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Volatile organic compounds (VOCs) are major chemical pollutants in indoor air. Indoor fabrics, such as curtains, carpets, sofas, and clothes, strongly adsorb VOCs due to their high loading rates and large specific surface areas. The desorption of VOCs from these fabrics can act as a secondary source, worsening indoor air pollution and prolonging its effects. The diffusion coefficient is a key parameter that determines the source-sink properties of fabrics. In this study, the VOC diffusion characteristics in fabrics were investigated through microstructural examination, mass transfer analysis, and environmental chamber experiments. Yarn and fiber gaps were identified as dual mass transfer channels within the fabrics and were represented using two distinct fractal models. A dual-porosity medium (DPM) model, based on these fractal representations, was developed to predict the VOC diffusion coefficients in indoor fabrics and was validated via experiments under various environmental conditions and fabric-VOC combinations. The results highlight the significant impact of fabric structure and composition on VOC adsorption and emission dynamics. The validated DPM model provides a comprehensive approach to predicting VOC diffusion in fabrics, providing a more accurate method for assessing indoor air quality and fabric-mediated human exposure. [Display omitted] • Indoor fabrics act as both sources and sinks for VOC transport. • Yarn and fiber gaps are identified as key diffusion channels in fabrics. • A fractal-based DPM model is developed for VOC diffusion in fabrics. • Experiments and model comparisons confirm the reliability of the DPM model. [ABSTRACT FROM AUTHOR]

Volatile organic compounds (VOCs) emitted from decorative building materials are the main source of indoor air pollution, which endangers human health. Source control is the most direct method to reduce the amount of harmful substances emitted from a material. In view of the excellent adsorption performance and effective fixation of the adsorbent on VOC molecules, small amounts of adsorbents can be blended into the raw materials used in the production of building materials, which results in the manufacture of modified building materials with low VOC emissions. According to the type and ratio of additional adsorbents, the VOC emission characteristics of the modified building materials vary. Based on the analysis of the multi-component and multi-scale mass transfer mechanism, a prediction system for the VOC emission characteristics of modified building materials was proposed. Four types of adsorbents, namely, wood-based activated carbon (WAC), shell activated carbon (SAC), coconut shell activated carbon (CSAC), and potassium permanganate impregnated alumina (PIA) were used to manufacture the modified medium density fiberboards. Moreover, pore structure characterization tests and environmental chamber tests were conducted to verify the accuracy of the theoretical prediction system. The results revealed that an absorbent with a high partition coefficient has a more significant source suppression effect. The proposed VOC emission characteristic prediction system for modified building materials can optimize the type and ratio of adsorbents for engineering applications and therefore, provide a basis for the selection of effective VOC source control strategies. • Modelling VOC emission characteristic parameters of modified building materials. • Manufacture of modified MDFs blended with four types of adsorbents, respectively. • The reliability of the prediction models is well verified by experiments. • It is significant for the guidance on designing low-emission building materials. [ABSTRACT FROM AUTHOR]

Abstract Formaldehyde emissions of building materials are greatly influenced by the indoor air temperature. An accurate evaluation of the influence of formaldehyde emissions on indoor air quality requires an investigation of the emission characteristic parameters at different temperatures. Based on the adsorption potential theory, this paper derived the correlation between the initial emittable concentration (C 0) and the partition coefficient (K) of formaldehyde emissions from building materials. On account of the characteristics of a high equilibrium concentration of formaldehyde emissions under high temperatures in an airtight environment, a step temperature rising emission (STRE) method to simultaneously determine the characteristic parameters of formaldehyde emissions at multiple temperatures was proposed. This innovative method was validated by theoretical models in the literature and via independent experiments. In addition, an optimization method for determining the appropriate volumetric air/material phase ratio was discussed and analyzed to improve the accuracy and reliability of the STRE method. This method aims to improve the measurement efficiency of the emission characteristic parameters and provides inspiration for evaluating the hazard posed by formaldehyde emissions from furniture and building materials. Graphical abstract Image 1 Highlights • The correlation between C 0 and K is derived based on adsorption potential theory. • The STRE method is proposed to efficiently determine the characteristic parameters. • Hazard of formaldehyde emissions at multiple temperatures can be quick predicted. • The reliability of the STRE method is comprehensively verified. [ABSTRACT FROM AUTHOR]

Abstract: This paper employs the state space method to characterize transportation of indoor gaseous pollutant in steady airflow field. From the differential equations governing contaminant transportation in space, the state space equation for transportation is proposed and the analytical solution is obtained. In the method, the matrix covering hologram of the transportation is derived. The state space equation is validated with the analytic solution for the case of the simultaneous transportation of the pollution for piston flow. Similarly, the concentration from the proposed method for a 2-D case also agrees well with the result from CFD method based on the experimentally validated flow field. Based upon the analytic solution of the state equation, it is easily known that the influence of the initial concentration distribution and the pollution source on the concentration at the specific point. In addition, assisted by Chen’s zero equation turbulence model , the concentration field for a 3-D case is simulated by the presented method. It is found that there exists a regular stage at which the relative effect of the initial concentration distribution and the source on the concentration field will not change with time. [Copyright &y& Elsevier]

Abstract: There are many mass-transfer models for predicting VOC emissions from building materials described in the literature. In these models, the volatile organic compound (VOC) emission rate and its concentration in a chamber or a room are usually obtained by analytical method or numerical method. Although these methods demonstrate some salient features, they also have some flaws, e.g., for analytical method the solutions of both room or chamber VOC concentration and building material VOC emission rate are constituted of the sum of an infinite series, in which additional computation for finding roots to a transcendental function is necessary, but sometimes quite complicated. Besides, when it is applied in complex cases such as multilayer emission with internal reaction, the solution is very difficult to get; for conventional numerical methods such as finite difference method, discrete treatment of both time and space may cause calculation errors. Considering that, the state-space method widely used in modern automation control field and the heat transfer field is applied to simulate VOC emissions from building materials. It assumes that a slab of building material is composed of a number of finite layers, in each of which the instantaneous VOC concentration is homogenous during the entire process of emission, while the time is kept continuous. Based on this assumption we can predict both the VOC emissions rate and the concentrations of VOCs in the air of a chamber or room. The method is generally applied to simulate VOC emissions from arbitrary layers of building materials, and the solution is explicit and simple. What''s more, the method can be applied to the cases where a reaction producing/removing VOC in building materials exists. For some specific cases the method is validated using the experimental data and the analytical solutions in the literature. The method provides a simple but powerful tool for simulating VOC emissions from building materials, which is especially useful in developing indoor air quality (IAQ) simulation software. [Copyright &y& Elsevier]

A correlation between partition coefficients, K, of dry building material and liquid molar volume of volatile organic compounds (VOCs) in it, v l, is presented. Experiment for determining the partition coefficients of the target VOCs including benzene, toluene, ethylbenzene for two kinds of building materials was conducted by a method developed by us. The experimental data verified the correlation. Also the correlation was supported well by the experimental data in the literature. It is found that the correlation can predict the partition coefficients of VOCs with similar structure in the same building material. [Copyright &y& Elsevier]

Abstract: To analyze the thermal performance and indoor air quality (IAQ) in building simultaneously and quickly, we have developed an integrated modeling tool to simulate the dynamic indoor multi-parameters distributions and concentrations. The tool can take the parameters including indoor temperature, indoor humidity, and pollutant concentrations (e.g., volatile organic compounds (VOC) CO2, particulate matter (PM)), as well as the heating/cooling load of heating, ventilating, and air-conditioning (HVAC) system into account. It couples a new zonal approach based on room air age. This paper presents the basic concept and flow chart in developing the modeling tool, and demonstrates the tool''s application in a hypothetical health care building. The tool could be used for design of HVAC system with IAQ control devices and for the simultaneous analysis of thermal performance and IAQ in buildings. [Copyright &y& Elsevier]

The volatile organic compound (VOC) emissions of building materials are represented by three parameters: the initial emittable concentration (C 0), diffusion coefficient (D), and partition coefficient (K). Accurate measurement of these three parameters is key to the reasonable prediction and control of VOC emissions from building materials. In this study, a single airtight emission (SAE) method for determining the three emission parameters of building materials is proposed. Based on the dynamic analysis of the normalized relative sensitivity coefficient of the characteristic parameters in an airtight environment, the three parameters could be determined by piece-wise fitting of the experimental data. This method requires only a single airtight emission experiment for building materials, and the experimental time is short (≤36 h). C 0 , D , and K can be simply calculated by nonlinearly fitting of the experimental data. It demonstrated some significant improvements towards better simplicity and accuracy compared to previous methods. The emission parameters of formaldehyde in the four types of building materials were determined following the SAE method, and the predicted values agreed well with the experimental values under various environmental conditions. Additionally, the possible sources of errors using this method were analyzed, and the influence of the initial hypothesis on the results was also discussed to further verify the feasibility and accuracy of the method. The SAE method proposed in this study can efficiently and accurately measure the formaldehyde emission parameters of building materials, and is suitable for application in engineering, requiring a short time and simple operation. [Display omitted] • A SAE method for measuring the emission parameters of building materials is proposed. • The experimental data is piece-wise fitted based on the sensitivity analysis. • The influence of initial hypothesis on the prediction results is analyzed. • SAE method has high precision and is suitable for application in engineering. [ABSTRACT FROM AUTHOR]

Volatile organic compound (VOC) emissions from coating materials, such as paint, can result in poor indoor air quality (IAQ). In this study, a fundamental mathematical model for VOC emissions from paint film was established based on the mass transfer mechanism. In this model, mass transfers in the air, at the air–paint interface, in the paint film, at the paint–substrate interface, and in the porous substrate are mathematically described. Three statuses of the paint film including wet, semi-dry, and dry were defined quantitatively by the saturation of VOC liquid in the pores of the paint film. Therefore, the entire process from the wet to dry stages of VOC emission from the material can be characterized by the new model. In addition, the model was validated using experimental data in the literatures. A case study revealed that the effects of indoor environmental parameters on VOC emission of paint film change with the stages of the paint film. The film thickness and the porosity of the substrate have more significant effects on the emission of the paint film in the semi-dry and dry stages, respectively. This analysis can provide environmental control strategies and material selection schemes for promoting good IAQ. • A mathematical model is proposed to characterize the VOC emissions from paint film. • Three statuses of the paint film from wet to dry are defined quantitatively. • VOC emission characteristics of different drying stages can be depicted accurately. • The influence factors of VOC emissions from paint film are analyzed. [ABSTRACT FROM AUTHOR]

Semivolatile organic compounds (SVOCs) are highly susceptible to sorption by particles, so the presence of particles will have a significant impact on indoor SVOC distribution. The partition coefficient of SVOCs between the air and particles was closely related to indoor environmental parameters, particle composition, and physical structure. However, owing to the complexity of indoor particle composition and the variety of SVOCs, theoretical models of the particle partition coefficient are still not comprehensive in characterizing the SVOC sorption process by different components, and most only consider the sorption of elemental carbon and organic carbon. Studies have demonstrated that inorganic particles have nonnegligible sorption capacity on SVOCs. In this study, experimental results in the literature were compared with the theoretical values predicted by the widely used equilibrium model of the SVOC particle/gas partition coefficient. It was found that neglecting the inorganic components in particles led to a low predictive value of the partition coefficient. Therefore, based on the two-parameter equilibrium model, a novel model considering the sorption of SVOCs on inorganic substances was proposed. This model could describe the formation mechanism of the particle/air partition coefficient more comprehensively, and the experimental data in many relevant studies were used to verify the model. In addition, based on this model, the quantitative relationship between particle property and its sorption of SVOCs was calculated and analyzed. This study aimed to improve the predictive accuracy of indoor SVOC concentrations and help to make more accurate estimates of the risk of human health exposure in further research. • Sorption of SVOCs by inorganic components in particles cannot be neglected. • An improved model of the SVOC particle/gas partition coefficient was proposed. • The accuracy of the improved model was comprehensively verified by literature data. • The correlation between particle property and partition coefficient was analyzed. [ABSTRACT FROM AUTHOR]

Phthalates (PAEs) are a group of typical semivolatile organic compounds that are widely present in indoor environments with multiple phases. Indoor air, airborne particle and settled dust are considered to be typical indicators of PAE contamination as well as media of human exposure, and the interactions between them are complex. Among various phthalate compounds, di 2-ethylhexyl phthalate (DEHP) was identified as the predominant individual phthalate in settled dust. The existing DEHP contamination assessment requires multiphase sampling or solving the dynamic mass transfer models with multiple partial differential equations, which are both complicated and time-consuming. This study investigated the influence of the indoor source loading rate, surface type, particle size and cleaning frequency on the partitioning between the settled dust-phase, airborne particle-phase and gas-phase. The concentration correlations of DEHP between multiphases were consequently derived, which balance accuracy and complexity well. By comparison with field sampling data in the literatures, the rationality and accuracy of the concentration correlations were validated. Based on the concentration correlations, a new method of directly using dust-phase concentration to estimate the non-dietary exposure to DEHP was proposed. The results indicated that ingestion of settled dust contributes the most to non-dietary exposure. Special attention should be given to infants and toddlers, who suffer the highest daily exposure to DEHP among all age groups. This study provides a new and efficient solution for estimating indoor DEHP pollution loads conveniently and rapidly, offering valuable insights for future research in this field. [Display omitted] • Settled dust can be regarded as the passive sampling medium of DEHP. • The concentration correlations between multi-phase DEHP were derived. • Non-dietary exposure was assessed using the dust-phase concentration. • This study provides an efficient solution for estimating indoor DEHP contamination. [ABSTRACT FROM AUTHOR]

The diffusion coefficient, D, partition coefficient, K, and the initial volatile organic compounds (VOCs) in dry building materials, are the three key parameters used to predict the VOC emissions. D and K may be strongly affected by temperature. We have developed a new and simple method, the C-history method, to measure the diffusion coefficient, D and the partition coefficient, K of formaldehyde in dry building materials at temperatures of 18, 30, 40 and 50°C. The measured variations of the diffusion coefficients and the partition coefficients with temperature for particle board, vinyl floor, medium-and high-density board are presented. A formula relating the partition coefficient and related factors is obtained through analysis. This formula can predict the partition coefficient in principle and provide an insight for fitting experimental data, and it agrees well with the experimental results. [Copyright &y& Elsevier]

Porous fabrics have a significant impact on indoor air quality by adsorbing and emitting chemical substances, such as volatile organic compounds (VOCs) and semi-volatile organic compounds (SVOCs). Understanding the partition behavior between organic compound molecules and indoor fabrics is crucial for assessing their environmental fate and associated human exposure. The physicochemical properties of fabrics and compounds are fundamental in determining the free energy of partitioning. Moreover, environmental factors like temperature and humidity critically affect the partition process by modifying the thermal and moisture conditions of the fabric. However, existing methods for determining the fabric-air partition coefficient are limited to specific fabric-chemical combinations and lack a comprehensive consideration of indoor environmental factors. In this study, large amounts of experimental data on fabric-air partition coefficients (K fa) of (S)VOCs were collected for silk, polyester, and cotton fabrics. Key molecular descriptors were identified, integrating the influences of physicochemical properties, temperature, and humidity. Subsequently, two typical quantitative structure-property relationship (QSPR) models were developed to correlate the K fa values with the molecular descriptors. The fitting performance, robustness, and predictive ability of the two QSPR models were evaluated through statistical analysis and internal/external validation. This research provides insights for the high-throughput prediction of the environmental behaviors of indoor organic compounds. Among various indoor surfaces, porous fabrics serve as the primary medium for the migration, distribution, and fate of chemicals, owing to their high loading rate and large specific surface area. Understanding the partition behavior of organic compounds between fabric and air is essential. However, existing methods are often restricted to specific fabric-chemical combinations and lack a comprehensive consideration of indoor environmental factors. This study introduces a QSPR modeling approach with broad applicability, effectively predicting the fabric-air partition coefficients of (S)VOCs, and incorporating the effects of ambient temperature and humidity. It enables high-throughput assessment of indoor chemical pollution and human exposure. [Display omitted] • QSPR modeling was used to predict fabric-air partition coefficients for (S)VOCs. • Key molecular and environmental descriptors were identified and integrated. • Two advanced and well validated models were proposed for different scenarios. • Study facilitates high-throughput assessment of chemical fate and human exposure. [ABSTRACT FROM AUTHOR]

Fabrics are widely distributed in residential buildings. Due to their highly porous structures and large specific surface areas, they have strong adsorption properties for volatile organic compounds (VOCs). The secondary source effect that is induced by their desorption can aggravate indoor air pollution and prolong the pollution period. The partition coefficient, which is a characteristic parameter of VOC mass transfer, is sensitive to variations in environmental parameters. However, due to the inherent differences between fabrics and other indoor porous building materials, the relevant research conclusions on the VOC mass transfer parameters of building materials cannot be applied. In addition, the effects of temperature and humidity on the partitioning behavior of VOCs on fabrics have rarely been quantitatively analyzed. Based on an analysis of the porous structure and corresponding mass transfer process of fabrics, a novel prediction model of the fabric partition coefficient under the coupling effect of temperature and humidity is proposed. Three types of indoor typical fabrics and primary water-soluble VOC (formaldehyde) and water-insoluble VOC (benzene, toluene) are examined experimentally via hygroscopicity tests and environmental chamber tests. The experimental results demonstrate the reliability of the proposed model for a variety of conditions. [Display omitted] • A mathematical model is proposed to characterize the K of indoor fabrics. • The coupling effect of temperature and humidity on K is quantitatively analyzed. • Partition of formaldehyde, benzene and toluene on three types of fabrics is measured. • The reliability of the model is comprehensively verified under various conditions. [ABSTRACT FROM AUTHOR]

Phthalate esters (PAEs) are ubiquitous and among the most abundant semi-volatile organic compounds (SVOCs) in indoor environments. Due to their low saturated vapor pressure, SVOCs tend to adhere to indoor surfaces and particulate matters, which may result in higher total concentrations than occur in the gas phase alone. Thus, gas/particle partitioning of PAEs plays an important role in their indoor fates and health risks. However, the influence of indoor environmental parameters, including temperature and humidity, on the partitioning of PAEs between air and particles is rarely known. In this study, a novel experimental system was designed to investigate the effects of temperature and humidity on partitioning behavior between gas- and particle-phase PAEs. The chamber experiments were conducted at temperatures of 12.5 °C, 17.5 °C, 24.0 °C, 29.5 °C and 40.0 °C and moisture contents of 3.5 g/kg, 5.0 g/kg, 6.5 g/kg, 8.0 g/kg and 9.5 g/kg dry air. The results showed that higher temperatures led to stronger emission of phthalate esters from the PVC panel, which resulted in higher gas-phase concentrations of phthalate esters and particle-phase concentrations. In addition, temperature has a strong negative effect on the gas/particle partition coefficient (K p), and an order of magnitude difference in K p was observed between 12.5 and 40 °C. There are exponential decay laws between K p and the absolute temperature. However, a smaller effect of humidity than of temperature on K p was revealed, and no obvious law was found. Moreover, K p of compounds with larger molecular weights are more obviously influenced by the variations in environmental factors. This study is of positive significance for reducing the health risks of PAEs by guiding the regulation of indoor environmental parameters. Image 1 [ABSTRACT FROM AUTHOR]