Indoor air最新文献

Mental health is a significant concern for teenagers. Given that about 80% of Chinese high school students spend the majority of their time indoors on campus, school environments present opportunities not just for learning but also for reducing students’ stress and promoting their well-being. Previous research has shown that direct interactions with natural elements such as green plants have restorative effects, but limited attention has been given to indirect interactions with nature. We investigated the impact of three design forms—nonbiophilic, curved, and biomimicry—within school corridors and classrooms on Chinese high school students’ stress and cognitive functions. We employed a combination of subjective assessments and objective measurements to examine the protective and restorative impacts of these three design forms and utilized virtual 3D models in order to control confounding environmental variables during a visual experience. Through virtual reality simulations involving 96 participants, we collected physiological responses, including skin conductance level, heart rate, indicators of heart rate variability, and cognitive responses, including creativity and attention test scores, to evaluate participants’ changes in stress levels and cognitive performance. Our results indicated that indirect exposure to nature, particularly curved forms, facilitates greater cognitive improvement and stress reduction, whereas nonbiophilic forms offer enhanced stress protection benefits. Therefore, learning environments with nonbiophilic design may be more suitable for tasks that induce stress, such as classes and examinations. Learning environments that feature curved biophilic forms may be better suited for promoting relaxation, creativity, and attention.

This study developed and evaluated an optimal ventilation strategy for variable air volume (VAV) systems, targeting carbon dioxide (CO₂) and particulate matter less than 2.5 μm in diameter (PM_2.5) concentrations. The strategy integrates system-level demand-controlled ventilation (DCV) based on real-time occupancy data and zone-level predictive control using indoor air quality (IAQ) prediction models. By predicting indoor CO₂ and PM_2.5 levels for the subsequent time step and dynamically adjusting control priorities, optimal airflow is determined. A co-simulation model integrating EnergyPlus, CONTAM, and Python was employed for model training and testing. The proposed strategy was compared with on–off control, CO₂ predictive control, and PM_2.5 predictive control, demonstrating superior prediction accuracy and stable IAQ maintenance. The optimal ventilation strategy achieved the highest performance, maintaining CO₂ and PM_2.5 levels below their respective upper limits of 100% and 97.33% of the time. Although this strategy resulted in slightly higher energy consumption compared to the other control algorithms due to its multivariable control approach, it effectively maintained IAQ standards. This method simplifies development and maintenance by circumventing the need for complex optimization, providing a flexible and cost-effective solution for IAQ management. Future research will focus on developing integrated VAV system control strategies that ensure comfort year-round, addressing both energy efficiency and thermal comfort.

In order to explore reasonable prebedtime interventions to improve the sleep quality of the youth population, this experiment comprehensively investigated the effect of prebedtime footbath on the improvement of youth sleep quality. The experimental conditions of the experimental group were to take a 30-min footbath at 40°C 1 h before bedtime, to compare the experiment with the control group that did not take footbath, and to strictly control other environmental parameters that may affect sleep quality. We recorded the sleep of 16 male subjects using a subjective sleep quality questionnaire and polysomnography (PSG) and recorded their distal skin temperature (DST) and proximal skin temperature (PST) during footbath and sleep using temperature records. The skin temperature data showed that footbath before bedtime helped to increase DST and accelerate heat dissipation from the terminal skin, which in turn increased the distal–proximal skin temperature gradient (DPG), and we found that the DPG of the experimental group was higher than that of the control group for 84.8% of the time during the whole night’s sleep. Both subjective questionnaire and PSG monitoring results showed that sleep quality and sleep calmness could be effectively improved by taking a 30-min 40°C bedtime footbath 1 h before bedtime. The subjective sleep quality questionnaire score of the control group was only 84.1% of that of the experimental group. There were significant differences between the control and experimental groups in total sleep time (TST), sleep-onset latency (SOL), wake after sleep onset (WASO), and arousal index (AI) (p < 0.05). Compared to the control group, the experimental group showed a 43.4-min increase in TST, a 14.9-min decrease in SOL, a 32-min decrease in WASO, a 3.28 beats/hour decrease in AI, and a 9.0% increase in sleep efficiency by performing a prebedtime footbath. This study quantitatively describes the effect of prebedtime footbath on the improvement of sleep quality in young men and provides an effective reference for the rational improvement of sleep quality in young people.

Traditional gravimetric instruments used for personal air pollution exposure measurements are often cumbersome and noisy and do not offer real-time assessment capability. The Enhanced Children’s MicroPEM (ECM) is a comparatively lightweight and quiet instrument designed to capture both integrated filter-based gravimetric samples and real-time continuous (nephelometric) particulate matter with an aerodynamic diameter of 2.5 μm or less (PM_2.5) concentrations. We assessed the performance and reliability of collocated ECMs in a subset of pregnant women participating in a randomized controlled trial in Guatemala to test a liquefied petroleum gas (LPG) cookstove (intervention) versus biomass (control) for cooking. We compared average daily (24 h) PM_2.5 concentrations for the paired gravimetric (n = 219) and paired adjusted nephelometric (n = 221) samples using Spearman correlation and Bland–Altman agreement; we also assessed reliability based on the intraclass correlation coefficient (ICC) and root mean square error (RMSE). Median PM_2.5 gravimetric concentrations were 93.5 μg/m³ (interquartile range (IQR) = 52.6–160.5) and 21.4 μg/m³ (IQR = 12.0–32.0) in the control and LPG intervention groups, respectively; the median adjusted nephelometric concentrations were 83.7 μg/m³ (IQR = 47.6–148.9) and 22.6 μg/m³ (IQR = 17.5–29.7) in the control and LPG groups, respectively. Spearman correlations were higher in the control arm (0.91) than in the LPG intervention arm (0.67) in the gravimetric comparisons. The same trend was observed for adjusted nephelometric measurements in the control (0.92) and intervention arms (0.75). ICC values were high in both gravimetric (0.93) and nephelometric (0.95) collocations. Small differences in RMSE were observed for the gravimetric (26.69 μg/m³) and nephelometric collocations (31.76 μg/m³). Our findings demonstrate strong reliability between collocated ECMs for both gravimetric and adjusted nephelometric PM_2.5 personal exposure samples in rural Guatemala.

Trial Registration: ClinicalTrials.gov identifier: NCT02944682

Given that people spend on average more than 80% of their time indoors, monitoring indoor air quality (IAQ) is of the utmost importance for the safeguard of human health. Indeed, due to penetration from outdoors and the presence of specific indoor sources, poor IAQ is not uncommon. The use of portable air cleaners (PACs) is one of many options to improve IAQ. The market offers many products, but not all of them have reliable documentation on their effectiveness. Literature standard methods for testing PACs toward pollutants require extensive resources. In this work, we developed a new laboratory scale methodology based on a small, easy to use, economical batch system to test the efficiency of PACs. With this method, three commercial PACs were successfully tested for effectiveness toward volatile organic compounds (VOCs) and particulate matter (PM). The method proved successful, and the results highlighted the importance of conducting these tests, in addition to field investigations.

Mastering the characteristics of gas–liquid humidification jets at low pressure is fundamental for creating indoor humidity environments on the Qinghai-Xizang Plateau. In this paper, we numerically simulate gas–liquid two-phase jets at 50.0–101.3 kPa and analyze their flow, mass transfer, and heat transfer properties based on relevant dimensionless numbers. The results show that, for Reynolds number (Re) = 1652–9914 at low pressure, the jet axis velocity decays more slowly, the entrainment between the jet boundary and ambient air is enhanced, and the momentum diffusion range is larger. Specifically, at Re = 1652, the average jet axis velocity of 50.0 kPa is 0.13 m/s higher than that of 101.3 kPa. The jet dimensionless velocity distribution of each radial section obeys the Voigt curve. Under low-pressure conditions, the humidity diffusion range of the jet expands, while the temperature diffusion range decreases. The jet flow trajectory and velocity distribution are highly dependent on Re and Froude number (Fr), and temperature distribution depends significantly on Prandtl number (Pr) and Re. The jet humidity distribution highly depends on Schmidt number (Sc) when Re = 1652 and Re = 4957–9914, while showing weaker dependence on Sc for Re = 1652–4957. This study is aimed at enhancing the theory of gas–liquid jet flow and providing theoretical guidance for developing indoor humidity environment construction techniques at low pressure, thereby improving the livability of plateau buildings.

The levels of gas and particulate pollutants were measured inside and outside of a primary school classroom located in a suburban area in the city of Patras, Greece, during wintertime to evaluate the indoor air quality, identify potential problems, and determine the effectiveness of ventilation. The Foundation for Research and Technology–Hellas (FORTH) mobile laboratory was deployed, and a switching valve system was used to obtain both indoor and outdoor measurements. The outdoor air was the main source of in-classroom pollutants, as the windows remained partially open. Ventilation of the classroom was achieved naturally through the windows, and it was continuous during school hours, maintaining the pollutant concentrations at low levels, with average fine particulate matter equal to 2.6 μg m⁻³ and total aromatic and oxygenated volatile organic compound (VOC) levels in the order of 10 ppb. The levels of all measured pollutants were lower than the World Health Organization (WHO) safety limits, and they are not expected to affect the health of the students. Good air quality was observed within the classroom, showing the effectiveness of natural ventilation in this setting. Cleaning activities were a source of VOCs outside school hours, resulting in increases in the levels of VOCs of a few parts per billion. However, these concentrations were gradually reduced, and they did not reduce the indoor air quality the next school day. A box model was used to estimate an effective air exchange rate of 3.5 h⁻¹ during school hours.

Given the concerns surrounding the possibility of crosscontamination caused by the airborne transmission of respiratory aerosols (> 5 μm in diameter) and droplets (> 5 μm in diameter) containing infectious viruses, there is a great need for simulations that reliably characterize the behaviour of these particles in real-world scenarios. This study performs a comprehensive transient CFD analysis to investigate the transmission of virus-carrying aerosols and droplets released through coughing by a mobile patient within a typical room equipped with a ventilation system. This computational study elaborately examines how particle size and relative humidity impact the dispersion of aerosols and droplets carrying virus in both mobile and stationary conditions of patients. To enhance the accuracy of this study, effective factors such as evaporation of liquid content within aerosols and droplets and random distribution of the particles, along with considerations for buoyancy, drag, lift, Brownian motion, and gravitational forces, are taken into account. To investigate the influence of aerosol and droplet size, this study considers uniform size distributions of 1, 10, and 100 μm in diameter, comprising 98.2% liquid water and 1.8% solid content. Additionally, different relative humidity levels, 0%, 50%, and 90%, are incorporated to indicate their impact on the dispersion pattern and residence time of the particles in both stationary and dynamic scenarios. According to the results, high levels of relative humidity and individuals’ movement significantly affect the turbulence intensity, airflow pattern, travelling distance, residence time and trajectory of particles, air pressure, and density distributions in such environments.

Cooking activities are responsible for substantial emissions of both particulate matter (PM) and volatile organic compounds (VOCs), two key indoor air pollutants, which can lead to numerous adverse health effects, including premature mortality. Chicken breast was prepared following tightly constrained cooking procedures with contrasting cooking methods in a well-controlled research kitchen to investigate the PM and VOC emissions by simultaneous measurements with reference instruments (an optical aerosol spectrometer measuring light scattering of single particles for continuous PM monitoring and a proton-transfer-reaction time-of-flight mass spectrometer [PTR-ToF-MS] for VOCs). Peak concentrations of PM_2.5 ranked in the order (median [μg m⁻³]) pan-frying (92.9), stir-frying (26.7), deep-frying (7.7), boiling (0.7), and air-frying (0.6). Peak concentrations of VOCs ranked in the order (median [ppb]) pan-frying (260), deep-frying (230), stir-frying (110), boiling (30), and air-frying (20). Key VOCs from different frying methods were identified in a detailed principal component analysis (PCA), including aldehydes, ketones, furans, aromatic hydrocarbons, alkenes, pyrazines, and alkanes. The cooking temperature was found to be the key factor that positively correlated with both PM and VOC emission strength, while the oil weight was negatively correlated with the PM levels. We also determined PM emission rates (varying over a wide range, e.g., for PM_2.5 from 0.1 to 2931 μg min⁻¹) and PM exposures (ranging, e.g., for PM_2.5 from approximately 2 to more than 1000 μg m⁻³ min). In addition, by using EPR spectroscopy, we measured environmentally persistent free radicals (EPFRs) that formed from heating and cooking processes at levels of approximately 10⁹ spins μg⁻¹ of PM mass. These EPFR concentrations were shown to be unaffected by ozone exposure.

The thermal perception of the human body changes with seasons. The seasonal variation of subjective thermal responses and the separation of thermal sensation and thermal comfort were studied in this paper. A new evaluation index of thermal comfort was proposed. The study was based on field surveys of 32 university students in Jiaozuo city in the cold climate zone of China. Totally, 854 valid datasets were obtained. Results indicated that the environmental parameters, clothing insulation, subjective responses and mean skin temperature were all affected by seasonal variations. The mean skin temperature increased with the rise of indoor air temperature. The influence of season changes on the difference between mean skin temperature and indoor air temperature (T_dif) was obvious. The separation of thermal comfort and thermal sensation was obvious in the four seasons. TSVs deviated 0.76, 1.13, 0.83, and 1.37 units from the thermal neutrality when TCVs were the lowest in the four seasons, respectively. The separations were more obvious in seasons with extreme climates (summer and winter) than in transition seasons with mild climates (spring and autumn). People’s emotion was affected by the thermal environment. The hotness in summer increased “boring” feelings, and the coldness in winter reduced people’s pleasantness. T_dif was proposed as a reflection of human thermoregulation. An optimal T_dif range between 6.0°C and 12.0°C was proposed, in which optimal thermal and emotional conditions were achieved. The study provides a theoretical basis for the seasonal study of human thermal response and the dynamic control of the indoor environment in the future.