Abstract
Mass transfer models are useful in predicting the emissions of volatile organic compounds (VOCs) and formaldehyde from building materials in indoor environments. They are also useful for human exposure evaluation and in sustainable building design. The measurement errors in the emission characteristic parameters in these mass transfer models, i.e., the initial emittable concentration (C 0), the diffusion coefficient (D), and the partition coefficient (K), can result in errors in predicting indoor VOC and formaldehyde concentrations. These errors have not yet been quantitatively well analyzed in the literature. This paper addresses this by using modelling to assess these errors for some typical building conditions. The error in C 0, as measured in environmental chambers and applied to a reference living room in Beijing, has the largest influence on the model prediction error in indoor VOC and formaldehyde concentration, while the error in K has the least effect. A correlation between the errors in D, K, and C 0 and the error in the indoor VOC and formaldehyde concentration prediction is then derived for engineering applications. In addition, the influence of temperature on the model prediction of emissions is investigated. It shows the impact of temperature fluctuations on the prediction errors in indoor VOC and formaldehyde concentrations to be less than 7% at 23±0.5°C and less than 30% at 23±2°C.
Highlights
Chemical pollutant emissions from building materials in indoor environments can result in adverse health effects on indoor occupants [1,2]
The predicted emission rates of volatile organic compounds (VOCs)/formaldehyde using different emission models for a single layer homogeneous building material differ mainly during the initial stage when the dimensionless mass transfer time, Fourier number (Fom~ DL2t, where, D is the diffusion coefficient, t is time, and L is the thickness of the building material), is less than 1024, but are similar when used for long term prediction [5,6,7]
Three emission characteristic parameters need to be measured in advance for model predictions: the diffusion coefficient of VOCs/formaldehyde in building material, D (m2/s); the material/ air phase partition coefficient, K (2); and the initial emittable VOC/formaldehyde concentration, C0
Summary
Chemical pollutant emissions from building materials in indoor environments can result in adverse health effects on indoor occupants [1,2]. Analytical emission models predicting VOC/ formaldehyde emissions provide an efficient way to evaluate the short and long term emissions of VOCs/formaldehyde in various practical environmental conditions as compared to chamber studies of emissions. A series of mass transfer models have been developed based on different initial or boundary conditions to predict the emissions of VOCs/formaldehyde from building materials [3,4]. The predicted emission rates of VOCs/formaldehyde using different emission models for a single layer homogeneous building material differ mainly during the initial stage when the dimensionless mass transfer time, Fourier number (Fom~ DL2t, where, D is the diffusion coefficient, t is time, and L is the thickness of the building material), is less than 1024, but are similar when used for long term prediction [5,6,7].
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