Search Results (127)

The rapid removal of fine contaminant particles (0.1–5 µm), including bioaerosols, from indoor air remains a critical challenge, particularly in emergency scenarios such as industrial accidents or biological incidents. This study develops a novel mathematical model that integrates the kinetic evolution of an impulse-sprayed powder aerosol (as an example, TiO₂, particle size 5–10 µm) with contaminant-capture efficiency, accounting for Brownian diffusion, inertial impaction, interception, and electrostatic attraction. The model incorporates the triboelectric charge acquired by sorbent particles during pneumatic spraying. Parametric calculations demonstrate that for uncharged particles, capture efficiency in the Greenfield gap is low (η = 0.1–0.3). However, when sorbent particles carry an opposite charge to the contaminants, the efficiency increases to over 0.7, and the characteristic capture time becomes substantially shorter than the gravitational settling time. A model-based criterion for sorption completeness is derived, indicating that, under the specified assumptions, sorbent particles with diameters of 5–7 µm satisfy the criterion at concentrations of approximately 1–2 g/m³. The model provides a theoretical and parametric framework for estimating the required sorbent concentration, capture efficiency, and characteristic purification time under specified room and particle conditions. The results can support the preliminary design of rapidly deployable emergency air-cleaning systems. Full article

Airborne viral transmission necessitates effective indoor air purification strategies. Conventional methods often face operational challenges, including potential secondary aerosolization and performance degradation under high-humidity conditions. This study evaluates a hybrid control system integrating a multi-walled carbon nanotube (MWCNT) field-emission plasma with a UV-LED/TiO₂ photocatalyst to continuously inactivate airborne bacteriophages. The system’s performance was assessed under varying applied voltages and relative humidity (RH) levels. The kinetic results demonstrated that the hybrid configuration yields a synergistic inactivation effect compared to the isolated plasma or photocatalytic treatments. Based on the kinetic enhancement, it is hypothesized that trace ozone generated by the plasma discharge serves as an electron acceptor on the UV-illuminated TiO₂ surface, thereby mitigating electron–hole recombination and enhancing the generation of hydroxyl radicals (·OH). Furthermore, the hybrid system exhibited operational resilience under high-moisture conditions, maintaining a robust active inactivation constant (k_a = 0.190 min⁻¹) at 70% RH without statistical degradation. This stability indicates that the continuous field emission effectively utilizes ambient moisture for secondary radical generation rather than being quenched by water condensation. Ultimately, this hybrid technology presents a continuous and adaptable engineering control measure for mitigating airborne pathogens in enclosed occupational environments, including those in high-humidity climates. Full article

Vertical greenery is increasingly applied in modern cities for environmental improvement and landscape enhancement. Given the insufficient coverage of recent developments in research and practice by prior reviews, this paper conducts a systematic review based on literature from Web of Science and global patent databases following PRISMA guidelines, with CiteSpace used for bibliometric analysis. This study summarizes the theoretical achievements of vertical greenery in ecological environment, building energy efficiency and technical materials. It also analyzes practical innovations via patent mining—a new supplement compared with traditional reviews. The environmental impacts of both outdoor and indoor vertical greenery are elaborated on: outdoor systems improve urban microclimate, noise control and air quality; indoor systems enhance indoor comfort, air purification and people’s mental status. Current innovations are categorized into structure and equipment, intelligent management, and social–cultural values. The outcomes of this work offer practical guidance for the design, construction and maintenance of vertical greenery in real projects. This paper also identifies future research priorities for the long-term development of vertical greenery. Full article

Formaldehyde (HCHO), a prevalent indoor air pollutant released from furniture and building materials, poses significant health risks due to its carcinogenic nature. In this study, a binary cuprous oxide–titanium dioxide (Cu₂O–TiO₂) composite photocatalyst was synthesized via a hydrothermal method to enable efficient visible-light-driven degradation of gaseous formaldehyde at ambient temperature. The structural, morphological, and optical properties of the as-prepared catalysts were characterized using XRD, SEM, TEM, EDX, and UV-Vis spectroscopy. While pristine Cu₂O exhibited a formaldehyde degradation efficiency of approximately 68% under white light illumination, the incorporation of TiO₂ markedly enhanced the photocatalytic performance. Among the different mass ratios tested, the Cu₂O–TiO₂ (1:1) composite demonstrated the highest activity, achieving 83% degradation of formaldehyde within 240 min under white light. Enhanced performance is attributed to the formation of a heterojunction that reduces the effective bandgap, promotes charge separation, and suppresses electron–hole recombination. Additionally, the generation of carbon dioxide and water as end products confirmed complete mineralization. The catalyst also showed good reusability, retaining over 81% efficiency after five cycles. This work presents a cost-effective, stable, and visible-light-active Cu₂O–TiO₂ heterojunction photocatalyst with strong potential for indoor air purification applications. Full article

This study investigates the simultaneous elimination of ethyl acetate (EA), a representative volatile organic compound (VOC), and Escherichia coli aerosols from indoor air using a continuous-flow dielectric barrier discharge (DBD) plasma reactor coupled with a photocatalytic luminous textile system (Cu/TiO₂-coated fibers). The effects of applied voltage, relative humidity, and air-flow rate on pollutant removal and disinfection performance were systematically evaluated. Optimal DBD operation at 18 kV, 1 m³ h⁻¹ airflow, and 70% relative humidity achieved single-process removal efficiencies of 77% for EA and 2 log reduction (CFU mL⁻¹) for E. coli. When photocatalysis was coupled with DBD plasma, a significant combined effect was observed, increasing EA degradation to 87% and bacterial inactivation to 3.8 log (CFU mL⁻¹). The coupling enhanced active-species generation, improved CO₂ selectivity (up to 53%), and reduced residual ozone concentration. Humidity positively affected microbial inactivation due to °OH radical formation but slightly decreased VOC degradation by limiting ozone regeneration. Results demonstrate the efficiency and scalability of the DBD–photocatalysis hybrid system for multi-pollutant indoor air purification, offering rapid, low-temperature treatment suitable for industrial-scale applications. Full article

In megacities, where conventional mitigation strategies exhibit variable and environment-dependent performance, urban air pollution continues to be a significant public health concern. To methodically assess the operational reliability of urban smog mitigation systems under dynamic atmospheric conditions, this study proposes a data-driven failure analysis approach. A machine learning architecture based on Random Forest and XGBoost algorithms is developed using integrated meteorological and air quality metrics from Lahore, Pakistan, such as temperature, wind speed, and relative humidity. AQI is used as an integrated pollution indicator alongside meteorological variables to enhance the model’s ability to capture overall atmospheric pollution impact and improve the accuracy of smog mitigation failure prediction. This study presents a data-driven framework for predicting the failure of smog mitigation methods based on meteorological conditions. Unlike existing approaches that primarily focus only on air quality prediction, this work identifies specific environmental conditions, along with AQI as an input feature, to determine when mitigation strategies become ineffective. This enables proactive decision-making to maintain healthy indoor air quality. A threshold-controlled indoor air purification system that self-activates when the model predicts mitigation failure using real-time sensor inputs is introduced to address outdoor mitigation restrictions. PM_2.5 reduction efficiency, clean air delivery rate, and energy consumption indicators are used to evaluate the purifier’s optimized performance. Predicting mitigation failure rather than just pollution levels and connecting it with an intelligent interior reaction mechanism is what makes this research novel. In a comparative analysis, Random Forest outperforms XGBoost with an accuracy of 95.5% as opposed to 94.5%, as well as higher precision (96.9%), recall (96.1%), and F1-score (96.5%). The purifier lowered indoor AQI from dangerous to safe levels within 30–40 min. Full article

Solid amine adsorbents can capture CO₂ at indoor-relevant concentrations (~1000 ppm), but many high-capacity adsorbents rely on granular or powdery supports that are difficult to integrate directly into air purification systems. Here, we applied three amination strategies to commercial fibrous substrates: bridge-grafting on viscose (TEPA-AMVF), direct grafting on polyacrylonitrile (TEPA-PAN), and physical impregnation on pore-engineered activated carbon fibre felt (PEI-ACF). These adsorbents were systematically screened under simulated indoor conditions (1000 ppm CO₂, 27 °C, 50% RH). A significant capacity difference was observed: TEPA-AMVF (24.8 mg g⁻¹) < TEPA-PAN (35.8 mg g⁻¹) ≪ PEI-ACF (97.0 mg g⁻¹). The superior performance of PEI-ACF was attributed to KOH activation, which produced a mesopore-rich structure (average pore diameter 26.1 nm at an optimal KOH/carbon ratio of 1.25) and enabled high nominal amine utilisation (0.19 mmol CO₂ mmol N⁻¹). PEI-ACF maintained high breakthrough-derived CO₂ uptake across realistic indoor conditions (64.2–118.6 mg g⁻¹ over 0%–100% RH; 71.6–124.5 mg g⁻¹ over 400–5000 ppm CO₂), exhibited rapid kinetics (pseudo-first-order rate constant k = 1.77 h⁻¹; 81.7% of equilibrium uptake within 1 h), and showed stable but partial regeneration over four adsorption–desorption cycles at 60–70 °C under N₂. Compared with granular or resin-based amine sorbents, the self-supporting PEI-ACF felt is expected to offer practical advantages for filter-integrated CO₂ removal, including mechanical integrity under airflow, reduced risk of particle leakage, and compatibility with HVAC filter slots. Remaining challenges include direct pressure-drop validation, operation in O₂-containing indoor air, long-term cycling, and management of CO₂ released during regeneration. Full article

Fine particulate matter (PM)-induced pollution is one of the major causes of indoor air quality deterioration. Passive air purification technologies offer advantages of structural simplicity and low energy consumption, yet their spatiotemporal mass transfer characteristics remain poorly understood. This study presents a theoretical and experimental investigation of PM spatiotemporal mass transfer under the sink effect induced by an electro-convective passive air purifier. The apparent mass transfer coefficient (D_app) and PM concentration prediction models based on Fick’s second law were established, and then the space-and-time-dependent mass transfer coefficient (D_st) was determined by using the Boltzmann–Matano method. The results revealed that the absolute values of D_st quantified local migration intensity, while its sign provided directional information unattainable from conventional averaged parameters. The logarithmic values of D_app showed a consistent logarithmic relationship with distance at fixed time windows, and the validated prediction model maintained errors within ±15%, enabling accurate reconstruction of full-field concentration distributions from limited measurement points. The complementary nature of these two coefficients offers a comprehensive evaluation framework. This work advances both the theoretical understanding and practical application of passive air purification technology, offering new tools for indoor PM exposure control and purifier performance optimization. Full article

Indoor air pollution, listed by the World Health Organization (WHO) as one of the top 10 environmental risk factors for human health, significantly elevates the risk of respiratory diseases, cardiovascular diseases, and cancers upon long-term exposure. Traditional indoor air purification technologies dominated by physical adsorption and filtration have inherent limitations, including mere pollutant phase transfer, easy saturation, and secondary pollution, while chemical purification centered on pollutant mineralization and degradation is the core development direction for radical elimination of indoor air pollution. Novel nanomaterials, featuring ultra-high specific surface area, precisely tunable active sites and electronic structures, and excellent room-temperature catalytic activity, have become the research focus in this field. This review systematically summarizes the characteristics of typical indoor air pollutants and purification scenario requirements, clarifies the core advantages of chemical purification technologies, details the research progress of novel nanomaterial systems in indoor air chemical purification, and dissects the reaction mechanisms and material optimization strategies of core pathways (photocatalysis, room-temperature thermal catalysis, electrocatalysis, plasma catalysis). We also outline the engineering application status and bottlenecks of these nanomaterials, propose systematic future development directions targeting existing challenges, and aim to provide a reference for fundamental research and industrial application of novel nanomaterials in indoor air purification. Full article

This study investigates whether a university teaching complex equipped with CSA S600 continuous air purification and sanitation units can maintain indoor air quality (IAQ) within recommended thresholds under real occupancy conditions and evaluates the impact of renovation works on IAQ. The work provides the first real-world assessment of the CSA S600 integrated monitoring system in an academic environment. CO₂, PM_2.5, PM₁₀ and VOCs were continuously measured over three months; moreover, indoor PM₁₀ values were compared with outdoor data from the regional monitoring network. Indoor CO₂ generally remained below 800 ppm, with short peaks of 1000–1500 ppm during high occupancy. PM_2.5 and PM₁₀ consistently stayed below the latest WHO guidelines, showing uniform recurring temporal patterns overtime; furthermore, indoor PM₁₀ showed limited coupling with outdoor trends, indicating the predominance of internal sources and ventilation dynamics. After renovation of the main Lecture Hall, particulate levels remained low, while VOCs showed a modest increase attributable to new materials. Overall, the findings demonstrate that the CSA S600 system effectively supports healthy IAQ in educational settings and that continuous monitoring is essential for managing occupancy-driven fluctuations and assessing the effects of structural interventions. Full article

Driven by global urbanization and increasing emphasis on sustainable building practices, indoor volatile organic compounds (VOCs) have emerged as a major environmental and health challenge. This review specifically focuses on room-temperature air-only catalytic oxidation of representative indoor VOCs under a recently matured and highly application-relevant research direction. Recent advances are systematically summarized, highlighting catalyst design strategies, air-phase reaction mechanisms, and performance of noble metal catalysts (NMCs), transition metal oxides (TMOs), bimetallic synergistic catalysts (BSCs), and single-atom catalysts (SACs). Emphasis is placed on thermodynamic feasibility, reaction kinetics, oxidation behavior of non-formaldehyde VOCs, and mechanistic insights associated with SACs interfacial synergy, which enable efficient O₂ activation, high selectivity, and operational stability without external oxidants even under high VOC concentrations. This review provides theoretical foundations and technical guidance for VOCs mitigation and supports the advancement of green, low-carbon, and safe indoor air purification strategies worldwide. Full article

Climate chambers enable repeatable indoor boundary conditions and are increasingly used to study multi-domain IEQ. However, thermal comfort and IAQ are still often evaluated separately, limiting evidence on their coupled behavior and potential trade-offs under different ventilation and air-cleaning strategies. The present study was carried out in the climate chamber located in the laboratory facilities of the University of Western Macedonia to quantify thermal comfort and IAQ simultaneously across different experimental scenarios that vary ventilation mode, heating operation, and occupancy. The results show a correlation between subjective and objective measurements, with the comfort temperature varying around 22.2 °C, as estimated by the Griffiths model, while ventilation mainly affects the stability of the thermal environment. CO₂ levels scaled with occupancy and ventilation rate, while PM removal was strongly strategy-dependent: after a controlled smoke event, mechanical ventilation plus air purification achieved the fastest decay and recovery toward near-background concentrations. Overall, this work represents a first step toward coupled IEQ research by jointly quantifying thermal comfort and IAQ in a climate chamber, enabling systematic comparison of ventilation strategies in terms of both perceived comfort and pollutant exposure. Full article

This study aims to address the lack of systematic research on how air filter cleaning affects pollutant distribution in subway stations, an urgent issue for ensuring indoor air quality in enclosed underground transit environments. Taking a representative subway line in Xi’an, China, as the research object, we monitored and analyzed pollutant concentrations (including particulate matter and microorganisms) at air supply outlets (near, semi-far, and far from the air filter) and different locations in a single station hall before and after filter cleaning, with the goal of clarifying the cleaning effect and its variation with distance from the air supply. The results show that, before cleaning, pollutant distribution exhibits distinct spatial characteristics: PM₁₀ concentration is 16.7% higher at outlets closer to the filter, while PM_2.5 and PM_1.0 concentrations are 22.4% and 19.7% higher at distant outlets, respectively. After cleaning, all pollutants are significantly reduced: PM₁₀ at near outlets decreases by 25.9%, PM_2.5 and PM_1.0 at far outlets drop by 44.2% and 42.7%, respectively, and the total numbers of bacteria and fungi in the air supply meet national hygiene standards. A key novel finding is that cleaning has differentiated effects on particle sizes across locations; it is more effective for larger particles at near outlets and for smaller particles at far outlets. This research not only quantifies the purification effect of filter cleaning but also reveals the spatial variation law of its impact, providing practical guidance for optimizing subway ventilation system maintenance (e.g., tailored cleaning strategies for different locations) and ensuring passenger health. Full article

Limonene is one of the most abundant, natural, bio-based monoterpenes. In recent years, it has attracted growing attention in both industrial and scientific communities due to its versatile physicochemical properties and wide spectrum of biological activities, including antimicrobial, antioxidant, and anti-inflammatory effects. Its renewable origin and biodegradability make limonene an ideal candidate for sustainable development and as a key building block in green chemistry. The industrial relevance of limonene spans multiple sectors, ranging from its use as a solvent and flavoring agent to its application in pharmaceuticals, cosmetics, polymers, and renewable fuels. Nevertheless, despite its numerous advantages, certain limitations and safety concerns have emerged. Prolonged or high-level exposure may result in sensitization, irritant reactions, or secondary oxidation products that pose potential health risks. Moreover, its oxidative instability can lead to the formation of reactive compounds under specific environmental conditions that influence indoor air quality and may contribute to secondary organic aerosol formation. Current research focuses on several key challenges: improving extraction and purification yields through biotechnological and enzymatic pathways; enhancing oxidative stability via encapsulation or chemical modification; and standardizing toxicological assessment protocols for both occupational and clinical settings. In this review, we analyze and discuss studies published predominantly in the last five years that explore the dual nature of limonene, its valuable industrial applications and its potential environmental and health-related challenges. Full article

Low-concentration trichloroethylene (TCE) and tetrachloroethylene (PCE) indoors pose a significant threat to human health due to their potent carcinogenic properties. However, existing research has predominantly focused on high-concentration scenarios in industrial settings, offering limited guidance for indoor air purification. This study investigated the adsorption mechanisms and performance regulation of coconut shell activated carbon for TCE/PCE through experimental analysis, molecular simulations, and dynamic modeling. Experimental results demonstrated that PCE, characterized by its non-polar nature and high boiling point, exhibited a substantially higher adsorption capacity than TCE. Increased humidity induced competitive adsorption between water molecules and pollutants, reducing the adsorption capacity of PCE by approximately 30%. Molecular simulations validated that water molecules occupied the active sites of oxygen-containing functional groups and pores, impeding the diffusion of TCE/PCE, while the non-polar surface of activated carbon preferentially adsorbs PCE. A dynamic prediction model developed in this study accurately forecasted breakthrough curves under varying pollutant concentrations, temperatures, humidities, and air velocities and quantified the service life of activated carbon. Response surface methodology revealed that controlling inlet concentrations (TCE < 7 ppb, PCE < 30 ppb), air velocity (<1 m/s), humidity (<50%), and temperature (<25 °C) can extend the service life of activated carbon to 3–5 months. Full article