid dynamics STAR-CCM+© software to perform numerical simulations of different cases of indoor airflow in a model corresponding to a sector of the Lauro Wanderley University Hospital (João Pessoa city, Brazil). We concluded that standards for maximum velocity are reachable despite thinner or thicker filters affecting the spread of the air. In this way, acclimatization systems are limited by a tradeoff between regulation and protection. Our findings are relevant to future technological development, interventions, safety strategies amidst contamination scenarios, and new filtration arrangements in hospital environments. Full article

Existing indoor closed ultraviolet-C (UVC) air purifiers (UVC in a box) have faced technological challenges during the COVID-19 breakout, owing to demands of low energy consumption, high flow rates, and high kill rates at the same time. A new conceptual design of a novel UVC-LED (light-emitting diode) air purifier for a low-cost solution to mitigate airborne diseases is proposed. The concept focuses on performance and robustness. It contains a dust-filter assembly, an innovative UVC chamber, and a fan. The low-cost dust filter aims to suppress dust accumulation in the UVC chamber to ensure durability and is conceptually shown to be easily replaced while mitigating any possible contamination. The chamber includes novel turbulence-generating grids and a novel LED arrangement. The turbulent generator promotes air mixing, while the LEDs inactivate the pathogens at a high flow rate and sufficient kill rate. The conceptual design is portable and can fit into ventilation ducts. Computational fluid dynamics and UVC ray methods were used for analysis. The design produces a kill rate above 97% for COVID and tuberculosis and above 92% for influenza A at a flow rate of 100 L/s and power consumption of less than 300 W. An analysis of the dust-filter performance yields the irradiation and flow fields. Full article

Methamphetamine manufacture, use, and the resulting contamination is a significant issue that affects public health, the environment, and the economy. Third-hand exposure to methamphetamine can result in adverse health risks for individuals and first responders. Such exposures can result from the inhalation of airborne residues or from contact with contaminated objects. This review was conducted to determine the current methods used for methamphetamine extraction from indoor air and porous fabric materials. Dynamic solid phase microextraction (SPME) and sorbent sampling tubes have been applied to extract airborne methamphetamine residues from contaminated properties. SPME and solvent extraction have been applied to sample clothing and textiles for methamphetamine detection. This review demonstrates that there is limited literature on the detection of methamphetamine from indoor air and clothing. Supplementary and consistent methods to detect methamphetamine from air and porous surfaces should be developed and published to allow better assessment of the environmental risk to public health caused by third-hand exposure to methamphetamine. Full article

The supply of fresh air for underground rail transit systems is not as simple as opening windows, which is a conventional ventilation (CV) measure adopted in aboveground vehicles. This study aims to improve contaminant dilution and air purification in subway car ventilation systems and the safety of rail transit post-coronavirus disease pandemic era. We designed an air conditioning (AC) terminal system combined with stratum ventilation (SV) to enable energy consumption reduction for subway cars. We experimentally tested the effectiveness of a turbulence model to investigate ventilation in subway cars. Further, we compared the velocity fields of CV and SV in subway cars to understand the differences in their airflow organizations and contaminant removal efficiencies, along with the energy savings of four ventilation scenarios, based on the calculations carried out using computational fluid dynamics. At a ventilation flow rate of 7200 m³/h, the CO₂ concentration and temperature in the breathing areas of seated passengers were better in the SV than in the CV at a rate of 8500 m³/h. Additionally, the energy-saving rate of SV with AC cooling was 14.05%. The study provides new ideas for reducing the energy consumption of rail transit and broadens indoor application scenarios of SV technology. Full article

The quality of indoor air in healthcare facilities, with an emphasis on dental offices, attracted the attention of the scientific community in the late 1960s. Since then, it has become evident that the indoor air quality is critical in modern dental care facilities for limiting the spread of airborne infections, including vaccine-preventable diseases, and a key component of safety for healthcare personnel and patients. In the past decades, the role of indoor air quality has also been recognized in non-healthcare facilities, given the increasing time spent indoors by humans. During the provision of dental care services, mainly in the field of restorative dentistry, high-speed dental handpieces emitting air and water are used, producing large quantities of aerosol and hovering inside the operations area. In modern dental offices, new devices emitting air/powder for cavities improvement and cleaning as well as for periodontal prophylactic cleaning and aesthetics are used. In addition, a new therapeutic protocol for the removal of bacterial biofilm, targeting treatment for peri-implant diseases and conditions using air-abrasive decontamination technology, has been introduced in daily dental practice. The aim of this non-systemic review is to present the current state of knowledge on the nature and dynamics of air splatters and to provide an update to management and control strategies in dental care facilities, focusing on air purification and ultraviolet devices proposed and used. The findings arising from the limited number of related published articles documenting the reduction in levels of particular matter 2.5 (PM_2.5), PM₁₀ and volatile organic compounds, allow us to conclude that the continuous operation of air purifiers during and after treatment, contributes considerably to the improvement of the indoor air quality in dental care facilities. Moreover, the utilization of air purifiers is highly recommended in dental practice to mitigate spread of infections, including vaccine-preventable diseases. Frequent cleaning and maintenance of the purifier sieves and filters and frequent renovation of the indoor air through physical ventilation by mean of open windows is imperative. More research on environmental contamination and particularly on viral contamination under real dental care conditions is needed. Full article