Search Results (38)

This study investigates the seasonal effectiveness of high-efficiency particulate air (HEPA) purifiers and window-opening behaviors in three London nurseries, using continuous indoor and outdoor PM_2.5 monitoring, window state and air purifier use, and occupant questionnaire data collected from March 2021 to February 2022. Of the approximately 40–50 nurseries contacted, only three agreed to participate. Results show that HEPA purifiers substantially reduced indoor particulate matter (PM_2.5), with the greatest effect observed during the heating season when windows remained closed for longer periods. Seasonal and behavioral analysis indicated more frequent and longer window opening in the non-heating season (windows were open 41.5% of the time on average, compared to 34.2% during the heating season) driven by both ventilation needs and heightened COVID-19 concerns. Predictive modeling identified indoor temperature as the main driver of window opening, while carbon dioxide (CO₂) had a limited effect. In addition, window opening often increased indoor PM_2.5 under prevailing outdoor air quality conditions, with mean concentrations rising from 2.73 µg/m³ (closed) to 3.45 µg/m³ (open), thus reducing the apparent benefit of air purifiers. These findings underscore the complex interplay between mechanical purification and occupant-controlled ventilation, highlighting the need to adapt indoor air quality (IAQ) strategies to both seasonal and behavioral factors in educational settings. Full article

Tobacco smoking and electronic cigarette (EC) use are associated with elevated levels of particulate matter (PM) and nicotine in indoor environments. This study assessed filtration and nicotine capture efficiency of untreated and citric acid-treated high efficiency particulate air (HEPA) filters from two manufacturers, “on-brand” (original) and “off-brand” (replacement). When challenged with salt aerosol, the filtration efficiency (FE) (Mean ± RSD) of original HEPA filters (99.9% ± 0.1) was significantly higher than replacements (94.4% ± 1.7), but both were significantly below the HEPA designation of 99.97%. No significant differences in FE were observed between treated and untreated HEPA filters. All filters had lower FE for EC aerosol compared to salt aerosol, especially among replacement filters. Nicotine capture efficiency was significantly higher in citric acid-treated HEPA filters for originals (99.4% ± 0.22) and replacements (99.0% ± 1.07) compared to untreated originals (57.4% ± 2.33) and replacements (42.0% ± 14.20). This study demonstrated that our citric acid treatment of HEPA filters was effective and efficient at capturing airborne nicotine and did not affect the FE for PM. Use of citric acid-treated HEPA filters would be an effective exposure reduction strategy for both nicotine and PM in indoor settings. Full article

This study assesses indoor air quality (IAQ) in two schools in the Democratic Republic of Congo (DRC), contributing scientific data for a developing tropic such as the DRC marked by the absence of sufficient study on the indoor environmental quality (IEQ) in school buildings. Over ten weeks, we monitored IEQ parameters in two schools, considering their unique geographical and environmental settings. Using a calibrated IEQ multiprobe and particle counters, we measured the CO₂ levels, temperature, relative humidity, and particulate matter (PM). Our data analysis, which included ANOVA and correlation assessments, revealed a concerning trend. We found that the CO₂ and PM concentrations in the classroom were significantly high, often exceeding recommended safety thresholds. The current natural ventilation systems were found to be inadequate, particularly in managing CO₂ concentrations and PM levels influenced by proximity to industrial activities. Our study recommends that schools in similar settings adopt mechanical ventilation systems with high-efficiency particulate air (HEPA) filters to improve IAQ. We also recommend regular monitoring and dynamic air quality adjustment based on real-time data to ensure the effectiveness of implemented interventions. Furthermore, we propose that future studies focus on a broader range of environmental conditions and include many schools and educational buildings to enhance the generalisability of the findings. Long-term health outcomes and the cost-effectiveness of different ventilation strategies should also be explored to develop adapted, sustainable interventions for improving student well-being and performance in schools globally. Full article

High-efficiency particulate air (HEPA) filter purifiers are a recommended method for eliminating respiratory airborne droplets. In this study, the movement of airborne droplets exhaled by occupants in an unventilated, two-bed dormitory room with an air purifier was simulated using computational fluid dynamics. The air was modeled using an Eulerian scheme while the droplets were modeled using a Lagrangian method. The airborne droplet number, the rate at which droplets are removed, and the rate at which droplets accumulate were calculated. A larger HEPA flow rate increased the droplet removal efficiency, with most of the droplets settling on boundary surfaces. Of particular note, the air purifier location within the room had a significant impact on reducing the droplet exchange between two occupants and improving the droplet elimination efficiency. Full article

High-Efficiency Particulate Air (HEPA) filtration plays a crucial role in maintaining air quality in critical environments such as lean rooms, hospitals, and nuclear facilities. The point of this study is to look into how well nuclear-grade HEPA filters work and behave by looking at the main ways they catch particles using two modeling methods to figure out how well the filters work overall. This study encompasses particles with diameters ranging from 0.05 to 5.00 µm and a density of 1500 kg/m³. The current study systematically examined key parameters such as particle size, fiber diameter, and filtration velocity, which revealed their significant influence on the HEPA filter efficiency. Notably, the most penetrating particle size (MPPS) is identified within the expected range of 0.1–0.3 µm for both approaches. A critical threshold in fiber diameter is discovered when it exceeds 0.85 µm, resulting in a substantial shift in particle penetration and overall collection efficiency. This study also explored the impact of filtration velocity on filter performance, demonstrating increasing deviations as velocity rises, following a polynomial trend. The current study also rigorously validated the model predictions against experimental data from uranine particle filtration tests, confirming the model’s accuracy and applicability. These findings provide essential insights for optimizing the design and operation of nuclear HEPA filters, emphasizing the necessity of considering the particle size, fiber diameter, and filtration velocity. Both modeling approaches exhibit a negligible 0.04% deviation in the MPPS efficiency, which increases polynomially with the filtration velocity. Importantly, both approaches consistently identified the same MPPS regardless of the filtration velocity. Additionally, the model reinforces the substantial impact of fiber size on filter efficiency. A comprehensive comparison with the experimental data yielded closely aligned results with a maximum deviation of 1.14%. This validation strengthens the model’s ability to elucidate the underlying physical phenomena governing the influence of filtration velocity on efficiency, making it a valuable tool in nuclear HEPA filter research and development. Full article

The establishment of a compliant radiopharmacy facility within a university setting is crucial for supporting fundamental and preclinical studies, as well as for the production of high-quality radiopharmaceuticals for clinical testing in human protocols as part of Investigational New Drug (IND) applications that are reviewed and approved by the U.S. Food and Drug Administration (FDA). This manuscript details the design and construction of a 550 ft² facility, which included a radiopharmacy and a radiochemistry laboratory, to support radiopharmaceutical development research and facilitate translational research projects. The facility was designed to meet FDA guidelines for the production of aseptic radiopharmaceuticals in accordance with current good manufacturing practice (cGMP). A modular hard-panel cleanroom was constructed to meet manufacturing classifications set by the International Organization of Standardization (ISO), complete with a gowning room and an anteroom. Two lead-shielded hot cells and two dual-mini hot cells, connected via underground trenches containing shielded conduits, were installed to optimize radioactive material transfer while minimizing personnel radiation exposure. Concrete blocks and lead bricks provided sufficient and cost-effective radiation shielding for the trenches. Air quality was controlled using pre-filters and high-efficiency particulate air (HEPA) filters to meet cleanroom ISO7 (Class 10,000) standards. A laminar-flow biosafety cabinet was installed in the cleanroom for preparation of sterile dose vials. Noteworthy was a laminar-flow insert in the hot cell that provided a shielded laminar-flow sterile environment meeting ISO5 (class 100) standards. The design included the constant control and monitoring of differential air pressures across the cleanroom, anteroom, gowning room, and controlled research space, as well as maintenance of temperature and humidity. The facility was equipped with state-of-the-art equipment for quality control and release testing of radiopharmaceuticals. Administrative controls and standard operating procedures (SOPs) were established to ensure compliance with manufacturing standards and regulatory requirements. Overall, the design and construction of this radiopharmacy facility exemplified a commitment to advancing fundamental, translational, and clinical applications of radiopharmaceutical research within an academic environment. Full article

Previous research has indicated that ultrafine particles (UFPs, particles less than 100 nm) emitted from desktop three-dimensional (3D) printers exhibit cytotoxicity. However, only a limited number of particles from different filaments and their combinations have been tested for cytotoxicity. This study quantified the emissions of UFPs from a commercially available filament extrusion desktop 3D printer using three different filaments, including acrylonitrile butadiene Styrene (ABS), thermoplastic polyurethane (TPU), and polyethylene terephthalate glycol (PETG). In this study, controlled experiments were conducted where the particles emitted were used to expose cells grown in an air-liquid interface (ALI) system. The ALI exposures were utilized for in vitro characterization of particle mixtures, including UFPs from a 3D printer. Additionally, a lactate dehydrogenase (LDH) assay was used to evaluate the cytotoxic effects of these UFPs. A549 cells were exposed at the ALI to UFPs generated by an operational 3D printer for an average of 45 and 90 min. Twenty-four hours post-exposure, the cells were analyzed for percent cytotoxicity in a 24-well ALI insert (LDH assay). UFP exposure resulted in diminished cell viability, as evidenced by significantly increased LDH levels. The findings demonstrate that ABS has the most significant particle emission. ABS was the only filament that showed a significant difference compared to the high efficiency particulate arrestance (HEPA) following 90 min of exposure (p-value < 0.05). Both ABS and PETG exhibited a significant difference compared to the HEPA control after 45 min of exposure. A preliminary analysis of potential exposure to these products in a typical environment advises caution when operating multiple printer and filament combinations in poorly ventilated spaces or without combined gas and particle filtration systems. Full article

In the midst of the COVID-19 pandemic, new requirements for clean air supply are introduced for heating, ventilation, and air conditioning (HVAC) systems. One way for HVAC systems to efficiently remove airborne viruses is by filtering them. Unlike disposable filters that require repeated purchases of consumables, the electrostatic precipitator (ESP) is an alternative option without the drawback of reduced dust collection efficiency in high-efficiency particulate air (HEPA) filters due to dust buildup. The majority of viruses have a diameter ranging from 0.1 μm to 5 μm. This study proposed a two-stage ESP, which charged airborne viruses and particles via positive electrode ionization wire and collected them on a collecting plate with high voltage. Numerical simulations were conducted and revealed a continuous decrease in collection efficiencies between 0.1 μm and 0.5 μm, followed by a consistent increase from 0.5 μm to 1 μm. For particles larger than 1 μm, collection efficiencies exceeding 90% were easily achieved with the equipment used in this study. Previous studies have demonstrated that the collection efficiency of suspended particles is influenced by both the ESP voltage and turbulent flow at this stage. To improve the collection efficiency of aerosols ranging from 0.1 μm to 1 μm, this study used a multi-objective genetic algorithm (MOGA) in combination with numerical simulations to obtain the optimal parameter combination of ionization voltage and flow speed. The particle collection performance of the ESP was examined under the Japan Electrical Manufacturers’ Association (JEMA) standards and showed consistent collection performance throughout the experiment. Moreover, after its design was optimized, the precipitator collected aerosols ranging from 0.1 μm to 3 μm, demonstrating an efficiency of over 95%. With such high collection efficiency, the proposed ESP can effectively filter airborne particles as efficiently as an N95 respirator, eliminating the need to wear a mask in a building and preventing the spread of droplet infectious diseases such as COVID-19 (0.08 μm–0.16 μm). Full article

Particulate matter air pollution and volatile organic compounds released into the air from the incomplete combustion of fossil fuels and wildfires creates significant damage to human health and the environment. Advances in air filtration and purification technology are needed to mitigate aerosol hazards. This article details an effort to explore the potential benefits of new materials and methods for the production of nonwoven air filtration media through electrospinning and stabilizing polyacrylonitrile fibers. The investigated production methods include electrospinning fibrous matting onto a stainless steel wire mesh and stabilizing the nonwoven media in a chamber furnace. The media is then tested for air filtration penetration and airflow resistance, and the fiber size distribution is measured using scanning electron microscopy. The experimental results show that the electrospun media approaches the performance criteria for airflow resistance and particle capture efficiency of high-efficiency particulate air (HEPA) filter media. Furthermore, performance estimations for electrospun media of increased thickness and for a decreased filtration velocity show potential to exceed the HEPA media resistance and efficiency criteria. Thus, it is suggested that electrospun and stabilized nonwoven fibrous media are candidates as alternatives to traditionally manufactured HEPA media and may potentially benefit modern air filtration technology and reduce hazards associated with particulate matter. Additionally, the authors recommend future exploration into the carbonization and activation of electrospun filter media for the adsorption and mitigation of volatile organic compounds as a secondary benefit, while maintaining high efficiency and low airflow resistance in the removal of particulate matter from aerosol streams. Full article

Bacterial infections are a major concern as antibiotic resistance poses a great threat, therefore leading to a race against time into finding new drugs or improving the existing resources. Nanomaterials with high surface area and bactericidal properties are the most promising ones that help combating microbial infections. In our case, graphene decorated with silver nanoparticles Gr-Ag (5 wt% Ag) exhibited inhibitory capacity against S. aureus and E. coli. The newly formed hybrid material was next incubated with high-efficiency particulate air (HEPA) filter, to obtain one with bactericidal properties. The modified filter had greater inhibitory action against the tested strains, compared to the control, and the effect was better against the Gram-negative model. Even if the bacteria remained attached to the filters, their colony forming unit capacity was affected by the Gr-Ag (5 wt% Ag) hybrid material, when they were subsequently re-cultured on fresh agar media. Therefore, the HEPA filter modified with Gr-Ag (5 wt% Ag) has high antibacterial properties that may substantially improve the existing technology. Full article

The Healthy Air, Healthy Schools Study was established to better understand the impact of ultrafine particles (UFPs) on indoor air quality in communities surrounding Seattle-Tacoma (Sea-Tac) International Airport. The study team took multipollutant measurements of indoor and outdoor air pollution at five participating school locations to estimate infiltration indoors. The schools participating in this project were located within a 7-mile radius of Sea-Tac International Airport and within 0.5 mile of an active flight path. Based on experimental measures in an unoccupied classroom, infiltration rates of (a) UFPs of aircraft origin, (b) UFPs of traffic origin, and (c) wildfire smoke or other outdoor pollutants were characterized before and after the introduction of a portable high-efficiency particulate air (HEPA) filter intervention. The portable HEPA cleaners were an effective short-term intervention to improve the air quality in classroom environments, reducing the UFP count concentration from one-half to approximately one-tenth of that measured outside. This study is unique in focusing on UFPs in schools and demonstrating that UFPs measured in classroom spaces are primarily of outdoor origin. Although existing research suggests that reducing particulate matter in homes can significantly improve asthma outcomes, further investigation is necessary to establish the benefits to student health and academic performance of reducing UFP exposures in schools. Full article

High-efficiency particulate air (HEPA) filters is a potential tool used to remove fine particles and improve indoor air quality. This study aims to analyze the real-world efficacy of portable HEPA air cleaners in a household environment. Laser light dispersion PM_2.5 sensors are used to continuously monitor the indoor and outdoor PM_2.5 level before and after HEPA air cleaner filtration. Overall, HEPA air cleaners significantly reduce the indoor PM_2.5 level (33.5 ± 10.3 vs. 17.2 ± 10.7 µg/m³, mean difference (MD) = −16.3 µg/m³, p < 0.001) and indoor/outdoor PM_2.5% (76.3 ± 16.8 vs. 38.6 ± 19.8%, MD = −37.7%, p < 0.001). The efficacy to reduce PM_2.5 is strongest in three machines with medium-flow setting group (indoor PM_2.5 MD: −26.5 µg/m³, indoor/outdoor PM_2.5 percentage MD: −56.4%). Multiple linear regression demonstrates that outdoor PM_2.5, machine number, airflow speed, and window ventilation are significant factors associated with indoor PM_2.5 concentrations (R = 0.879) and percentage of the indoor/outdoor PM_2.5 ratio (R = 0.808). HEPA air cleaners can effectively improve indoor PM_2.5 air pollution. Adequate air cleaner machine numbers, appropriate airflow, and window ventilation limitations are important to achieve the best efficacy of the HEPA air cleaner. Full article

Air purifiers should pay much attention to hospital-associated infections, but the role of a single air purifier is limited. The goal of this study was to evaluate the effectiveness of the combined application of the nonequilibrium positive and negative oxygen ion purifier (PNOI) and the high-efficiency particulate air filter (HEPA) on a complex, polluted environment. Two of the better performing purifiers were selected before the study. The efficacy of their use alone and in combination for purification of cigarette particulate matter (PM), Staphylococcus albicans, and influenza virus were then evaluated under a simulated contaminated ward. PNAI and HEPA alone are deficient. However, when they were combined, they achieved 98.44%, 99.75%, and 100% 30 min purification rates for cigarette PM, S. albus, and influenza virus, respectively. The purification of pollution of various particle sizes and positions was optimized and reduced differentials, and a subset of airborne influenza viruses is inactivated. Furthermore, they were superior to ultraviolet disinfection for microbial purification in air. This work demonstrates the strong purification capability of the combined application of these two air purifiers for complex air pollution, which provides a new idea for infection control in medical institutions. Full article

This study aimed to assess whether protective measures could reduce the health risks of air pollution in mice living in the chambers situated at a suburban site in Beijing. The living chambers of mice were divided into four groups: male mice with and without the high-efficiency particulate air (HEPA) filter (male group A and group B), as well as female mice with and without the HEPA filter (female group A and group B). The experiment was carried out from 1 December 2017 to 31 May 2018. Parameters of respiratory function during periods of clean air and air pollution were determined for all groups to evaluate the role of the indoor air filter (i.e., HEPA) in protection against respiratory health risks in mice. Significant differences in minute volumes were observed in male and female groups with versus without the HEPA. Additionally, respiratory health parameters including respiratory rate, duration of breaking, expiratory time, and relaxation time exhibited differences in female groups with HEPA versus without HEPA. Levels of inflammatory factors in the lungs were measured for all groups after 6months of exposure. Greater mean levels of IL-6 and TNF-α were found in the male groups without HEPA than in those with HEPA. Higher average concentrations of IL-6, T-AOC, SOD, GSH-Px, LDH, TNF-α, and TGF-β1 were found in the female group without HEPA than those without HEPA. Our study has proved the effective protection provided by indoor air filters (i.e., HEPA filters) in reducing respiratory health risks associated with PM_2.5. Full article

We performed a screening evaluation of the human health risk posed by nanocarbon materials at the lifecycle stages of manufacturing and the use of the solid carbon generated in hydrogen manufacture by methane decomposition. We first estimated the atmospheric emission volumes of the solid carbon produced by small-, medium-, and large-scale hydrogen manufacturing plants. We then estimated the atmospheric emission due to tire wear, which largely contributes to the emission of solid carbon usage. Next, we estimated the atmospheric concentration of solid carbon in an atmospheric simulation using the METI–LIS model, which estimates the atmospheric distribution of a pollutant’s concentration near methane decomposition factories. We also used the AIST–ADMER model that estimated the regional atmospheric distributions around central Tokyo, where the traffic volume is the highest nationally. Finally, we performed a screening evaluation of human health risk in the surrounding areas, considering the permissible exposure concentrations of solid carbon. Our study identified no risk concerns at small- and medium-scale factory locations equipped with high-efficiency particulate air (HEPA) filtration facilities. At large-scale factories installed with HEPA filters, these emissions likely remain within the factory site. Furthermore, we determined that emissions from tire wear pose no risk to human health. The surroundings of small- and medium-scale factory sites installed with HEPA filters posed no risk to human health. Full article