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Most studies on Chinese dormitories are carried out in summer, while few focus on a transition season or winter. This study evaluated the air quality of a student dormitory in a university in the Beijing area by using a questionnaire survey and on-site measurements. The CO2 concentration was used as an indoor air quality evaluation index to characterize the freshness of the air, and different window opening conditions in the dormitory were simulated, with corresponding improvement plans proposed. The results of this study revealed that the air quality and thermal comfort of the student dormitories during a transition season and winter fell short of expectations. According to the survey, students who opened their windows frequently had a better subjective perception of the air quality. However, due to the large temperature difference between day and night, more than 80% of the students felt too cold when opening the windows. For daytime conditions, the area of unilateral ventilation window opening should not be less than 0.39 m2, the area of bilateral ventilation window opening should not be less than 0.13 m2, and the time taken to close the windows and doors should not exceed the maximum ventilation interval. Empirical equations were fitted for nighttime conditions based on the CO2 concentration, number of people in the room, and window opening area, resulting in a reasonable window opening area of 0.349 m2~0.457 m2. In sum, this study assessed the air quality status within typical university dormitories across varying seasons, gaining a clear understanding of how different ventilation strategies and occupant densities influence air freshness and thermal comfort. Based on these insights, a practical and optimized window area recommendation was formulated to enhance the indoor environmental quality in these dormitories. [ABSTRACT FROM AUTHOR]

The air quality in classrooms significantly impacts school children's health and learning performance. It has been reported worldwide that classroom air quality does not meet the required standard and actions are pledged for improvement. However, it poses a challenge for decision-making in terms of prioritising taking-up measures. The aim of this study is to propose a method of identifying the action measures for improving classroom air quality and prioritising them. Case studies in the UK and China were conducted, and the key measures were identified through literature studies, open-ended questionnaire surveys, and workshop discussions, which are classified into three categories: B1, policy; B2, technology; and B3, information sharing. The analytical hierarchy process (AHP) is applied in the prioritisation of the action measures. A total of 138 teachers and parents from China and the UK participated in this case study. The genetic algorithm-optimised Hadamard product (GAOHP) method is applied to justify the consistency ratio (CR) within the required threshold value in order to ensure the consistency of the subjective perception and the accuracy of comparative weights. The results show that item B2, technology, is the most desired measure by both Chinese and British parents and teachers, despite the deviation from the optimal choice in China and the UK. Among the proposed action measures, the UK respondents strongly expected air purifiers with natural ventilation as opposed to their Chinese counterparts preferring to share the real-time status of classroom air quality. Our work will provide strong support for the subsequent selection of indoor air quality improvement strategies for schools. [ABSTRACT FROM AUTHOR]

Clothing can absorb fine particulate pollutants from the atmosphere outdoors and then release them after entering the room in a form similar to three-handed smoke. In this study, the experimental site in Zhengzhou, a typical city with heavy pollution in central China, was used to investigate the adsorption and diffusion patterns of three different fabrics of polyester, polyester-cotton, and cotton clothing for fine particle pollutants, to guide people's behavior patterns and indoor air distribution, and to reduce indoor pollution exposure. The results showed that when garments of three different fabrics were exposed to moderate and heavy PM2.5 pollution for 1 h, 2 h, and 3 h, respectively, and then transferred to the diffusion chamber, polyester always released the highest PM2.5 concentration to indoor air during the same release cycle, followed by cotton and polyester-cotton. In addition, the concentration of indoor air pollutants will be periodically affected by the diffusion of fine particulate adsorbed by clothing fabrics. With the increase in outdoor pollution and exposure duration, the indoor PM2.5 concentration takes longer to stabilize at certain levels after the clothing is transferred to the indoor side. Finally, the comparison of natural ventilation experiments proved that it is not feasible to rely solely on natural ventilation to improve the influence of clothing pollution sources on indoor air quality. [ABSTRACT FROM AUTHOR]

In recent years, the indoor air quality (IAQ) of educational buildings has attracted people's attention. As a resting place, the dormitory occupies more than half of the students' time in school. During sleep, the IAQ in dormitories is easily affected by breathing, which in turn affects the sleep quality and mental state of students. In order to study the relevant IAQ during sleep, this paper selected the dormitories of graduate students of different grades in a university in northern China, and monitored the temperature, humidity, CO2, PM2.5, HCHO and TVOC for two weeks during the changing seasons of autumn and winter. In addition, by issuing questionnaires, students made a subjective evaluation of the IAQ. According to the results of objective monitoring data and subjective evaluation, the IAQ changes in student dormitories of different grades, genders, and locations are statistically analyzed, and the correlation between environmental parameters is discussed. The research results show that temperature and humidity basically meet the national standards; indoor PM2.5 is positively correlated with outdoor PM2.5; and HCHO and TVOC are positively correlated with indoor temperature and humidity. Most dormitories lack natural ventilation, and the concentration of CO2 during sleep is too high, which affects the quality of sleep and mental state. [ABSTRACT FROM AUTHOR]

Antenatal depression is associated with adverse birth and long‐term outcomes for mothers and children. Pregnant women spend 90% of time indoors; however, the association between indoor air quality and risk of antenatal depression has not been established. In this study, we aim to determine the total and trimester‐specific association of perceived indoor air quality (PIAQ) with antenatal depression. A total of 2166 pregnant women were enrolled during the first trimester and evaluated during the second and third trimesters in the China Medical University Birth Cohort Study, a prospective pre‐birth cohort study in northeastern China. PIAQ scores were obtained during each of three trimesters, which a higher score indicated a worse indoor air quality. Antenatal depression was screened using an Edinburgh Postnatal Depression Scale (EPDS) and defined as an EPDS score ≥ 9. Prevalence of antenatal depression was 26.7%, 20.6%, and 20.9% during the first, second, and third trimesters, respectively. A higher PIAQ score was positively associated with a depression score throughout pregnancy (β = 0.27, 95% CI = 0.15–0.39). Trimester‐specific adverse PIAQ exposure was associated with a higher depression score in the same trimester, but not with a higher score in a subsequent trimester. A dose–response pattern and incremental increases in risk of depression were observed with calculated adverse PIAQ exposures across all three trimesters, with the highest risk (OR = 3.24; 95% CI = 2.28–4.78) among women with adverse PIAQ across all three trimesters. The hazardous association between adverse PIAQ exposure and risk of depression were less pronounced among women with higher physical activity levels (P for interaction < 0.001). The results of present study provided important evidence that pregnant women's mental health was linked to indoor air quality during pregnancy. These findings could be helpful in the development of guidelines to prevent antenatal depression by improving indoor air quality. [ABSTRACT FROM AUTHOR]

Exposure to formaldehyde causes a variety of adverse health outcomes, while the distributions of indoor formaldehyde in different building types are still not clear in China. In this study, based on the systematic review of previously published data and Monte Carlo simulation, we assessed geographical and temporal distributions of indoor formaldehyde concentrations in residences, schools, and offices across China. A total of 397 studies covered 34 provincial‐level regions since 1986 were collected. The results showed that indoor formaldehyde concentrations in residences, schools, and offices in nationwide were decreasing over years due to the publishment of indoor air quality standards since 2002. During 2011 to 2015, the median concentrations of indoor formaldehyde in newly renovated residences, schools, and offices were 153 μg/m3, 163 μg/m3, and 94 μg/m3, with an exceeding rate of 82%, 46%, and 91% considering a standard threshold of 100 μg/m3 at that time, while the exceeding rate was less than 5% for buildings that were renovated beyond one year. Our findings release the temporal trends and geographic distributions of indoor formaldehyde concentrations in residences, schools, and offices in China in the past 30 years, and provide basic data for the comprehensive evaluation of disease burden attributable to indoor formaldehyde exposure. [ABSTRACT FROM AUTHOR]

The last two decades have witnessed rapid urbanization and economic growth accompanied by severe indoor air pollution of volatile organic compounds (VOCs) in China. However, indoor VOC pollution across China has not been well characterized and documented. This study is a systematic review of field measurements of eight target VOCs (benzene, toluene, xylenes, acetaldehyde, p‐dichlorobenzene, butadiene, trichloroethylene, and tetrachloroethylene) in residences, offices, and schools in China from 2000 to 2021. The results show that indoor pollution of benzene, toluene, and xylenes has been more serious in China than in other countries. Spatiotemporal distribution shows lower indoor VOC levels in east and south‐east regions and a declining trend from 2000 to 2021. Moving into a dwelling more than 1 year after decoration and improving ventilation could significantly reduce exposure to indoor VOCs. Reducing benzene exposure is urgently needed because it is associated with greater health risks (4.5 × 10−4 for lifetime cancer risk and 8.3 for hazard quotient) than any other VOCs. The present study enriches the database of indoor VOC levels and provides scientific evidence for improving national indoor air quality standards as well as estimating the attributable disease burden caused by VOCs in China. [ABSTRACT FROM AUTHOR]

The residential indoor environment and health have received increasing public interest recently. To improve knowledge of impacts of the residential indoor environment on health status of inhabitants, a Chinese Residential Indoor Environment and Health (CRIEH) survey was conducted from March 2014 to June 2014, and provided the information on 7934 residents in ten provinces and two municipalities. Results showed that prominent indoor environmental issues of households reporting were: "thermal problems in summer" (55%) in the living room; "low humidity in winter" (51%) in the bedroom; "odor" (39%) in the kitchen; "thermal problems in winter" (52%) in the toilet. Moreover, there were significant associations between indoor environment components and self-reported health. The largest association coefficient was found between safety and overall health (0.40). There was a relatively large association coefficient between safety and chronic pain such as joint pain (0.31) and lower back pain (0.29). Allergies had a relatively large coefficient with indoor air quality (0.36). Furthermore, significant associations with the overall indoor environment quality were found for self-reported health even after adjusting for personal characteristics. This study will promote understanding of the complex relationships between the residential indoor environment and occupants' health in China. [ABSTRACT FROM AUTHOR]

The coronavirus (COVID‐19) lockdown in China is thought to have reduced air pollution emissions due to reduced human mobility and economic activities. Few studies have assessed the impacts of COVID‐19 on community and indoor air quality in environments with diverse socioeconomic and household energy use patterns. The main goal of this study was to evaluate whether indoor and community air pollution differed before, during, and after the COVID‐19 lockdown in homes with different energy use patterns. Using calibrated real‐time PM2.5 sensors, we measured indoor and community air quality in 147 homes from 30 villages in Beijing over 4 months including periods before, during, and after the COVID‐19 lockdown. Community pollution was higher during the lockdown (61 ± 47 μg/m3) compared with before (45 ± 35 μg/m3, p < 0.001) and after (47 ± 37 μg/m3, p < 0.001) the lockdown. However, we did not observe significantly increased indoor PM2.5 during the COVID‐19 lockdown. Indoor‐generated PM2.5 in homes using clean energy for heating without smokers was the lowest compared with those using solid fuel with/without smokers, implying air pollutant emissions are reduced in homes using clean energy. Indoor air quality may not have been impacted by the COVID‐19 lockdown in rural settings in China and appeared to be more impacted by the household energy choice and indoor smoking than the COVID‐19 lockdown. As clean energy transitions occurred in rural households in northern China, our work highlights the importance of understanding multiple possible indoor sources to interpret the impacts of interventions, intended or otherwise. [ABSTRACT FROM AUTHOR]

In Chinese northwestern rural households where the indoor air quality is worse than the outside, rural residents face much higher health risks than urban residents. In this study, remote physical sensor devices and detectors technology were used to monitor and calculate the dwelling environmental quality index of 12 dwellings of traditional villages in the Hehuang area of China based on four environmental parameters to assess the indoor air quality of local dwellings. The results show that (1) the DEQI value reached 76 in summer but only 50 in winter, and the indoor dwelling environment quality in the Hehuang area was better in summer than in winter. (2) The S T was only 34 in summer and even lower in winter, at only 10, and low indoor temperatures were a chronic problem for the indoor dwelling spaces throughout the year. (3) In both summer and winter, the S RH reached 86, which was satisfactory overall. (4) In summer, the S CO2 value was 89 and the S PM10 value was 96, reflecting relatively good overall conditions. In winter, the S CO2 value was 65, the concentrations generally increased, and the S PM10 value was equal to 40, with concentrations exceeding the national standard value more than half the time. This study enables local governments and residents to accurately evaluate and analysis existing indoor dwelling environment problems based on this remote sensing technology, enhance the environmental health awareness of local residents, and provide an objective basis for improving the local dwelling environment and developing relevant policies. • The study conduct an evaluation of indoor dwelling environment with remote sensing. • The study make local governments and residents recognize indoor dwelling problems. • It provides better methods for evaluating indoor dwelling environments in rural areas. [ABSTRACT FROM AUTHOR]

[Display omitted] Particulate matter (PM) is an important air pollutant in subway systems. Exposure to high PM concentrations poses a threat to human health and raises concerns. Piston effect can provide the outdoor fresh air to subway stations through station exits, but it also brings PM from tunnels to platforms when the train enters the station. In this paper, a transient numerical model is developed according to an actual subway station and validated by field tests. The model is used to investigate PM 10 concentration at platform induced by train movement. The cumulative PM 10 concentration at platform in one day is calculated according to the train schedule. Platform screen door (PSD) with adjustable vents is studied to control the PM 10 level at platform and energy saving in 27 cities of five climatic zones in China are discussed. The results show that adjustable vent height should be less than 0.70 m to ensure that PM 10 concentrations at platform can be maintained at an acceptable level and the requirement of fresh air can be met. Moreover, energy consumption can be reduced by more than 70 % in different cities compared with the conventional mechanical ventilation system. The optimized adjustable vent can provide an important reference for improving indoor air quality (IAQ) and saving energy consumption of ventilation systems in underground facilities. [ABSTRACT FROM AUTHOR]

Due to considerable carbon emissions in building sectors, sustainability transformation is essential for power supply reliability, stability, grid-friendly interaction, and integration with e-transportation. However, building sustainability transformation requires inter-disciplinary and trans -disciplinary platforms for 'material-component-building-district' co-simulations and innovations. In this study, a generic methodology is proposed to comprehensively interconnect nano-scale material and energy systems in thermal transport and thermodynamics, guiding the design and operation for lifecycle sustainability, together with carbon intensity quantification and decarbonisation potential. Afterwards, a cross-scale energy simulation platform is formulated, involving nanoporous materials, innovative components, building integrations, and district energy analytics. The formulated platform can enable synthetical and comprehensive analysis on thermodynamic performances, energy performances, energy conversion and management, throughout integrated cross-disciplinary approaches by overcoming performance overestimation or underestimation of traditional single-stage approaches. The application of the platform quantifies the decreasing magnitude of energy consumption for PCM microcapsule wall, self-cleaning façade coating, clear thermal resistant cleaning glass coating, evaporative cooling & solar PV roof, volatile organic compound (VOC) absorption for indoor air quality (IAQ) control, building integrated photovoltaics (BIPVs), solar thermal collectors and 10-kW wind turbine. Afterwards, dynamic interaction between real buildings and digital twin models was realized for fast computation and prediction, labour cost and initial investment cost saving, long-term performance analysis. Both historical database and digital twin-generated database can promote the development of machine learning (ML) models, through data preparation, hyperparameter optimization, model training, testing, and validation. The proposed approach and formulated platform can enable synthetical and comprehensive analysis on building sustainability, throughout integrated cross-disciplinary approaches for 2060 carbon neutrality in China. [Display omitted] • A cross-scale simulation platform with nanoporous material and component innovation. • Climate change on thermodynamics and energy performance in thermal transport. • Quantification on carbon intensity and decarbonisation with technology innovations. • Roles of artificial intelligence in cross-scale energy simulations. • Climate adaption and model predictive control with hyperparameter optimization. [ABSTRACT FROM AUTHOR]

Particulate matter (PM) from different sources exhibits diverse chemical and physical characteristics, and it is an essential carrier of toxic chemicals. Ignoring PM properties is inappropriate for indoor air quality (IAQ) control in places with internal sources, such as metro stations. PM control measures aimed at health protection should be established based on PM health effects. The current PM control limit for metro stations may be insufficient for health protection. It is important to find a method that comprehensively evaluates PM features to set PM exposure limits. This study evaluated the health risks induced by chemical components and the oxidative potential of PM in the Tianjinzhan metro station. A PM control strategy was suggested based on health effect analysis. PM on the platform had notable underlying adverse health effects. An in-depth toxicology analysis was suggested to assess the high Ba and Mn concentrations in PM. The risk from Cr raised concern regarding the potential for carcinogenicity. As a potential composite index, the dithiothreitol (DTT) activity may be appropriate to evaluate the general adverse health effects caused by PM. The DTT activity of the platform was 3.3–5.4 times that of the ventilation shaft. Removing a unit mass of PM1 in the station hall would produce more health benefits than the removal of a unit mass of PM2.5. However, the DTT results indicated that control strategies on the platform should first focus on PM2.5, which would achieve the same protection effect as that when the PM1 mass concentration is decreased by the same level. A revision of the PM2.5 control limit for China metro stations was recommended to control oxidative potential on the platform. [Display omitted] • Indoor PM health effects could be quantified by oxidative potential using the DTT assay. • Railroad-related PM sources may lead to a potential health risk concern on the platform. • Removing a unit-weight PM2.5 from the platform brings the same health benefit as a unit-weight PM1. • PM control should focus on PM1 for the station hall, but PM2.5 for the platform. • The platform required air purification to control PM2.5 concentration. [ABSTRACT FROM AUTHOR]

Indoor air quality (IAQ) of urban public transportation stations (UPTS) has adverse health impacts on the station employees and commuters. However, there is a lack of comprehensively evaluations of IAQ in waiting rooms of UPTS. Therefore, it is crucial to select appropriate air quality indexes (including fuzzy synthetic index (B), comprehensive index (P), I 1 index, and indoor air quality index (IAQI)) to assess air quality and potential health risks. Our study is a subsample of the CPPEHS 2019 study, which included 224 UPTS in 126 cities of China. We found that P index showed an excellent air quality rate of 95.96% in the railway stations and 83.19% in the inter-city bus stations. The P index was correlated with UPTS usage years, useable area, and per passenger useable area. Furthermore, waiting rooms in UPTS with good (OR = 1.9187, 95% CI: 1.1204, 3.2859) and bad (OR = 2.0854, 95% CI: 1.2182, 3.5698) air quality evaluated by P index had a higher risk of rhinitis compared to those with excellent air quality. Similarly, UPTS with good (OR = 2.2202, 95% CI: 1.3427, 3.6711), bad (OR = 1.7897, 95% CI: 1.0807, 2.9637), and serious (OR = 1.7478, 95% CI: 1.0098, 3.0250) air quality evaluated by P index were associated with a higher risk of pharyngitis. These findings suggested that P index is the optimal index for assessing air quality in UPTS, while IAQI may exaggerate indoor air pollution and the B index may underestimate it. Overall, this study aims to identify and evaluate the more suitable air quality index (P) in nationwide UPTS, providing valuable insights for control of IAQ and guiding the air quality management and standards. • The evaluation of indoor air quality in urban public transportation stations (UPTS) currently lacks a reliable index. • Four indoor air indexes were calculated to evaluate the air quality of UPTS. • Comprehensive index (P) is the optimal index to evaluate the air quality and health risks in UPTS. [ABSTRACT FROM AUTHOR]

Heat recovery ventilation (HRV) is type of energy saving ventilation. It has been widely used in animal house to alleviate contradiction between thermal comfort and ventilation in recent years. However, air heat exchanger freeze of HRV caused by severe cold weather limited HRV application in northeast China. It is necessary to find an economic way to ensure HRV being operated without freezing. Establish a more reasonable integration of heating and ventilation system in severely cold area. An experiment was conducted in rabbit house during winter in Arun Banner, northeast China. The rabbit house was heated by a coal boiler in the next room. Hot water produced by boiler was supplied to heating radiator inside the rabbit house. The boiler room was warm because of some extra heat release by boiler. To prevent freezing, the boiler room was used to preheat cold fresh air before it entered the heat exchanger. The HRV was installed on the ground of the rabbit house. It was an integration of HRV and boiler heating system. Temperature, relative humidity and concentration of noxious was measured with automatic recording sensor instrument. Data was collected to evaluate the decrease in air pollutants and air temperature of the rabbit house. Preheating effect of the boiler room and the HRV were tested when the system was in operation. The performance of the HRV and prevention of freezing in heat exchanger was evaluated in typical cold weather in northeast China. The economic benefit of the system was analyzed. The results showed that when the HRV and boiler system began to operate, concentrations of ammonia (NH3) and carbon dioxide (CO2) in rabbit house dropped by 46% and 64%, respectively. Moreover, indoor air temperature only dropped by an average of 1.8 ℃ when the outdoor air temperature varied from -15.8 ℃ to -11.8 ℃. It means that the system can significantly improve indoor air quality with barely a slight decline of indoor air temperature. Respiratory and skin disease decreased by 16% and 4%, respectively. It is great potential for better health and production of rabbits. The boiler room heated fresh air from -13.8 ℃ to -3.7 ℃, and the HRV heated fresh air from -1.0 ℃ to 5.5 ℃ on average. No frozen of the heat exchanger was observed. Heated load of the boiler room and the heat recovery load of the HRV were 12.6 kW and 5.0 kW, respectively. Sensible heat recovery efficiency of the HRV was 75.6%. Coefficient of performance of the HRV was 6.2. The system was operated efficiently. The method of freezing prevention ensure HRV in good condition among the whole cold season in northeast China. It is an economic option because the system can operated without extra energy consumption. The return of investment is 3 years in this work condition. The integration of HRV and boiler allowed HRV and boiler heating to operate with high efficiency and solve the contradiction between heating and ventilation in severely cold weather in the rabbit house. This finding can provide a sound reference for the design of animal house heating and ventilation system in severely cold climate northeast China [ABSTRACT FROM AUTHOR]

Indoor air pollution resulting from volatile organic compounds (VOCs) is a significant health concern, especially formaldehyde. Therefore, predicting indoor formaldehyde concentration is essential for environmental control. In this research, the authors develop a thermal and wet coupling calculation model of porous fabric that considers the influence of different phases of wet components and the coupling effect of heat and humidity on formaldehyde migration. We propose a modified calculation method of the formaldehyde mass transfer characteristic parameters of fabric to obtain the diffusion coefficient D and partition coefficient K. The heat and humidity coupling model and formaldehyde mass transfer model of fabric are simultaneously solved, and the authors analyze the influence mechanism of fabric loading rate, fabric type, temperature, and humidity on indoor formaldehyde mass transfer characteristics. We study the variation trend of fabric formaldehyde mass transfer characteristics coefficient and the temporal and spatial distribution of indoor formaldehyde concentration. The theoretical model is applied to practical problems by pre-evaluating the indoor formaldehyde concentration of decorated residential buildings in typical climate areas of China before occupancy. The authors obtain the variation rule of indoor formaldehyde concentration of residential buildings under typical hot and humid climate conditions, building materials, furniture, and fabrics. To provide theoretical support for indoor environmental control and human health protection. [Display omitted] • The VOC mass transfer process and heat and moisture transfer process of fabric are considered in coupling. • The influence of different phases of wet components is considered on VOC migration. • A calculation method for fabric's VOC mass transfer characteristic parameters is proposed. • The influence mechanism of fabric loading rate, fabric type, temperature, and humidity on indoor VOC migration are analyzed. [ABSTRACT FROM AUTHOR]

[Display omitted] • State of the art on real-time sensors for indoor air evaluation is reviewed. • High spatiotemporal resolution data from real-time sensors is favorable for the risk assessment of indoor air pollution. • Challenges including performance, stability and calibration of sensors still remained. • Sensors with high performance, low price, and more target pollutants are expected. People generally spend most of their time indoors, making indoor air quality be of great significance to human health. Large spatiotemporal heterogeneity of indoor air pollution can be hardly captured by conventional filter-based monitoring but real-time monitoring. Real-time monitoring is conducive to change air assessment mode from static and sparse analysis to dynamic and massive analysis, and has made remarkable strides in indoor air evaluation. In this review, the state of art, strengths, challenges, and further development of real-time sensors used in indoor air evaluation are focused on. Researches using real-time sensors for indoor air evaluation have increased rapidly since 2018, and are mainly conducted in China and the USA, with the most frequently investigated air pollutants of PM 2.5. In addition to high spatiotemporal resolution, real-time sensors for indoor air evaluation have prominent advantages in 3-dimensional monitoring, pollution peak and source identification, and short-term health effect evaluation. Huge amounts of data from real-time sensors also facilitate the modeling and prediction of indoor air pollution. However, challenges still remain in extensive deployment of real-time sensors indoors, including the selection, performance, stability, as well as calibration of sensors. In future, sensors with high performance, long-term stability, low price, and low energy consumption are welcomed. Furthermore, more target air pollutants are also expected to be detected simultaneously by real-time sensors in indoor air monitoring. [ABSTRACT FROM AUTHOR]

[Display omitted] • The contribution of influential factors on the change of indoor PM 2.5 is evaluated. • A method for quantifying the monthly variation pattern of PM 2.5 concentrations. • The ambient PM 2.5 contributions are varied in each month. • N, M, and W-shaped PM 2.5 variation patterns are found from observed data. • Time-specific indoor air interventions can help seasonally target management. Indoor air quality is crucial to the physical and psychological health of students because they spend a large portion of their time in classrooms. Indoor PM 2.5 concentrations are affected by various complex factors, such as outdoor PM 2.5 , temperature, and relative humidity. However, how and to what extent these factors contribute to PM 2.5 concentrations remains unclear. Recently, black-box (e.g., neural networks) and white-box (e.g., linear regression) models have been applied to analyze their contributions. However, these models either have low interpretability or are insufficient for revealing complex nonlinear relationships. To address these issues, indoor PM 2.5 concentrations in ten classrooms were monitored for twelve months at a primary school in North China, and the contribution of various influential factors was calculated using partial derivatives based on this approach. This method can automatically identify linear and nonlinear relationship models from a large amount of data without a prior hypothesis. Experimental results showed that: (1) The contribution of each influential factor to indoor PM 2.5 varied greatly in the 12 months based on the identified relationships. In addition, no single relationship pattern was identified that could universally describe the factors influencing indoor PM 2.5. (2) The method developed in this study can automatically identify linear and nonlinear relationship models with white-box structures from a large amount of data without a prior hypothesis, which is more interpretable and applicable than other baselines. (3) Targeted solutions can be drawn by the contribution of each factor and three types of relationship curves (i.e., N -shaped, M−shaped, and W-shaped), the latter of which is the Pareto front revealed by our results. The study offers informative results regarding the temporal dynamics of indoor PM 2.5 concentrations and quantitative contributions of influential factors based on timely long-term data, which promotes the understanding of changes in indoor PM 2.5 concentrations. This also demonstrates the promising potential of using low-cost online sensors to conduct informative measurements that guide schools to more effectively improve classroom air quality. [ABSTRACT FROM AUTHOR]

The flow-field characteristics of high-temperature airflow and particle distributions generated from the running furnace during smelting process in foundry shop were studied by on-site measurements and theoretical analysis in this work. A theoretical model was proposed to describe the dispersion characteristics of the high-temperature buoyant jet flow and plume induced by the furnace with two typical opening modes. The coupling effects of the heat source features and environmental factors were emphatically discussed by comparing the trajectory, cross-section diameter, velocity and temperature decay, and volumetric flow rate during the dispersion process. Results show that in the large foundry shop with natural ventilation, there is a vertical temperature gradient of 0.1–0.4 °C/m, which can make the pollutant locked in the workshop and weaken the entrainment of the thermal flow. The crossflow is a non-negligible factor, which causes the dispersion trajectory of the pollutant flatter and induces a long travelling distance along the horizontal direction. The indoor particle concentration when the furnace opens concentration seriously exceeds the limits in the existing indoor air quality standard of China. This work is expected to give suggestions on ventilation designs and arrangements of the exhaust port or device in industrial environments. [ABSTRACT FROM AUTHOR]

[Display omitted] • Exposure inequality was contrary between ambient and household PM 2.5 exposure. • The poorest experienced the highest PM 2.5 exposure though ambient exposure was low. • Negative concentration index gradually increased indicating a transition towards equality. • Aggressive countermeasures reduced ambient exposures but benefited people disproportionately. • Spontaneous clean household energy transition effectively reduced the exposure inequality. The society has high concerns on the inequality that people are disproportionately exposed to ambient air pollution, but with more time spent indoors, the disparity in the total exposure considering both indoor and outdoor exposure has not been explored; and with the socioeconomical development and efforts in fighting against air pollution, it is unknown how the exposure inequality changed over time. Based on the city-level panel data, this study revealed the Concentration Index ( C ) in ambient PM 2.5 exposure inequality was positive, indicating the low-income group exposed to lower ambient PM 2.5 ; however, the total PM 2.5 exposure was negatively correlated with the income, showing a negative C value. The low-income population exposed to high PM 2.5 associated with larger contributions of indoor exposure from the residential emissions. The total PM 2.5 exposure caused 1.13 (0.63–1.73) million premature deaths in 2019, with only 14 % were high-income population. The toughest-ever air pollution countermeasures have reduced ambient PM 2.5 exposures effectively that, however, benefited the rich population more than the others. The transition to clean household energy sources significantly affected on indoor air quality improvements, as well as alleviation of ambient air pollution, resulting in notable reductions of the total PM 2.5 exposure and especially benefiting the low-income groups. The negative C values decreased from 2000 to 2019, indicating a significantly reducing trend in the total PM 2.5 exposure inequality over time. [ABSTRACT FROM AUTHOR]

Formaldehyde is concerned as an important indoor carcinogen. While contribution of outdoor formaldehyde to indoor concentration is recognized, long-term measurement about its impact on indoor environments remain missing. We measured both outdoor and indoor formaldehyde concentrations for over one year in Nanjing (east-central China) and calculated the outdoor/indoor (O/I) ratios. 64.8% of the measured outdoor concentration have exceeded the chronic reference exposure criteria of 0.009 mg/m3 set by Office of Environmental Health Hazard Assessment (OEHHA). The outdoor concentration was highest in summer with median value of 0.020 mg/m3 and lowest in spring with median value of 0.009 mg/m3. Diurnally, outdoor formaldehyde concentration was highest at noon with median value of 0.013 mg/m3 and lowest at night with median value of 0.01 mg/m3. Health analysis revealed that cancer risk by exposure to this concentration level is 1.6 × 10−4, higher than threshold limit of 10−6. In addition, the median O/I ratios are 0.18 and 0.27 in two offices, indicating that outdoor formaldehyde contributes to indoor concentrations by about one quarter. The change of O/I ratio also shows a similar seasonal and diurnal trend as outdoor concentrations (highest in the summer in a year and at noon in a day). Outdoor formaldehyde concentration is therefore not negligible as a contributor to indoor concentration, especially as indoor concentration limit gets continuously lowered. This factor should be taken into account in indoor air quality design and maintenance. [ABSTRACT FROM AUTHOR]

[Display omitted] • Our study indicates abrupt reductions in ambient PM 2.5 from lockdown in China. • The lockdown also led to significant increases in indoor PM 2.5 exposure. • Hundreds of premature deaths were added due to increased household PM 2.5. • Exposure to indoor air pollution is comparable to ambient air pollution exposure. • The lockdown caused an overall increase in integrated population weighted exposure. Ambient and household air pollution are found to lead to premature deaths from all-cause or cause-specific death. The national lockdown measures in China during COVID-19 were found to lead to abrupt changes in ambient surface air quality, but indoor air quality changes were neglected. In this study, we aim to investigate the impacts of lockdown measures on both ambient and household air pollution as well as the short-term health effects of air pollution changes. In this study, an up-to-date emission inventory from January to March 2020 in China was developed based on air quality observations in combination with emission-concentration response functions derived from chemical transport modeling. These emission inventories, together with the emissions data from 2017 to 2019, were fed into the state-of-the-art regional chemistry transport model to simulate the air quality in the North China Plain. A hypothetical scenario assuming no lockdown effects in 2020 was also performed to determine the effects of the lockdown on air quality in 2020. A difference-to-difference approach was adopted to isolate the effects on air quality due to meteorological conditions and long-term decreasing emission trends by comparing the PM 2.5 changes during lockdown to those before lockdown in 2020 and in previous years (2017–2019). The short-term premature mortality changes from both ambient and household PM 2.5 changes were quantified based on two recent epidemiological studies, with uncertainty of urban and rural population migration considerations. The national lockdown measures during COVID-19 led to a reduction of 5.1 µg m−3 in ambient PM 2.5 across the North China Plain (NCP) from January 25th to March 5th compared with the hypothetical simulation with no lockdown measures. However, a difference-to-difference method showed that the daily domain average PM 2.5 in the NCP decreased by 9.7 µg m−3 between lockdown periods before lockdown in 2020, while it decreased by 7.9 µg m−3 during the same periods for the previous three-year average from 2017 to 2019, demonstrating that lockdown measures may only have caused a 1.8 µg m−3 decrease in the NCP. We then found that the integrated population-weighted PM 2.5 , including both ambient and indoor PM 2.5 exposure, increased by 5.1 µg m−3 during the lockdown periods compared to the hypothetical scenario, leading to additional premature deaths of 609 (95% CI: 415–775) to 2,860 (95% CI: 1,436–4,273) in the short term, depending on the relative risk chosen from the epidemiological studies. Our study indicates that lockdown measures in China led to abrupt reductions in ambient PM 2.5 concentration but also led to significant increases in indoor PM 2.5 exposure due to confined indoor activities and increased usages of household fuel for cooking and heating. We estimated that hundreds of premature deaths were added as a combination of decreased ambient PM 2.5 and increased household PM 2.5. Our findings suggest that the reduction in ambient PM 2.5 was negated by increased exposure to household air pollution, resulting in an overall increase in integrated population weighted exposure. Although lockdown measures were instrumental in reducing the exposure to pollution concentration in cities, rural areas bore the brunt, mainly due to the use of dirty solid fuels, increased population density due to the large-scale migration of people from urban to rural areas during the Chinese New Year and long exposure time to HAP due to restrictions in outdoor movement. [ABSTRACT FROM AUTHOR]

Significant efforts have been directed toward addressing the adverse health effects of particulate matter, while few data exist to evaluate indoor exposure nationwide in China. This study aimed to investigate dwellings particulate matter levels in the twelve cities in China and provide large data support for policymakers to accelerate the legislative process. The current study was based on the CIEHS 2018 study and conducted in 12 cities of China. A total of 2128 air samples were collected from 610 residential households during the summer and winter. Both PM 10 and PM 2.5 were detected with a light-scattering dust meter in both the living room and bedroom. The Wilcoxon rank-sum test was performed to evaluate the correlations between PM 2.5 and PM 10 concentrations and both sampling season and site. Ratios of the living room to bedroom were calculated to evaluate the particulate matter variation between rooms. Hierarchical clustering was used to probe the question of whether the concentration varies between cities throughout China. The geometric means of the PM 2.5 in living rooms and bedrooms were 39.80 and 36.55 μg/m3 in the summer, and 70.97 and 67.99 μg/m3 in the winter, respectively. In the summer, approximately 70 % of indoor dwelling PM 2.5 exceeded the limit of 25 μg/m3, and for PM 10 approximately 60 % of dwellings demonstrated levels higher than 50 μg/m3; the corresponding values were over 90 % and 80 % in winter, respectively. In Shijiazhuang, Lanzhou, Luoyang and Qingdao, the geometric means of the PM 2.5 concentrations were observed to be 1.5 to 4.3 times higher during winter than during summer; similar concentrations in summer and winter were observed in Harbin, Wuxi, and Shenzhen, while the PM 2.5 concentrations in Panjin were approximately 1.5 times higher in summer than in winter. There was no significant difference in particulate matter concentrations between the living rooms and bedrooms. Scatter plots showed that cities with low GDP and a small population had higher concentrations, while Shenzhen, which has a higher GDP and a large permanent population, had a relatively low concentration of particulate matter. Our results suggest that indoor air pollution is a severe problem in China. It is necessary to continue monitoring indoor air quality to observe the changing trend under the tremendous effort of the Chinese government. • Indoor particulate matter exposure is prevalent in Chinese inhabitants. • In the winter, PM2.5 concentrations of Lanzhou and Mianyang were statistically higher than those of other cities. • Most of the cities air quality is better in the summer than in the winter, while the opposite result was observed in Panjin. [ABSTRACT FROM AUTHOR]

It is important to understand changes in PM 2.5 concentrations to evaluate and control air pollution in the classroom. In this paper, the PM 2.5 concentrations in classrooms of a primary school in North China were studied, where the particulate matter, temperature and humidity were monitored continuously from February 2018 to February 2019. Student behavior has been recognized as an important influential factor of indoor air quality; however, modeling the relationship between student behavior and PM 2.5 concentrations in classrooms remains an unsolved problem. In this paper, a novel intelligent data-driven symbolic regression method is applied to model the relationships between various factors and PM 2.5 concentrations. The advantage of this method is that it can automatically distill knowledge from data and discover the structures and parameters of relationship models simultaneously. By considering the annual schedules and daily behavior, a symbolic regression model is incorporated with mass conservation to describe the change in PM 2.5 concentrations caused by student behaviors. The experimental results show that outdoor PM 2.5 concentrations can influence the concentrations of indoor PM 2.5 through meteorological variations. Moreover, student behaviors play an important role and can lead to rapid changes in indoor PM 2.5 over a short timeframe. This paper provides a solid theoretical analysis of the relationship between indoor PM 2.5 concentrations and student behaviors in classrooms. The numerical models proposed by this research can assist in the analysis of PM 2.5 concentrations and the improvement of air quality in the classroom. • A student source strength model in the classroom is proposed by combining symbolic regression and conservation of mass. • PM2.5 concentrations in the classroom are affected by outdoor PM2.5, meteorological variations, and student behaviors. • A new method is proposed to calculate the changes of PM2.5 concentrations in the classroom. [ABSTRACT FROM AUTHOR]

• Two-year monitoring campaign of IEQ parameters of a nearly zero energy building was firstly presented in China. • The nearly zero energy building can provide the indoor with a comfortable thermal environment and good air quality with less energy demand. • The overheating problem in the whole year would be especially paid attention during design and operation. • The occupant behavior has a significant impact on energy consumption and thermal comfort. The paper presents a two-year field measurement and assessment of a nearly zero-energy Building in cold zones of China. These parameters of indoor environment quality (IEQ) and electricity consumption for HVAC are recorded. According to the measurement data, the most of indoor temperature was controlled in the range of 23 °C ~ 26 °C and relative humidity (RH) mainly fluctuates within the range of 30% ~ 60%. The concentrations of carbon dioxide (CO 2) and particulate matter (PM 2.5) are lower than the relevant standard requirements in most of the time. The average electricity consumption for HVAC was 33.05kWh/(m2·a) and the heating and cooling demands could be reduced by 55.2% and 54.0%, respectively, compared with existing buildings. In general, the NZEB can provide indoor comfortable thermal environment and indoor air quality with less energy demand, but the overheating problem in summer and effect of occupant behavior should be especially paid attention during operation. Overall, the experience from the actual operation of NZEBs will help China to reach its goals of reducing carbon emissions and addressing climate change through realizing the energy-saving potential of NZEBs. [ABSTRACT FROM AUTHOR]