Initial Emittable Concentration Research Articles

Study on the effect of humidity on formaldehyde emission parameters of wood-based panels

Wood-based panels are a significant source of indoor volatile organic compounds (VOCs), crucial for managing indoor pollution. The emissions from wood-based panels are influenced by both intrinsic factors, including their composition and manufacturing process, and extrinsic environmental conditions, such as temperature and humidity. In this paper, the emission of formaldehyde in plywood was studied under different temperature conditions (15°C, 23°C, 32°C and 37°C) and different humidity conditions (40%, 60% and 80%) by environmental chamber method. To understand the influence of relative humidity on the key parameters of panels from a mechanism perspective, this paper investigates the influence of relative humidity on the initial emittable concentration of formaldehyde, based on the hydrolysis reaction of urea-formaldehyde resin. Concurrently, the molecular dynamics and porous panels model were amalgamated to assess the influence of relative humidity on both the partition and diffusion coefficient. To simulate the emission process in a real environment, a control equation that allows for variations in both temperature and humidity is needed. This paper employs the method of variable separation to derive a simplified control equation. Subsequently, experimental data was utilized to validate the derived equation’s effectiveness within the practical indoor environmental range.

Measurement methods and impact factors for the key parameters of VOC/SVOC emissions from materials in indoor and vehicular environments: A review.

The emissions of volatile organic compounds (VOCs) and semi-volatile organic compounds (SVOCs) from indoor building and vehicle cabin materials can adversely affect human health. Many mechanistic models to predict the VOC/SVOC emission characteristics have been proposed. Nowadays, the main obstacle to accurate model prediction is the availability and reliability of the physical parameters used in the model, such as the initial emittable concentration, the diffusion coefficient, the partition coefficient, and the gas-phase SVOC concentration adjacent to the material surface. The purpose of this work is to review the existing methods for measuring the key parameters of VOCs/SVOCs from materials in both indoor and vehicular environments. The pros and cons of these methods are analyzed, and the available datasets found in the literature are summarized. Some methods can determine one single key parameter, while other methods can determine two or three key parameters simultaneously. The impacts of multiple factors (temperature, relative humidity, loading ratio, and air change rate) on VOC/SVOC emission behaviors are discussed. The existing measurement methods span very large spatial and time scales: the spatial scale varies from micro to macro dimensions; and the time scale in chamber tests varies from several hours to one month for VOCs, and may even span years for SVOCs. Based on the key parameters, a pre-assessment approach for indoor and vehicular air quality is introduced in this review. The approach uses the key parameters for different material combinations to pre-assess the VOC/SVOC concentrations or human exposure levels during the design stage of buildings or vehicles, which can assist designers to select appropriate materials and achieve effective source control.

Characterizing the emission behaviors of cumulative VOCs from automotive solvent-based paint sludge.

Volatile organic compounds (VOCs) diffused from paint sludge are potential hazard contributing significantly to environmental pollution and exposure to them can cause severe health issues. In this paper, a diffusion-controlled model was firstly developed for characterizing the emission behaviors of cumulative VOCs from automotive solvent-based paint sludge based on the worst field management scenario. The presented model is characterized by two key parameters: the diffusion coefficient (Dm) and the initial emittable concentration (Cm,0), which can be simultaneously obtained by our proposed ER-history method. Four major components were detected including 1-butanol, butyl acetate and 1,2,4-trimethylbenzene and 1-ethyl-4-methylbenzene. In addition, the model was validated by using environmental data in a ventilated test chamber, proving that the model is reliable and convincing. However, relative deviations of 1-butanol and butyl acetate are larger than those of 1,2,4-trimethylbenzene and 1-ethyl-4-methylbenzene, indicating that the model is more accurate for predicting hydrophobic VOCs release than those of hydrophilic VOCs. Besides, an increase in Cm,0 and Dm tends to enhance VOCs cumulation release. Our studies provide new insight into experimental designs for rapid model parameters measurement and a sound basis for estimating VOCs cumulative release from paint sludge as well as for hazardous waste.

A rapid and robust method to determine the key parameters of formaldehyde emissions from building and vehicle cabin materials: Principle, multi-source application and exposure assessment

The ubiquity of formaldehyde emitted in indoor and in-cabin environments can adversely affect health. This study proposes a novel full-range C-history method to rapidly, accurately and simultaneously determine the three key parameters (initial emittable concentration, partition coefficient, diffusion coefficient) that characterize the emission behaviors of formaldehyde from indoor building and vehicle cabin materials, by means of hybrid optimization. The key parameters of formaldehyde emissions from six building materials and five vehicle cabin materials at various temperatures, were determined. Independent experiments and sensitivity analysis verify the effectiveness and robustness of the method. We also demonstrate that the determined key parameters can be used for predicting multi-source emissions from different material combinations that are widely encountered in realistic indoor and in-cabin environments. Furthermore, based on a constructed vehicle cabin and the determined key parameters, we make a first attempt to estimate the human carcinogenic potential (HCP) of formaldehyde for taxi drivers and passengers at two temperatures (25 °C, 34 °C). The HCP for taxi drivers at both temperatures exceeds 10−6 cases, indicating relatively high potential risk. This study should be helpful for pre-evaluation of indoor and in-cabin air quality, and can assist designers in selecting appropriate materials to achieve effective source control.

Predicting the emissions of VOCs/SVOCs in source and sink materials: Development of analytical model and determination of the key parameters.

The emissions of volatile organic compounds (VOCs) and semi-volatile organic compounds (SVOCs) from indoor materials pose an adverse effect on people's health. In this study, a new analytical model was developed to simulate the emission behaviors for both VOCs and SVOCs under ventilated conditions. Based on this model, we further introduced a hybrid optimization method to accurately determine the key parameters in the model: the initial emittable concentration, the diffusion coefficient, the material/air partition coefficient, and the chamber surface/air partition coefficient (for SVOCs). Experiments for VOC emissions from solid wood furniture were performed to determine the key parameters. We also evaluated the hybrid optimization method with the data of flame retardant emissions from polyisocyanurate rigid foam and VOC emissions from a panel furniture in the literature. The correlation coefficients are high during the fitting process (R2=0.92-0.99), demonstrating effectiveness of this method. In addition, we observed that chemical properties could transfer from SVOC-type to VOC-type with the increase of temperature. The transition temperatures from SVOC-type to VOC-type for the emissions of tris(2-chloroethyl) phosphate (TCEP) and tris(1-chloro-2-propyl) phosphate (TCIPP) were determined to be about 45 ℃ and 35 ℃, respectively. The present study provides a unified modelling and methodology analysis for both VOCs and SVOCs, which should be very useful for source/sink characterization and control.

Determination of the key parameters of VOCs emitted from multi-layer leather furniture using a region traversal approach

Volatile organic compounds (VOCs) emitted from indoor materials and products are one of the main factors affecting air quality and human health. Compared with building materials and wooden furniture, leather furniture has a more complex internal structure and uneven emission surfaces. The market share of leather furniture is relatively high, while investigation on this kind of furniture is relatively rare. In this study, we develop a region traversal method to measure the three key parameters of VOC emissions from typical two-layer leather furniture, i.e., the initial emittable concentration, the diffusion coefficient, and the partition coefficient. A series of experiments examining VOC emissions from a leather sofa under different conditions, were carried out in a 1 m3 chamber. This method locks the upper and lower limits of an optimal solution through loop calculation in parameter intervals, and demonstrates high accuracy, efficiency and robustness. The good agreement (R2 > 0.95) between model predictions and experimental data confirms the reliability of this method. In addition, the influence of temperature and air exchange rate on the key parameters is explored. Results indicate that, increasing the temperature leads to an increase in Dm and a decrease in K, and that air exchange rate does not affect the key parameters, which is consistent with physical principles. The region traversal method is further applied to analyze the emission scenarios for other furniture, which is very helpful for indoor air quality pre-evaluation.

A new method for determining the formaldehyde emission characteristic parameters of building materials: Single airtight emission method

The volatile organic compound (VOC) emissions of building materials are represented by three parameters: the initial emittable concentration (C0), 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). C0, 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.

VOC emissions from two-layer building and vehicle cabin materials: Measurements and independent validation

Most indoor building materials and vehicle cabin materials consist of multiple layers which can emit volatile organic compounds (VOCs), and these adversely affect indoor and in-cabin air quality. Previous studies have generally targeted VOC emissions from single-layer materials, while only a few look at emissions from multi-layer products, with experimental studies being very rare. This paper uses a two-layer emission model to predict the emission characteristics of VOCs from both indoor building materials and vehicle cabin materials. A hybrid optimization approach (ant colony optimization (ACO) coupled particle swarm optimization (PSO)) is presented to determine the three key parameters for each layer of material in the model, i.e., the initial emittable concentration, the diffusion coefficient, and the partition coefficient. The results indicate that this method has significant advantages compared with previous fitting methods. In addition, independent experiments for formaldehyde emission from a variety of two-layer building materials, and acetaldehyde emission from car seat materials, were performed to validate the two-layer emission model. The good agreement between model predictions and experimental results implies that the key parameters derived for each layer of material can be applied in two-layer emission scenarios. Furthermore, we explore the influence of the three key parameters on VOC emission behaviors, which is helpful for achieving effective source control.

Measurement of the key parameters of VOC emissions from wooden furniture, and the impact of temperature

Volatile organic compounds (VOCs) emitted from furniture severely influence indoor air quality. Prior studies have mainly focused on the emissions from building materials and vehicle cabin materials, but rarely refer to indoor furniture. Considering the complex internal structure of furniture, this study presents a two-layer numerical model to describe the emission behaviors of VOCs from wooden furniture. A multi-parameter regression method was then proposed to determine the key parameters in the furniture, i.e., the initial emittable concentration, the diffusion coefficient and the partition coefficient. Experiments were conducted in a 1 m3 environmental chamber for VOC emissions from two kinds of wooden furniture (panel furniture and solid wood furniture). The agreement between model predictions and test data (R2 = 0.97–0.99) demonstrated the effectiveness of the model and measured key parameters. Compared with the traditional single-layer model, the two-layer numerical model can characterize the whole emission process from furniture better. In addition, the impact of temperature on the key parameters for furniture emissions was explored. With an increase in temperature from 23 °C to 35 °C, the diffusion coefficients for different VOCs from different wooden furniture, increase by 200%–2993%, while partition coefficients decrease by 41%–94%. This pattern conforms with that of VOC emissions from building materials. The present study should be helpful for source characterization of furniture and the associated exposure assessment.

Influence of temperature on formaldehyde emission parameters of solvent-based coatings

Temperature affects the emission behavior of formaldehyde from coatings. Initial emittable concentration (C0), diffusion coefficient (Dm) and partition coefficient (K) are three key parameters for characterizing the formaldehyde emission from coatings. However, recent research concerning temperature effect on volatile organic compound (VOC) emission from coatings mainly focused on the influence on gas-phase concentration or emission rate, and few studies were conducted on the correlation between temperature and key emission factors (C0, Dm and K). In this work, formaldehyde emission from a solvent-based coating was measured at 10, 15, 20 and 25°C in a 30 L environmental chamber. From 10 to 25°C, C0 increased by 2.35-fold, and positive linear correlation was observed between ln(C0*T0.5) and 1/T. An empirical equation characterizing temperature effect on K was derived. Temperature effects on Dm were negligible. Through the obtained equations that can characterize the correlation between temperature and the key parameters, C0 and K at different temperatures from this work can be easily calculated. This study would be useful for predicting emission behavior of formaldehyde from solvent-based coatings and better understanding the influence of temperature.

Predicting the emission characteristics of VOCs in a simulated vehicle cabin environment based on small-scale chamber tests: Parameter determination and validation

Volatile organic compounds (VOCs) emitted from vehicle parts and interior materials can seriously affect in-cabin air quality. Prior studies mainly focused on indoor material emissions, while studies of emissions in-cabins were relatively scarce. The emission behaviors of VOCs from vehicle cabin materials can be characterized by three key emission parameters: the initial emittable concentration (C0), diffusion coefficient (Dm), and partition coefficient (K). Based on a C-history method, we have performed a series of tests with a 30 L small-scale chamber to determine these three key emission parameters for six VOCs, benzene, toluene, ethylbenzene, xylene, formaldehyde, and acetaldehyde, from typical vehicle cabin materials, car roof upholstery, carpet, and seat. We found that acetaldehyde had the highest level in the gas-phase concentration and C0, which differs from residential indoor environments where formaldehyde is usually the most prevalent pollutant. The influence of temperature on the key emission parameters was also investigated. When the temperature rose from 25 °C to 65 °C, C0 increased by 40–640%, Dm increased by 40–170%, but K decreased by 38–71% for different material-VOC combinations. We then performed an independent validation to demonstrate the accuracy of the measured key emission parameters. Furthermore, considering that in reality, several materials coexist in vehicle cabins, we made a first attempt at applying a multi-source model to predict VOC emission behaviors in a simulated 3 m3 vehicle cabin, using the key emission parameters obtained from the small-scale chamber tests. The good agreement between the predictions and experiments (R2 = 0.82–0.99) demonstrated that the three key emission parameters measured via chamber tests can be scaled to estimate emission scenarios in realistic vehicle cabin environments. A pollution contribution analysis for the tested materials indicated that the car seat could significantly contribute to the total emissions.

A general regression method for accurately determining the key parameters of VOC emissions from building materials/furniture in a ventilated chamber

Abstract Emissions of volatile organic compounds (VOCs) from building materials/furniture can be characterized by three key parameters: the initial emittable concentration (C0), the diffusion coefficient (Dm), and the partition coefficient (K). These parameters provide the basis for realizing effective source control, as well as for evaluating health risks. In this study, we propose a general regression method to accurately and rapidly measure the three key parameters of VOC emissions from building materials/furniture in a ventilated chamber. This method firstly establishes the relationship between the three key parameters and the first root of the analytical solution describing VOC emissions, and this root is then determined by curve regression. Compared with previous regression methods which need to fit two or three parameters simultaneously, the main merit of the present method lies in that it just needs to fit one parameter and thus can get a unique solution. We tested panel furniture in a ventilated chamber to measure the three key parameters of some common VOCs. Results indicate that the model predictions based on the parameters determined via this new method agree well with experimental data, which validates the reliability of this proposed method. Analyzing data from the literature further demonstrates the accuracy of this method. The present method involves chamber testing under ventilated conditions only, which is consistent with the testing conditions for many standards, thus will benefit routine laboratory testing.

Assessment of an experimental method for determining the three key parameters of VOC emissions from solid materials

The VOC emission processes from a solid material can be described by three key parameters: the partition coefficient (K), the initial emittable concentration (C0) and, the diffusion coefficient (D). These emission key parameters need to be determined experimentally for a VOC-material pair. A new method from literature allows determining simultaneously the three emission key parameters. However, this method has been evaluated in a single experiment only for formaldehyde. Therefore, the purpose of this study is to assess the efficiency and the reproducibility of the experimental method from literature performing three tests in the same experimental conditions. This work permits to determine the three key parameters of eight main VOC emitted from a particleboard and to evaluate the accuracy of the experimental method. Successfully, experiments carried out using a 128 L well-mixed chamber containing a particleboard, and connected to an online gas analyzer (Selected Ion Flow Tube-Mass Spectrometry), allow the effective characterization of the source material. Results evidence that compared to other VOCs, formaldehyde shows a specific behaviour: the response of formaldehyde between airtight and ventilated regimes is highly contrasted with those of other emitted VOCs.

An improved mechanism-based model for predicting the long-term formaldehyde emissions from composite wood products with exposed edges and seams

Emissions of formaldehyde from building materials and furniture can cause adverse health effects. Traditional models generally only consider emissions as a physical process that can be characterized by three key parameters: the initial emittable concentration, the diffusion coefficient and the partition coefficient. However, the physical-based model causes discrepancy in predicting long-term formaldehyde emissions for the cases where chemical reaction (i.e., hydrolysis) occurs over time. In this study, an improved mechanism-based model was developed by combining the chemical reaction process with a physical mass transfer process to more accurately predict the long-term emission behaviors. The chamber testing data of formaldehyde emissions from exposed edges and seams of a laminate flooring product made with composite wood core for about 1.5 year was used to validate the model. Results indicate that the mechanism-based model characterizes well the long-term formaldehyde emissions from the tested material. Predictions of different models further demonstrate the advantages of this improved model compared with the physical model or with empirical models. This study is the first attempt to check the feasibility of including the chemical reaction term in emission modeling and to quantitatively explore the importance of its contribution to long-term formaldehyde emissions, which includes most of the indoor emissions from materials and furniture.

Characterization of VOC emissions from composite wood furniture: Parameter determination and simplified model

The emissions of volatile organic compounds (VOCs) from furniture contribute significantly to indoor air pollution. The majority of studies focus on the emission behaviors of building materials, and seldom consider furniture. This study develops a novel prediction-correction method to determine the three key parameters characterizing VOC emissions from furniture: the initial emittable concentration, the diffusion coefficient, and the partition coefficient. In addition, a simplified model is proposed to simulate the VOC emission behaviors, which owns the merits of simple form and high accuracy. Experiments investigating VOC emissions from two kinds of composite wood furniture under ventilated conditions were conducted to determine the key parameters. The calculated gas-phase concentrations based on these parameters and the simplified model agree well with experimental data from the ventilated chamber, demonstrating the effectiveness of the proposed measurement method and the simplified model. The application range of the model is then obtained through dimensionless analysis, and the model is further extended to evaluate VOC emissions for other loading ratios. This study is the first attempt to simultaneously and rapidly measure the three key parameters for furniture-VOC combinations under ventilated conditions, and should be helpful for enriching the database, and for the rapid screening of VOC emissions from furniture.

A novel method to determine the formaldehyde emission characteristic parameters of building materials at multiple temperatures

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 (C0) 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.

Estimates of parameters for formaldehyde emission model from plywood panel under various temperature and relative humidity conditions

The initial emittable concentration, Cm,0, the material phase diffusion coefficient, Dm, and the air/material partition coefficient, K, are the key parameters used to predict the formaldehyde emissions from indoor building materials. This work presents formaldehyde emission experiments of plywood panels in a climatic chamber under various environmental conditions, which provides information on how relative humidity, temperature, and loading degree affect the formaldehyde emission. The experimental results showed that formaldehyde concentration in the climatic chamber increased rapidly during the initial 3 h, and then reached equilibrium after 7 h. The equilibrium concentration of formaldehyde in the closed chamber was increased by 1.1–1.3 times with the relative humidity increased by 20%, and 1.3–2.5 times with the temperature increased by 5 °C, respectively. In agreement with the experimental treatment, a new method of estimating parameters was carried out in a theoretical model from formaldehyde emission, opening the way to a factorial analysis of the relevant parameters for relative humidity and temperature. The theoretical model with estimated parameters was further validated by experiments with different environmental conditions, which should help to quickly determine the parameters needed to predict formaldehyde emissions.

Improved C-history method for rapidly and accurately measuring the characteristic parameters of formaldehyde/VOCs emitted from building materials

The initial emittable concentration (C0), diffusion coefficient (Dm), and material/air partition coefficient (K) are the three characteristic parameters influencing emissions of formaldehyde and volatile organic compounds (VOCs) from building materials. In existing studies, two types of C-history methods (using either sealed or ventilated chambers) have been developed to simultaneously measure these three parameters. However, they both require the emission time (t) to be longer than a specific value, which may prolong the experimental time and reduce the method accuracy. In order to overcome this limitation, we propose an improved C-history method based on the completely analytical solution of the mass transfer model describing the VOC emission process. The improved method is validated by experimental results, proving that it is reliable and convincing. Finally, optimization of experiment conditions (e.g., air exchange rate and material load) and effects of experimental errors introduced by different sources are discussed and analyzed to improve the accuracy and stability of the improved method.

Alternately airtight/ventilated emission method: A universal experimental method for determining the VOC emission characteristic parameters of building materials

The volatile organic compound (VOC) emissions of building materials are characterized by three key parameters: the initial emittable concentration (C0), the partition coefficient (K), and the diffusion coefficient (D). Accurate determination of these three parameters is the basis for understanding VOC emission characteristic and the prerequisite for determining appropriate control strategies. In this paper, an alternately airtight/ventilated emission (AAVE) method for efficient and accurate determination of VOC emission characteristic parameters of building materials is proposed. By switching the airtight/ventilated emission mode of the building material samples, the equilibrium concentration in the airtight state and the dynamic concentration in the ventilation state were measured. K and C0 can be simply calculated by linear fitting of experimental data. Compared to the multi-emission/flush regression method and the variable volume loading method, the AAVE method requires less pre-adjustment process and has a wide measurement range. Compared to the two remarkably efficient measurement methods, the closed/ventilated chamber C-history methods, the AAVE method requires fewer intermediate parameters, simpler calculation process, and has a better error tolerance to the process data. The formaldehyde emission characteristic parameters of four types of building materials were measured using the AAVE method and verified by independent experiment. The experimental results indicated the reliability of the AAVE method. Finally, an optimized selection method of the ventilation parameters is proposed for adapting to the characteristic parameter measurement of various building material-VOC pairs.

Predicting VOC emissions from materials in vehicle cabins: Determination of the key parameters and the influence of environmental factors

Emission of volatile organic compounds (VOCs) from materials in vehicle cabins is one of the main reasons for poor in-cabin air quality. The emission behaviors can be characterized by key parameters including the initial emittable concentration (C0) and the diffusion coefficient (Dm). Determination of these parameters provides a foundation for predicting emissions and evaluating driver and passenger exposures. By analyzing VOC emissions from in-cabin materials under ventilated conditions, we propose a novel method to simultaneously determine C0 and Dm. This method initially establishes a linear correlation between the logarithm of excess VOC concentration and emission time, then the key parameters C0 and Dm are obtained by linear curve fitting and solving two equations. Using this method we determined the C0 and Dm for five VOCs (benzene, toluene, p-xylene, ethylbenzene and styrene) emitted from a common in-cabin material under different environmental conditions. Good agreement between the predicted VOC concentrations based on the measured key parameters and experimental data demonstrates the effectiveness of this method. Moreover, the impact of temperature on C0 was investigated for the five VOCs. Results indicated that C0 of all the studied VOCs increased with an increase in temperature, and toluene showed the greatest increase. When the temperature increased from 25°C to 50°C at the relative humidity of 50%, the C0 of toluene increased by 1.07 fold.